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UNIVERSnTgrCALIFDRNIA 
COLLEGE  of  MINING 

DEPARTMENTAL 
LIBRARY 

BEQUEST  OF 

r  \ 

SAM  UELBENEDICrCHRlSTV 
PROFESSOR  OF 

MINING  AND   METALLURGY 
1885-1914 


ALUMINIUM. 


ALUMINIUM: 


ITS  HISTORY,  OCCURRENCE,  PROPERTIES, 

METALLURGY  AND  APPLICATIONS, 

INCLUDING  ITS  ALLOYS. 


JOSEPH  W.  RICHARDS,  M.A.,  A.C., 

INSTRUCTOR  IN   METALLURGY  AT   THE  LEHIGH   UNIVERSITY. 


SECOND  EDITION, 
REVISED  AND  GREATLY  ENLARGED. 

ILLUSTRATED  BY 

TWENTY-EIGHT  ENGRAVINGS  AND  TWO  DIAGRAMS, 


PHILADELPHIA: 
HENRY   CAREY  BAIRD   &   CO., 

INDUSTRIAL  PUBLISHERS,  BOOKSELLERS,  AND  IMPORTERS, 

810  WALNUT  STREET. 

1890. 


MIM1N<*    »»«•  FT. 


COPYRIGHT  BY 
JOSEPH  W.  RICHARDS, 

1890. 


PRINTED  AT  THE  COLLINS  PRINTING  HOUSE, 

705  Jayne  Street, 
PHILADELPHIA,  U.  8.  A. 


PREFACE  TO  T1IE  SECOND  EDITION. 


IF  it  was  true  that  no  apology  was  necessary  in  presenting 
a  work  on  Aluminium  in  English,  as  stated  in  the  preface  to  the 
first  edition  of  this  book,  it  is  equally  true  that  still  less  apology 
is  necessary  in  offering  an  improvement  on  that  work. 

The  present  volume  is  designed  to  be  an  improvement  on 
the  former  one  in  the  following  respects :  Mistakes  have  been 
corrected  wherever  detected  by  the  author  or  pointed  out  by 
his  friends ;  in  some  instances  the  order  of  treatment  of  different 
parts  has  been  revised,  so  as  to  bring  them  into  strict,  logical 
sequence ;  the  more  strictly  historical  processes  are  described  in 
greater  detail,  in  order  to  preserve  a  complete  record  of  the  rise 
of  the  aluminium  industry ;  chapters  have  been  added  treating 
on  the  properties  and  the  preparation  of  aluminium  compounds, 
on  the  theoretical  aspect  of  the  reduction  of  aluminium  com- 
pounds, and  on  the  analysis  of  commercial  aluminium  and  its 
common  alloys ;  the  original  chapters  have  been  in  several  cases 
sub-divided,  and  every  part  treated  more  by  itself  and  in  greater 
detail  than  before;  finally,  additions  have  been  made  throughout, 
recording  and  describing  the  progress  achieved  in  the  last  three 
years,  with  a  completeness  which  it  is  hoped  is  up  to  the  stand- 
ard of  the  rest  of  the  book. 


vi  PREFACE  TO   THE   SECOND   EDITION. 

The  method  of  treatment  in  the  present  edition  will  be  found 
to  be  more  critical,  for  wherever  a  reasonable  doubt  might  be 
expressed  as  to  the  correctness  of  certain  claims,  or  a  rational 
explanation  advanced  for  certain  phenomena,  the  author  has  not 
hesitated  to  put  his  best  thought  on  the  question  and  to  state 
his  conclusions  unreservedly. 

The  friendly  criticisms  of  the  scientific  press  and  their  sug- 
gestions have  been  kept  in  view  in  preparing  this  new  edition. 
The  spelling  "aluminium"  has  been  retained,  because  no  sufficient 
reasons  have  been  advanced  for  changing  it  to  "  aluminum ;"  and 
even  if  each  way  was  equally  old  and  as  well-sanctioned  by 
usage  and  analogy  as  the  other,  the  author's  choice  would  be  the 
longer  spelling,  as  being  more  euphonious  and  agreeable  to  the 
ear. 

It  has  been  the  author's  endeavor  to  make  this  volume  as 
complete  as  possible,  as  accurate  as  possible,  to  write  it  in  a 
manner  which  will  be  entertaining  to  the  general  reader,  and  to 
furnish  a  treatise  which  will  be  of  practical  value  to  the  practical 
metallurgist  as  well  as  of  scientific  merit  where  it  touches  on 
matters  of  theory. 

J.  W.  K. 

BETHLEHEM,  PA.,  March  12,  1890. 


PREFACE  TO  THE  FIRST  EDITION. 


No  apology  is  necessary  in  presenting  a  work  on  aluminium 
in  English.  In  1858  Tissier  Bros,  published  in  France  a  small 
book  on  the  subject.  H.  St.  Claire  Deville,  the  originator  of 
the  aluminium  industry,  published  a  treatise,  also  in  French,  in 
1859.  Deville's  book  is  still  the  standard  on  the  subject.  Until 
December,  1885,  we  have  an  intermission,  and  then  a  work  by 
Dr.  Mierzinski,  forming  one  of  Hartleben's  Chemisch-Technische 
Bibliothek,  which  is  a  fair  presentation  of  the  industry  up  to 
about  1883,  this  being  a  German  contribution.  Probably  be- 
cause the  English  speaking  people  have  taken  comparatively 
little  hand  in  this  subject  we  find  no  systematic  treatise  on 
aluminium  in  our  language.  The  present  work  aims  to  present 
the  subject  in  its  entirety  to  the  English  reader. 

Tissier,  Deville,  Mierzinski,  and  the  German,  French,  and 
English  scientific  periodicals  have  been  freely  consulted  and 
extracted  from,  full  credit  being  given  in  each  case  to  the  author 
or  journal.  As  this  art  has  of  late  advanced  so  rapidly  it  has 
been  a  special  aim  to  give  everything  that  has  been  printed  up 
to  the  time  of  publication. 

The  different  parts  of  the  work  are  arranged  in  what  seemed 
their  logical  order,  corresponding  closely  to  that  followed  by 


Vlll  PREFACE   TO   THE    FIRST   EDITION. 

Deville.  The  Appendix  contains  an  account  of  laboratory 
experiments,  etc.,  several  of  which,  it  is  trusted,  may  be  of 
value. 

In  conclusion,  the  author  wishes  to  thank  the  faculty  of  his 
"  Alma  Mater,"  Lehigh  University,  for  their  permission  to  use 
his  Thesis  on  Aluminium  as  the  basis  of  this  treatise ;  also, 
to  acknowledge  his  indebtedness  to  Dr.  Wm.  H.  Greene,  of 
Philadelphia,  for  assistance  rendered  in  the  preparation  of  the 
work  for  the  press. 

J.  W.  R. 

PHILADELPHIA,  November  25,  1886. 


ABBREVIATIONS  USED  IN  MAKING  REFERENCES. 


Deville De  1' Aluminium.      H.    St.   Claire  Deville. 

Paris,  1859. 
Fremy Encyclopedic    Chimique.      Fremy.      Paris, 

1883. 
Kerl  and  Stohman    ....     Enclyclopadisches    Handbuch   der    Techni- 

schen  Chemie.     4th  Ed. 
Mierzinski Die  Fabrikation  des  Aluminiums.    Dr.  Mier- 

zinski.     Vienna,  1885. 
Tissier Recherche  de  1' Aluminium.     C.  &  H.  Tis- 

sier.     Paris,  1858. 
Watts Watts' s  Dictionary  of  Chemistry,  vol.  i. 


Ann.  de  Chim.  et  de  Phys.    .     Annales  de  Chimie  et  de  Physique. 

Ann.  der  Chem.  und  Pharm.  1  Liebig's  Annalen  der  Chemie  und  Phar- 
Liebig's  Ann.  j  macie. 

Bull,  de  la  Soc.  Chim.       .     .     Bulletin  de  la  Soci6t6  Chimique  de  Paris. 

Chem.  News The  Chemical  News. 

Chem.  Zeit.    ...*...     Chemiker  Zeitung  (Cothen). 

Compt.  Rend Comptes  Rendus  de  les  Seances  de  1' Acade- 
mic. Paris. 

Dingl.  Joul Dingier' s  Polytechnisches  Journal. 

E.  and  M.  J The  Engineering  and  Mining  Journal. 

Jahresb.  der  Chem.  .  .  .  Jahresbericht  ueber  die  Fortschritte  der 

Chemie. 

Jrnl.  Chem.  Soc Journal  of  the  Chemical  Society. 

Jrnl.  der  Pharm Journal  der  Pharmacie. 

Jrnl.  fur  pr.  Chem.        .     .     .     Erdmann's  Journal  ftir  praktische  Chemie. 

Mon.  Scientif. Le  Moniteur  Scientifique.  Dr.  Quesnes- 

ville. 

Phil.  Mag The  London  and  Edinburgh  Philosophical 

Magazine. 

Phil.  Trans Transactions  of  the  Royal  Philosophical 

Society. 

Pogg.  Ann PoggendorfPs  Annalen. 


ABBREVIATIONS   USED   IN   MAKING   REFERENCES. 


Poly.  Centr.  Blatt. 
Proc.  Ac.  Nat.  Sci. 

Quarterly  Journal    . 
Rpt.  Brit.  A.  A.  S.      . 

Sci.  Am.  (Suppl.). 
Wagner's  Jahresb.  .     . 

Zeit.  fur  anal.  Chem. 


Polytechnisches  Central-Blatt. 

Proceedings    of    the    Academy   of  Natural 

Science  (Philadelphia). 
Quarterly  Journal  of  the  Society  of  Arts. 
Report  of  the  British  Association  for   the 

Advancement  of  Science. 
Scientific  American  (Supplement). 
Wagner's   Jahresbericht   der    Chemischen 

Technologic. 
Zeitschrift  fur  Analytische  Chemie. 


CONTENTS. 


CHAPTER  I. 

HISTORY   OF   ALUMINIUM. 

PAGE 

Lavoisier's  suggestion  of  the  existence  of  metallic  bases  of  the  earths 
and  alkalies  ;  Researches  in  the  preparation  of  aluminium  by  Davy, 
Oerstedt,  and  Wohler  ;  Isolation  of  aluminium  by  Wohler  .  .  17 

Isolation  of  almost  pure  aluminium  by  H.  St.  Claire  Deville,  in  1854; 
Method  of  Deville's  researches  .  .  .  .  .  .  .18 

Deville's  paper  on  "Aluminium  and  its  Chemical  Combinations;"  M. 
Thenard's  recommendation ;  Pecuniary  assistance  given  Deville  by 
the  French  Academy  ;  M.  Chenot's  claim  to  priority  of  invention  ; 
Deville's  experiments  at  the  Ecole  Normale  ;  Reduction  of  alumin- 
ium chloride  by  the  battery 19 

Deville  and  Debray's  experiments  in  the  manufacture  of  sodium ; 
Manufacture  of  metallic  sodium  at  Rousseau  Bros.'  chemical  works 
at  Glaciere,  and  enormous  reduction  in  its  price ;  Deville's  descrip- 
tion of  his  electrolytic  methods 20 

Experiments  in  the  manufacture  of  aluminium  at  the  expense  of 
Napoleon  III.  ;  Experiments  of  Chas.  and  Alex.  Tissier  on  the 
production  of  sodium  ;  Deville's  experiments  at  Javel  .  .  .21 

Aluminium  at  the  Paris  Exhibition,  1855  ;  First  article  made  of  alu- 
minium ;  Dispute  between  the  Tissiers  and  Deville  about  a  sodium 
furnace  .  .  .  .  .  .  .  .  .  .  .22 

Foundation  of  aluminium  works  by  M.  Chanu  at  Rouen ;  History  of 
the  works  at  Rouen  as  described  by  the  Tissiers ;  The  process  finally 
used  at  Amfreville  .........  23 

Manufacture  of  aluminium  on  a  large  scale  at  Glaciere,  Nanterre,  and 

Salindres  ;  Tissier  Bros.'  book  on  aluminium  in  1858        ...       24 

Deville's  book,  1850  ;  His  explanation  of  the  uses  of  the  new  metal ; 
Dr.  Percy's  and  H.  Rose's  experiments 25 

Alfred  Monnier's  production  of  sodium  and  aluminium  at  Camden, 
N.  J.  ;  W.  J.  Taylor  claiming  the  possible  cost  of  aluminium  at  $1 
per  pound  ;  First  aluminium  works  in  England,  1859  ...  26 


Xll  CONTENTS. 

PAGE 

Bell  Bros.'  aluminium  works  at  Newcastle-on-Tyne,  1860  ;  Price  of  alu- 
minium manufactured  by  them  ;  Aluminium  industry  in  Germany  ; 
Dr.  Clemens  Winckler's  retrospect  of  the  development  of  the  alu- 
minium industry,  1879  .........  27 

Prices  of  aluminium  and  aluminium  bronze  in  France,  1878  ;  Webster's 
aluminium  works  in  England,  1882;  Mr.  Walter  Weldon  on  the 
prospects  of  the  aluminium  industry,  1883 28 

Improvements  in  the  manufacture  outlined  by  Mr.  Weldon  .         .       29 

Reduction  in  the  cost  of  aluminium  in  1882,  by  Mr.  Webster's  inven- 
tions;  Organization  of  the  "  Aluminium  Crown  Metal  Company" 
at  Hollywood,  near  Birmingham ;  Mr.  H.  Y.  Castner's  new  sodium 
process,  1886 30 

Mr.  Castner's  patent  the  first  granted  on  that  subject  in  the  United 
States  ;  Combination  of  the  Castner  and  Webster  processes,  in  Eng- 
land; Works  at  Oldbury  near  Birmingham,  1888  ....  31 

Revolutions  in  the  aluminium  industry  since  1884  ;  Revival  of  the  old 
methods  of  electrolysis  discovered  by  Deville  and  Bunsen ;  Gratzel's 
process  patented  in  Germany,  1883  .  \.  .  .  .  .32 

Mr.  Saarburger's  process ;  Process  patented  by  Dr.  E.  Kleiner,  of 
Zurich,  1886  ;  Electrolytic  method  of  Mr.  Chas.  M.  Hall,  of  Ober- 
lin,  O.,  patented  in  the  United  States,  April,  1889  ;  Price  of  alu- 
minium made  by  the  process  ........  33 

Difference  in  electrolytic  processes ;  SirW.  Siemens'  electric  furnace  ; 
Mr.  Ludwig  Grabau's  experiments  in  the  reduction  of  alumina, 
1882  ;  Dr.  Mierzinski  remarks  on  the  use  of  the  electric  furnace  .  34 

Cowles'  Electric  Smelting  and  Aluminium  Company,  Lockport,  N.  Y.  ; 
Works  in  England  and  the  United  States  sprung  from  the  Cowles 
process  ;  The  principle  made  use  of  in  the  Cowles  process        .         .       35 
Difference  in  the  products  obtained  by  the  various  electrolytic  methods  ; 
The  Heroult  process ' .         .         .         .36 

Manufacture  of  aluminium  by  the  Heroult  process  in  Switzerland, 
France,  and  the  United  States ;  Comparison  of  the  Cowles  and 
Heroult  processes  .  .  .  .  .  .  .  .  .  .37 

The  Alliance  Aluminium  Company  of  London,  England,  and  the 
patents  and  methods  used  by  it ;  Prof.  Netto's  method  of  producing 
sodium ;  Cost  of  aluminium  produced  by  the  Alliance  Company  ; 
The  "  Alkali  Reduction  Syndicate,  Limited"  ....  38 

Ludwig  Grabau's  improvements  in  producing  aluminium  ;  "  The  Amer- 
ican Aluminium  Company"  of  Milwaukee,  Wis.  ;  Prof.  A.  J. 
Rogers's  process ;  Inaccurate  statements  inspired  by  a  company 

hailing  from  Kentucky 39 

Production  of  iron  castings  containing  aluminium  ;  Col.  Win.  Frish- 
muth's  works  in  Philadelphia  .  .  .  .  .  .  .40 


CONTENTS.  Xlll 

PAGE 

Col.  Frishmuth's  patents  and  methods;  Quality  of  the  metal  pro- 
duced by  Col.  Frishmuth  .  .  .  .  .  .  .  .41 

Census  report  on  Col.  Frishmuth's  annual  production ;  Aluminium 
casting  for  the  Washington  Monument,  made  by  Col.  Frishmuth; 
"The  Aluminium  Company  of  America;"  The  United  States 
Aluminium  Company  of  East  St.  Louis  ;  Aluminium  exhibits  at  the 
Paris  Exposition,  1889  .  .  .' 42 

Detailed  account  of  the  exhibits ;  Great  advances  in  the  aluminium 
industry  shown  by  the  exhibit  .......  43 

Statistical;  Prices  of  aluminium  from  1856  to  1889;  Prices  of  10  per 
cent,  aluminium  bronze  from  1878  to  1888 ;  Annual  outputs  of 
aluminium  from  1854  to  1887  .......  44 

Estimate  of  aluminium  produced  up  to  1886  ;  Amount  produced  since 
1886  ;  Aluminium  imported  into  the  United  States  from  1870  to  1888  45 

CHAPTER   II. 

OCCURRENC^  OF   ALUMINIUM   IN   NATURE. 

Wide  distribution  of  aluminium ;  Combinations  of  aluminium  with 
oxygen,  the  alkalies,  fluorine,  etc.  ;  Non-occurrence  of  aluminium  in 
animals  and  plants ;  Appearance  of  most  of  the  aluminium  com- 
pounds ;  Formulas  of  some  aluminium  compounds  classed  as  precious 
stones  ............  46 

Formulas  of  frequently  occurring  compounds  of  aluminium ;  Minerals 
most  used  for  producing  aluminium  ;  Beauxite  ;  Analyses  of  beauxite  47 

Index  to  analyses  of  beauxite     .         .         .         .         .         .         .         .48 

Deposit  of  beauxite  in  Floyd  County,  Georgia,  with  analyses       .         .       49 

Cryolite ;  Where  found,  description,  general  uses,  and  analyses ;  Im- 
portation of  cryolite  by  the  Pennsylvania  Salt  Company  of  Phila- 
delphia, 1887 50 

Deposit  of  cryolite  in  the  United  States  ;  Minerals  associated  with  it ; 
Corundum;  Discovery  of  it  in  the  United  States,  in  1869,  by  Mr. 
W.  P.  Thompson ;  Production  of  corundum  in  the  United  States  in 
1887 '  .  51 

Native  sulphate  of  alumina ;  Discovery,  description,  and  analysis  of 
"native  alum"  from  the  Gila  River,  Sorocco  County,  New  Mexico  52 

CHAPTER   III. 

PHYSICAL   PROPERTIES   OF   ALUMINIUM. 

What  must  be  understood  by  the  properties  of  aluminium  ;  The  most 
frequent  impurities  of  commercial  aluminium 53 

The  r61e  of  silicon  in  aluminium  ;  Table  of  analyses  of  commercial 
aluminium  .........  .54 


XIV  CONTENTS. 

PAGE 

Notes  on  the  analyses;  Combined  and  free  silicon  in  aluminium; 
Analyses  of  aluminium  reduced  from  cryolite  by  sodium  .  .  55 

Analysis  of  aluminium  by  Prof.  Rammelsberg ;  Gases  in  aluminium ; 
Color 56 

Appearance  of  Grabau's  and  ordinary  commercial  aluminium ;  Influ- 
ence of  iron  and  copper  on  the  color  of  aluminium  ;  Removal  of  dis- 
coloration caused  by  damp  air ;  Explanation  of  the  greater  promi- 
nence of  the  blue  tint  after  the  metal  has  been  worked  ...  57 

Fracture ;  Peculiarities  in  the  fracture  of  the  purest  varieties  of  alu- 
minium ;  Increase  in  the  fibrousness  of  the  metal  by  working ; 
Hardness ;  Its  increase  by  the  presence  of  impurities  ...  58 

Testing  aluminium  with  the  knife  ;  Specific  gravity ;  Of  commercial 
aluminium ;  Comparison  of  analyses  and  specific  gravities  .  .  59 

Contraction  in  the  volume  of  aluminium  by  alloying ;  Increase  in  the 
density  of  aluminium  by  being  worked  ;  Comparison  of  the  specific 
gravity  of  aluminium  with  that  of  other  metals  60 

Comparative  value  of  equal  volumes  of  aluminium  and  silver ;  Fusi- 
bility ;  Determination  of  the  melting  point  by  Pictet,  Heeren,  Van 
der  Weyde,  and  Prof.  Carnelley  .  .  .  .  .  .  .61 

Volatilization  ;  Deville  on  this  subject ;  In  electric  furnace  processes  ; 
Odor;  Taste 62 

Magnetism ;  Deville,  MM.  Poggendorff  and  Reiss ;  Sonorousness ; 
Results  obtained  by  Deville  and  M.  Lissajous  in  making  bells  and 
tuning  forks ;  Results  obtained  by  Mr.  Faraday  ;  Verification  of  Mr. 
Faraday's  observations  . 63 

Crystalline  form;  As  observed  by  Deville;  Elasticity;  Deville,  M. 
Wertheim  and  Mallet  on  this  subject  ......  64 

Tenacity ;  Results  obtained  by  W.  H.  Barlow  ;  Comparative  mechani- 
cal value  of  aluminium  and  steel ;  Results  as  to  the  strength  of 
aluminium  wire  obtained  by  Kamarsch  .  .  .  .  .  .65 

Malleability;  Aluminium  leaf  first  made  by  M.  Degousse,  of  Paris,  and 
C.  Falk  &  Co.,  of  Vienna;  Thickness  of  commercial  leaf  .  .  66 

Forging,  hammering,  and  shaping  of  aluminium  ;  Ductility  ;  Manufac- 
ture of  aluminium  wire  ;  Expansion  by  heat ;  Fizeau's  coefficients 
of  linear  expansion  of  aluminium  by  heat  .  .  .  .  .67 

Specific  heat ;  Deville,  M.  Regnault,  Kopp,  Mallet,  and  Nacarri  on 
this  subject ;  Determination  of  the  latent  heat  of  fusion  by  Mr.  J. 
W.  Richards ;  Electric  conductivity ;  Results  obtained  by  Deville 
and  Buff,  M.  Margottet,  Prof.  Mattheisen,  and  Benoit  .  .  68 

Comparison  of  the  various  results ;  Thermal  conductivity ;  Deville, 
Faraday,  and  Calvert  and  Johnson  on  this  subject  ....  70 


CONTENTS.  XV 


CHAPTER  IV. 

CHEMICAL  PROPERTIES   OF   ALUMINIUM. 

PAGE 

Remark  ;  Action  of  air ;  Deville,  Wohler,  and  M.  Peligot  on  this  sub- 
ject-  71 

"Dead"  appearance  of  aluminium   objects;  Burning  of  aluminium; 

Wohler' s  observations 72 

Action  of  water ;  Decomposition  of  aluminium  leaf  by  water  ;  Action  of 
hydrogen  sulphide  and  sulphur         •    »    •         •         •         •         •         .73 

Resistance  of  aluminium  to  the  vapor  of  sulphur ;  Absorption  of  hy- 
drogen sulphide  by  molten  aluminium  ;   Sulphuric  acid     .         .         .74 
Nitric  acid ;  Hydrochloric  acid     .         .  .         .         .         .75 

Organic  acids,  vinegar,  etc.         .         .         .         .         .         .         .         .76 

Tin  more  attacked  by  organic  acids  than  aluminium  ;  Chief  cause  of  the 
tarnishing  of  polished  aluminium  articles  ;  Ammonia  ;  Caustic  alka- 
lies   77 

Solutions  of  metallic  salts   .........       78 

Precipitation  of  other  metals  by  aluminium          .  .         .         .79 

Reduction  of  metallic  chlorides  by  aluminium ;  Action  of  aluminium 
on  alkaline  chlorides  ;  action  of  aluminium  salts  on  aluminium  ;  Sod- 
ium chloride;  Salt  as  a  flux  for  aluminium;  Fluorspar;  As  a  flux 

for  the  metal 80 

Cryolite ;  Its  action  on  aluminium  ;  Silicates  and  borates  ;  Their  action 

on  aluminium  ;  Nitre ;  Deville  on  this  subject          ....       81 
Purification  by  nitre ;    Alkaline  sulphates  and  carbonates  ;    Metallic 

oxides  ;  Tissier  Brothers'  experiments 82 

Beke"toff's  experiment;  Miscellaneous  agents 83 

General  observations  on  the  properties  of  aluminium,  Deville       .         .       84 

CHAPTER  Y. 

PROPERTIES   AND   PREPARATION   OP   ALUMINIUM   COMPOUNDS. 

General  considerations ;  Structure  of  aluminium  compounds  ;  Chemical 
position  of  aluminous  salts  ........  85 

Neutral  and  basic  salts  of  aluminium  ;  Aluminium  oxyhydrate ;  General 

methods  of  formation  and  properties  ;  Solubility  of  aluminium  salts  86 

Reaction  of  neutral  solutions  of  aluminium  salts ;  Aluminium  oxide ; 
Composition  and  description  of  alumina  ......  87 

Aluminium  hydrates ;  Diaspore,  Beauxite,  and  Gibbsite ;  Artificial 
hydrates  ;  Formula  and  description  of  the  insoluble  modification  .  88 

Aluminates  ;  Potassium  aluminate ;  Sodium  aluminate  ;  Barium  alumi- 
nate 89 

Calcium  aluminate,  zinc  aluminate,  copper  aluminate,  magnesium  alumi- 
nate ;  Aluminium  chloride 90 


XVI  CONTENTS. 

PAGE 

Properties  of  aluminium  chloride ;    Aluminium-sodium  chloride ;    Its 

properties        ...........  91 

Aluminium-phosphorus   chloride ;    Aluminium-sulphur  chloride ;    Alu- 
minium-selenium chloride  ;  Aluminium-ammonium  chloride     .          .  92 
Aluminium-chlor-sulphydride ;    Aluminium-chlor-phosphydride ;    Alu- 
minium bromide 93 

Aluminium  iodide;   Aluminium  fluoride;  Its  first  production  by  De- 

ville  ;   Volatilization  of  aluminium  fluoride       .....  94 

Aluminium  fluorhydrate  ;  Aluminium-hydrogen  fluoride  ;   Aluminium- 
sodium  fluoride        .         .         .     '    .         .         .         .         .         .         .95 

Aluminium  sulphide  ;  Aluminium  selenide  ;  Aluminium  borides          .  96 

Borides  obtained  by  Hampe 97 

Aluminium  nitride  ;  Aluminium  sulphate;  Anhydrous;  Hjdrated      .  98 

Halotrichite ;  Basic  aluminium  sulphate      ......  99 

Alums  ;  Definition  of  alums  ;  Potash  alum  ;  Calcined  alum         .         .100 

Alunite;  Ammonia  alum;   Soda  alum ;  Aluminium-metallic  sulphates  101 

Aluminium  selenites ;   Aluminium  nitrate  ;  Aluminium  phosphates      .  102 
Wavellite  ;    Kalait ;     Turquois  ;     Aluminium   carbonate  ;     Aluminium 

borate  ;  Formation  of  crystals  of  corundum  ;   Aluminium  silicates     .  103 

Disthene  ;  Andalusite  ;  Fibrolite;  Kaolin;  Orthoclase  ;  Common  clays  104 

CHAPTER  VI. 

PREPARATION   OP   ALUMINIUM   COMPOUNDS   FOR   REDUCTION. 

Preparation  of  alumina  from  alums  and  aluminium  sulphate  ;  Its  com- 
position ...........  105 

Various  methods  of  preparing  alumina;  Deville's  method  used  at 
Javel 106 

Tilghman's  method  of  preparing  alumina    .         .         .         .         .         .107 

Mr.  Webster's  process  for  making  pure  alumina  .....     108 

Preparation  of  alumina  from  beauxite ;  Occurrence  of  beauxite  in 
France ;  Deville's  process  as  used  at  Salindres,  illustrated  and  de- 
scribed   109 

Composition  of  alumina  prepared  by  Deville's  process;  Behnke's 
method;  Proposed  treatment  of  beauxite,  etc.,  by  R.  Lieber ;  H. 
Muller's  method  of  extracting  alumina  from  silicates  .  .  .113 

Action  of  common  salt  on  beauxite ;  Treatment  of  beauxite  proposed 
by  R.  Wagner;  Lowig's  experiments  with  solution  of  sodium  alumi- 
nate;  Dr.  K.  J.  Bayer's  improvement  in  the  process  of  extracting 
alumina  from  beauxite 114 

Preparation  of  alumina  from  cryolite  ;  By  the  dry  way  ;  Julius  Thom- 
son's method  illustrated  and  described  .  .  .  .  .  .115 

Formula  according  to  which  the  decomposition  takes  place  in  Thomson's 
process  .  .  .  .  .  .  .  .  .  .  .  ,116 


CONTENTS.  XV11 

PAGE 

"  Levisseur  methodique"    .         .         .         .         .         .         .         .         .117 

Preparation  of  the  carbon  dioxide  for  precipitating  the  hydrated 
alumina ;  Precipitation  with  carbonic  acid  gas  ;  Composition  of  the 
precipitate;  Separation  of  the  sodium  carbonate  .  .  .  .118 

Utilization  of  aluminous  fluoride  slags  5  Deville's  process  used  at  Nan- 
terre ;  Analysis  of  the  residue  .  .  .  .  .  .  .119 

Decomposition  of  cryolite  in  the  wet  way ;  Deville's  method  used  at 
Javel 120 

Modification  of  Deville's  method  by  Sauerwein ;  Tissier's  and  Hahn's 
methods;  Reactions  involved  in  Hahn's  process;  Decomposition  of 
cryolite  in  the  establishment  of  Weber,  at  Copenhagen  .  .  .121 

Schuch's  method  ;  The  preparation  of  aluminium  chloride  and  alumin- 
ium-sodium chloride;  Wohler's  method  of  preparing  aluminium 
chloride 122 

Deville's  processes  for  the  production  and  purification  of  aluminium 
chloride  ;  Manufacture  on  a  small  scale  illustrated  and  described  .  123 

Manufacture  on  a  large  scale  illustrated  and  described.          .         .         .124 

Purification  of  aluminium  chloride      .         .         .         .         .         .         .126 

Apparatus  for  the  purification  of  aluminium  chloride  used  at  Salindres, 
illustrated  and  described  .  .  .  .  .  .  .  .127 

Cost  of  aluminium-sodium  chloride  by  Deville's  process  as  made  by 
Wurtz  in  1872  ;  Plant  of  the  Aluminium  Co.,  L't'd,  for  the  manu- 
facture of  aluminium-sodium  chloride  .  .  .  .  .  .129 

Chlorine  plant  of  the  Aluminium  Co.,  L't'd 130 

Amount  of  double  chloride  required  for  the  production  of  1  Ib.  of  alu- 
minium ;  Necessity  of  preventing  iron  from  contaminating  the  salt  .  131 

Castner's  process  for  purifying  the  double  chloride  ;  On  what  the  suc- 
cess of  the  manufacture  of  the  double  chloride  depends;  Quantities 
of    materials   required  for  the  production   of    100  Ibs.    of    double 
chloride  .         .         .         ... 132 

H.  A.  Gadsden's  method  of  obtaining  aluminium  chloride ;  Count  A. 
de  Montgelas's  process  ;  Prof.  Chas.  F.  Mabery's  process  .  .  133 

Mr.  Paul  Curie's  plan  of  making  aluminium  chloride;  H.  W.  War- 
ren's process;  Camille  A.  Faure's  process  .....  134 

The  aim  of  Mr.  Faure's  process;  Estimated  cost  of  the  chloride  by 
Mr.  Faure's  process 135 

M.  Dullo's  method  of  producing  aluminium  chloride  ....     136 

The  preparation  of  aluminium  fluoride  and  aluminium-sodium  fluoride 
(cryolite)  ;  Berzelius's  plan  of  preparing  artificial  cryolite  ;  Deville's 
statements 137 

Pieper's  process  of  preparing  artificial  cryolite;  Bruner's  method  of 
producing  aluminium  fluoride  ........  138 

Deville's  and   Hautefeuille's  method  of  making  aluminium  fluoride; 
Lud wig  Grabau's  process;  Reactions  outlining  this  process        .         .     139 
B 


XV111  CONTENTS. 

PAGE 

Method  of  obtaining  aluminium  fluoride  in  practice  ;  The  preparation  of 
aluminium  sulphide  ;  M.  Fremy's  researches  on  this  subject  .  .  140 

Keichel's  experiments  on  the  preparation  of  aluminium  sulphide         .     142 

J.  W.  Richards's  experiments  on  the  production  and  reduction  of 
aluminium  sulphide;  M.  Comenge's  plan;  Messrs.  Reillon,  Mon- 
tague, and  Bourgerel's  patent  .  .  .  .  .  .  .143 

Petitjean's  plan  of  making  aluminium  sulphide  .         .         .         .         .144 

CHAPTER  VII. 

THE   MANUFACTURE   OF   SODIUM. 

The  manufacture  of  sodium  a  separate  metallurgical  subject         .         .144 
Davy  to  Deville  (1808-1855);  Sodium  first  isolated  by  Davy,  1808; 
Gay-Lussac,  Thenard,  Curaudau,  and  Brunner's  researches;  Donny 
and  Mareska's  condenser,  illustrated  and  described  .         .         .145 

Deville's  improvements  at  Javel,  1855;   His  attempts  to  reduce  the 
cost  of  producing  sodium  ;  Properties  of  sodium      ....     146 

Deville's  method  of  producing  sodium  ;  Composition  of  mixtures  used    .     147 
Properties  a  mixture  should  show ;  The  r61e  of  the  various  ingredients 
of  a  mixture    ...........     148 

Mixture  used  at  La  Glacifcre  and  Nanterre ;  Use  of  these  mixtures ; 
Cost  at  which  sodium  was  obtained  .         .         .         .         .         .149 

Apparatus  for  reducing,  condensing,  and  heating  ;  Manufacture  in  mer- 
cury bottles  ;  The  most  suitable  furnace,  illustrated  and  described  .  150 

The  condenser,  illustrated  and  described 151 

The  most  rational  form  of  condenser,  illustrated  and  described ;  Mode 
of  conducting  the  operation     .         .         .         ...         .         .         .152 

How  to  prevent  the  ignition  of  the  sodium  ;  Use  of  cast-iron  bottles  ; 
Continuous  manufacture  in  cylinders         .         .         .         .         .         .154 

Advantage  of  a  strong  preliminary  calcination  of  the  materials ;  Man- 
ner of  using  cold,  uncalcined  mixture  155 

Furnace,  illustrated  and  described       .         .         .         .         .         .         .156 

Mode  of  conducting  the  manufacture  of  sodium  in  cylinders          .         .157 
Tissier   Bros.'  method  of  procedure   (1856)  ;    Details  from  Tissier's 

"Recherche  de  1' Aluminium ;"  Mixtures  used         .  •  .         .     158 

Furnace  for  calcining  the  mixtures,  illustrated  and  described  ;  Further 

treatment  of  the  calcined  mixtures 159 

Mode  of  protecting  the  retorts ;  Manner  of  reducing  the  sodium  .     160 

Tissier's  method  of  cleaning  the  sodium  ;  Deville's  improvements  at  La 

Glaciere  (1857)  ;  Results  obtained  by  Deville           .         .         .         .161 
Reasons  for  unsuccessful  attempts ;  Cast-iron  vessels    .         .         .         .162 
Causes  of  an  unfavorable  result  with  cast-iron  vessels ;  Improvements 
used  at  Nanterre  (1859) 163 


CONTENTS.  XIX 

PAGE 

Construction  of  the  iron  tubes  used  ;  Cost  of  sodium  by  Deville's  pro- 
cess (1872)  .  .  .  164 

Minor  improvements  (1859-1888)  ;  R.  Wagner's  and  J.  B.  Thompson 
and  W.  White's  methods 165 

H.  S.  Blackmore's  process  of  obtaining  sodium;  O.  M.  Thowless's 
method;  G.  A.  Jarvis's  patent;  Castner's  process  (1886);  First 
public  announcement  of  this  process  .  .  .  .  .  .166 

Description  of  Castner's  process          .         .         .         .         .         .         .167 

Claims  made  by  Mr.  Castner  in  his  patent 168 

Erection  of  a  large  sodium  furnace  in  England  by  Mr.  Castner     .         .169 

Mr.  J.  MacTear's  description  of  the  furnace  ;  Preparation  of  the  com- 
pounds used  .  .  .  .  .  .  .  .  .  .  .170 

Mode  of  conducting  the  operation  ;  Crucible  and  furnace,  illustrated 

and  described  ;  Analysis  of  the  gas  disengaged  .  .  .  .171 

Analyses  of  the  residues     .         .         .         .         .         .         ..         .172 

Weight  and  further  treatment  of  the  residues  ;  Yield  obtained  ;  Aver- 
age time  of  distillation  ;  Capacity  of  furnace ;  Estimated  cost  of  the 
sodium  produced  .  .  .  .  .  .  .  .  .  .173 

Life  of  the  crucibles  ;  Reasons  for  the  cheap  production  of  sodium  by 
Mr.  Castner's  process  .  .  . 174 

Details  of  the  latest  plant  of  the  Aluminium  Co.,  L't'd,  by  Mr.  Wm. 
Anderson  and  Sir  Henry  Roscoe ;  Yield  of  sodium  in  twenty-four 
hours ;  Shape  of  the  condenser  .  .  .  .  .  .  .175 

Melting  and  preservation  of  the  sodium  ;  Temperature  of  the  furnace    .     176 

Average  duration  of  each  crucible;  Dr.  Kosman's  explanation  of  the 
reactions  taking  place  in  Castner's  process 177 

Netto's  process  (1887)  ;  Reaction  taking  place  in  this  process      .         .     178 

The  retort  used  in  Netto's  process,  illustrated  and  described  ;  Mode  of 
operating  .  .  .  .  .  .  .  .  .  .  .179 

Reduction  of  sodium  compounds  by  electricity  ;  Economical  value  of 
these  processes  ;  P.  Jablochoff's  apparatus  for  decomposing  sodium  or 
potassium  chlorides,  illustrated  and  described ;  Prof.  A.  J.  Rogers' s 
attempts  to  reduce  sodium  compounds  electrolytically  .  .  .  180 

Computation  of  the  amount  of  coal  required  to  produce  a  given  amount 
of  sodium  by  electrolysis 181 

Results  of  experiments  by  Prof.  Rogers 182 

CHAPTER   VIII. 

THE    REDUCTION    OF    ALUMINIUM    COMPOUNDS    FROM    THE    STANDPOINT 
OF    THERMAL   CHEMISTRY. 

The  proper  way  to  use  the  accumulated  thermal  data  in  predicting  the 

possibility  of  any  reaction  almost  unknown       .          .         .         .         .183 
Illustration  of  the  principal  barriers  in  the  way 184 


XX  CONTENTS. 

PAGE 

Influence  of  the  relative  masses  of  the  reacting  bodies  ;  Heat  gene- 
rated by  the  combination  of  aluminium  with  the  different  elements  .  185 

Theoretical  aspect  of  the  reduction  of  aluminium  ;  Table  showing  the 
heat  given  out  by  other  elements  or  compounds  which  unite  energeti- 
cally with  oxygen 186 

Impossibility  of  sodium  or  potassium  reducing  alumina;  Probable  im- 
possibility of  some  reactions  ..  .  .  .  .  .  .187 

Calculations  which  have  been  made  to  show  that  carbon  will  reduce 
alumina  at  a  temperature  10,000°  C 188 

Sources  of  error  in  the  calculation ;  Lowest  calculated  value  for  the 
temperature  of  reduction  of  alumina  ......  189 

Table  of  the  heat  developed  by  the  combination  of  some  of  the  ele- 
ments with  chlorine,  bromine,  or  iodine  190 

Reflections  on  the  table ;  Probable  substitutes  for  sodium  in  reducing 
aluminium  chloride  .  .  .  .  .  .  .  .  .191 

Heat  of  combination  of  fluorides ;  Discussion  of  the  thermal  relations 
of  aluminium  sulphide 192 

Affinity  of  the  metals  for  sulphur ;  Reactions  of  use  in  the  aluminium 
industry  ;  Deficit  of  heat,  which  has  to  be  made  up  in  the  conversion 
of  alumina  into  aluminum  chloride 193 

Hydrated  chloride  of  no  value  for  reduction  by  sodium         .         .         .194 

The  reaction  made  use  of  for  obtaining  aluminium  sulphide  ;  Compu- 
tation of  the  thermal  value  of  the  reaction  taking  place  in  the  con- 
version of  alumina  into  aluminium  sulphide  195 

CHAPTER  IX. 

REDUCTION    OF    ALUMINIUM    COMPOUNDS    BY    MEANS   OF    POTASSIUM   OR 

SODIUM. 

(Reduction  of  Chlorine  Compounds.) 

Oerstedt's  experiments  (1824) 196 

Oerstedt's  original  paper;    Wohler's  experiments  (1827);    Wb'hler's 

review  of  Oerstedt's  article 197 

Wohler's  method  of  producing  aluminium  .         .         .         .         .         .198 

Wohler's  experiments  (1845)     .         . 199 

Accuracy  of  Wb'hler's  results  ;  Deville's  experiments  (1854)       .         .  200 
Deville's  method  for  obtaining  aluminium  chemically  pure  in  the  labor- 
atory        201 

Deville's  methods  (1855)  ;   Mode  of  reducing  the  aluminium  chloride 

by  sodium  ;  Perfectly  pure  aluminium  ;  Pure  materials    .         .         .  202 
Influence  of  flux  or  slag ;  Influence  of  the  vessel ;  Reduction  by  solid 

sodium  ;  Apparatus,  illustrated  and  described           ....  203 


CONTENTS.  XXI 

PAGE 

Process  by  which  were  made  the  ingots  of  aluminium  sent  to  the  Paris 
Exhibition  (1855);  Nature  of  this  aluminium;  M.  Mulct's  "hard 
aluminium"  ...........  205 

Reduction  by  sodium  vapor ;  The  operation  as  conducted  by  Deville ; 
Deville's  process  (1859)  ;  Process  used  at  that  time  at  Nanterre  .  206 

Production  of  the  works  at  Nanterre  ;  Rationale  of  the  process  used   .     207 

Substitution  of  cyrolite  for  fluorspar ;  Reduction  on  the  bed  of  a  rever- 
beratory  furnace 210 

Dimensions  of  the  furnace  ;  Proportions  of  the  mixture  used  ;  Recov- 
ery of  alumina  from  the  slag  211 

Treatment  of  the  slag  ;  Contents  of  the  slag ;  Reason  why  aluminium 
absorbs  a  large  quantity  of  silicon  .  .  .  .  .  .  .212 

The  Deville  process  (1882)  ;  Aluminium  as  made  at  Salindres  by  A. 
R.  Pechiney  &  Co.,  successors  to  H.  Merle  &  Co 213 

Successive  operations  of  the  process,  and  chemical  reactions  involved ; 
Advances  made,  since  1859,  in  the  reduction  of  the  double  chloride 
by  sodium 214 

The  reduction  furnace,  illustrated  and  described  .         .         .         .215 

Expense  of  the  process       .         .         .         .         .         .         .         .         .216 

Niewerth's  process  (1883) 217 

Gadsden's  patent  (1883)  ;  Frishmuth's  process  (1884)  ;  Claims  made 
by  Col.  Frishmuth  in  his  patent  .  .  .  .  .  .  .218 

H.  von  Grousillier's  improvement  (1885)  ;  The  Deville-Castner  pro- 
cess as  operated  by  the  Aluminium  Co.,  L't'd  ;  Principle  of  this  pro- 
cess   219 

Description  of  the  works  at  Oldbury,  near  Birmingham,  England ; 
Mode  of  conducting  the  reduction 220 

Reaction  taking  place  in  the  process  ;  Yield  of  the  charge ;  Purity  of 
the  metal  221 


CHAPTER  X. 

REDUCTION   OF    ALUMINIUM   COMPOUNDS  BY   MEANS   OF    POTASSIUM    OR 

SODIUM  (continued). 
(Reduction  of  Fluorine  Compounds.} 

Rose's  experiments  (1855) 222 

Experiments  of  Percy  and  Dick  (1855)       .         .         .         .         .         .230 

Tissier  Bros.'  method  (1857) .         .234 

Advantages  claimed  by  Tissier  Bros.'  for  the  use  of  the  cryolite ;  Diffi- 
culties met  with  in  this  process         .......     235 

Wohler's  modifications  (1856)  ;  Gerhard's  furnace  (1858)  .         .         .     236 
Thompson  and  White's  patent  (1887)  ;  Hampe's  experiment  (1888)  ; 
Netto's  process  (1887) 237 


XX11  CONTENTS. 


Operations  of  the    Alliance    Aluminium  Co.,  of  London,   England; 

Production  of  sodium  by  Capt.  Cunningham's  process  .  .  .  238 

Dr.  Netto's  process 239 

Construction  and  operation  of  Dr.  Netto's  experimental  apparatus  at 

Krupp's  works  at  Essen 240 

Cost  of  aluminium  to  the  Alliance  Aluminium  Company ;  Ludwig 

Grabau's  process  for  the  reduction  of  aluminium  fluoride  by  sodium  241 

The  reaction  taking  place  in  the  process      .         .         .         .         .         .  242 

The  furnace  used  in  Grabau's  process,  illustrated  and  described  .  .244 

Summary  of  the  advantages  claimed  by  M.  Grabau  for  his  process  .  245 

Purity  of  M.  Grabau's  product 246 

CHAPTER  XI. 

REDUCTION   OF   ALUMINIUM   COMPOUNDS    BY   THE   USE   OF   ELECTRICITY. 

Principles  of  electro-metallurgy  applying  to  the  decomposition  of  alu- 
minium compounds  246 

Calculation  of  the  theoretical  intensity  of  current  necessary  to  over- 
come the  affinities  of  any  aluminium  compound  .  .  .  .247 

Utilization  of  such  calculations   ........     248 

Deposition  of  aluminium  from  aqueous  solutions  .          .  .     249 

Mr.  George  Gore's  experiments;  Messrs.  Thomas  and  Tilly's  process; 
M.  Corbelli's  mode  of  depositing  aluminium  .....  250 

J.  B.  Thompson  on  depositing  aluminium  on  iron,  steel,  etc. ;  Pro- 
cedure for  depositing  aluminium  on  copper,  brass,  or  German  silver 
recommended  by  George  Gore 251 

J.  A.  Jeancon's  process  for  depositing  aluminium  ;  Methods  of  M  A. 
Bertrand,  Jas.  S.  Haurd,  and  John  Braun ;  Dr.  Fred.  Fischer  on 
Braun's  proposition  .  .  .  .  .  .  .  .  .  252 

Apparatus  patented  by  Moses  G.  Farmer ;  Methods  of  M.  L.  Senet, 
Col.  Frishmuth,  Baron  Overbeck,  and  H.  Niewerth,  and  Herman 
Rienbold 253 

Summary  of  Count  R.  de  Montegelas's  patents  for  the  electrolysis  of 
aqueous  solutions  of  aluminium  .......  254 

Methods  of  procedure  patented  by  A.  Walker;  H.  C.  Bull's  proposi- 
tion for  manufacturing  aluminium  alloys  .....  255 

Methods  patented  by  C.  A.  Burghardt  and  W.  J.  Twining,  of  Man- 
chester, England  ;  Various  other  patents  taken  out  in  England  .  256 

Various  authorities  who  consider  that  aluminium  cannot  be  deposited 
by  electricity  in  the  wet  way  ;  Letter  on  this  subject  from  Dr.  Justin 
D.  Lisle,  of  Springfield,  0 257 

The  electric  decomposition  of  fused  aluminium  compounds ;  The 
different  ways  of  operating ;  Davy's  experiments  (1810)  .  .  258 


CONTENTS.  XX111 

PAGE 

Duvivier's  experiment  (1854)  ;  Bunsen's  and  Deville's  methods  (1854)  ; 

Deville's  description  of  the  process           ......  259 

The  apparatus  used  by  Deville,  illustrated  and  described      .         .         .  260 
Arrangement  adopted   by   Bunsen ;    Plating   aluminium    on   copper  ; 

Capt.  Caron  and  Deville's  experiments    .         .         .         .         .         .262 

Le  Chatellier's  method  (1861)  ;  Monckton's  patent  (1862);  Gaudin's 

process  (1869) 263 

Kagenbusch's  process  (1872)  ;  Berthaut's  proposition  (1879)  ;  Griitzel's 

process  (1883)  ;  The  apparatus  used,  illustrated  and  described          .  264 
Works  erected  near  Bremen  for  carrying  out  GratzePs  process  ;  The 

uselessness  of  Gratzel's  patent  claims  maintained  by  Prof.  Fischer  .  266 
Abandonment  of  the  Gratzel  process  by  the  works  at  Hemelingen ; 

Kleiner's  process  (1886) 267 

Plants  for  working  Kleiner's  process  put  up  in  England;  Acquirement 

of  the  patents  by  the  Aluminium  Syndicate,  Limited,  of  London  ; 

The  rationale  of  the  process 268 

Purity  of  the  metal  produced  by  Kleiner's  process;  Lossier's  method  271 

Omholt's  furnace 272 

Henderson's  process  (1887)  ;  Bernard  Bros.'  process  (1887)         .         .  273 

Details  of  the  apparatus  and  bath  used  in  Bernard  Bros.'  process          .  274 
Power  required            .         .         .         .         .         .         .         .         .         .276 

Quality  of  metal ;  Reactions  in  the  process 277 

Messrs.  Bernard's  exhibit  at  the  Paris  Exposition;  Feldman's  method 

(1887) 278 

Warren's  experiments  (1887)  .         .         .         .         .         .         .279 

Bognski's  patent ;  Grabau's  apparatus  ;  Rogers's  patent  (1887)            .  280 
The  principle  made  use  of  in   Rogers's  process ;   Experiments  with  a 

small  experimental  plant,  1888 281 

Dr.  Hampe  on  the  electrolysis  of  cryolite ;  Dr.  O.  Schmidt's  experi- 
ence          283 

Dr.  Hampe' s  reply  to  several  communications 284 

Winkler's  patent         . 287 

Faure's  proposition;  Hall's  process  (1889);   Formation  of  the  Pitts- 
burgh Reduction  Company  ;  Claims  made  by  Mr.  Hall  in  his  patents  288 
Description  of  the  plant  erected  in  Pittsburgh     .....  290 

Features  of  Mr.  Hall's  process 291 

Quality  of  the  metal  produced  ;  Efficiency  of  the  process     .         .         .  292 

Probable  cost  of  aluminium  by  Hall's  process;  Cowles  Bros.'  process  .  293 
Prof.   Chas.   F.   Mabery's  and  Dr.  T.  Sterry  Hunt's  descriptions  of 

Cowles  Bros.'  process      .........  294 

Shapes  of  furnaces  used  by  the  Cowles  Bros.'  ;  Retort  patented  by 

Chas.  S.  Bradley  and  Francis  B.  Crocker,  of  New  York          .         .  296 
Furnace  devised  by  Mr.  A.  H.  Cowles  ;   W.  P.  Thompson's  complete 

description  of  the  Cowles  process 297 


XXIV  CONTENTS. 

PAGE 

Illustrative  description  of  the  furnace  ;  Mode  of  operating  the  furnace  .  298 
The  Cowles  Syndicate  Company  of  England,  and  its  plant  at  Milton  .  303 
Standard  grades  of  bronze  produced  by  the  Cowles  Company  ;  Pro- 
ducts of  the  Cowles.  furnace;  Analyses  of  10  per  cent,  bronze; 

Analysis  of  ferro- aluminium    ........     304 

Analysis  of  slag  formed  when  producing  bronze  .....     305 

Reactions  in  Cowles'  process ;  Views  of  Prof.  Mabery,  Dr.  Hunt  and 

Dr.  Kosman 306 

Dr.  Hampe's  conclusions  ;  Useful  effect  of  the  current  .  .  .  307 
Mr.  H.  T.  Dagger's  paper  on  the  Cowles  process  in  England;  Menge's 

patent;  Farmer's  patent         ........     308 

The  Heroult  process  (1887)  ;  Specification  of  the  English  patent  .  309 
Description  of  the  plant  erected  by  the  Societ6  Metallurgique  Suisse  for 

working  the  Heroult  process .310 

The  furnace  or  crucible,  illustrated  and  described         .         .         .         .311 

The  mode  of  operation        .         .         .         .         ..         .         .         .312 

Percentage  of  useful  effect  derived  from  the  current ;  Proof  that  the 

process  is  not  essentially  electrolytic         .         .         .         .         .         .314 

Rapid  extension  of  the  Heroult  process ;  Location  of  plants  in  Europe 

and  in  the  United  States 315 

CHAPTER  XII. 

REDUCTION   OF   ALUMINIUM   COMPOUNDS  BY   OTHER   MEANS   THAN 
SODIUM   OR   ELECTRICITY. 

Reduction  by  carbon  without  the  presence  of  other  metals ;  Article  on 
this  subject  by  M.  Chapelle 316 

Statement  of  G.  W.  Reinar ;  Claims  of  an  aluminium  company  in 
Kentucky 317 

O.  M.  Thowless'  proposition ;  Messrs.  Pearson,  Liddon,  and  Pratt's 
patent;  Reduction  by  carbon  and  carbon  dioxide;  J.  Morris'  claims  318 

Reduction  by  hydrogen  ;  Process  of  F.  W.  Gerhard   .          .         .          .319 

Reduction  by  carburetted  hydrogen ;  Process  of  Mr.  A.  L.  Fleury,  of 
Boston;  Statement  by  Petitjean 320 

Reduction  by  cyanogen  ;  Knowles'  patent ;  Corbelli's  method     .         .     321 

Deville's  comments ;  Experiments  of  Lowthian  Bell ;  Reduction  by 
double  reaction  ;  M.  Comenge's  mode  of  producing  aluminium  sul- 
phide;  The  reactions  involved  ;  Mr.  Niewerth's  process  .  .  322 

Construction  of  a  furnace  used  in  Niewerth's  process;  Mode  of  opera- 
ting the  furnace 323 

Messrs.  Pearson,  Turner,  and  Andrews'  claim ;  Reduction  in  presence 
of,  or  by,  copper;  Messrs.  Calvert  and  Johnson's  experiments  .  324 

Mr.  Evrard's  method  of  making  aluminium  bronze  ;  Benzon's  patent       325 


CONTENTS.  XXV 

PAGE 

G.  A.  Faurie's  method  of  obtaining  aluminium  bronze  ;  Bolley's  and 
List's  examination  of  Benson's  process;  Experiment  by  J.  W. 
Richards  and  Dr.  Lisle 326 

Dr.  W.  Hampe's  test  of  this  subject  and  his  conclusions;  M.  Co- 
menge's  claim  ;  Reichel's  statement  ......  327 

Andrew  Mann's  patent;  L.  Q.  Brin's  process  of  producing  aluminium 
bronze  ;  Reduction  by,  or  in  presence  of,  iron  ;  M.  Comenge's  claim  ; 
F.  Lauterborn's  and  Reichel's  statements  .  .  .  .  .328 

Niewerth's  process  ;   W.  P.  Thompson's  patent  .         .         .         .     329 

Calvert  and  Johnson's  experiments  on  the  reduction  of  aluminium  with 
iron 330 

Mr.  Chenot's  experiments  .         .         .         .         .         .         .         .         .331 

Faraday  and  Stodart's  investigation  on  the  preparation  of  iron-alumin- 
ium alloys ;  Bombay  "  wootz"  steel 332 

Reduction  of  aluminium  in  small  quantities  in  the  blast  furnace ;  Alu- 
minium in  pig-iron;  Schafhautl's,  Lohage's,  Corbin's,  and  Blair's 
statements 333 

G.  H.  Billings'  experiment  on  reducing  alumina  in  contact  with  iron  ; 
E.  Cleaver's  patent  specification 334 

Mode  of  producing  ferro- aluminium  in  Sweden;  Brin  Bros.'  method; 
Similar  claim  made  by  an  aluminium  company  in  Kentucky  .  .  335 

W.  A.  Baldwin's  patents,  owned  by  the  Aluminium  Process  Company, 
of  Washington,  D.  C.  ;  Aluminium-ferro-silicon  manufactured  by  the 
Williams  Aluminium  Company,  of  New  York  City  .  .  .  336 

Reduction  by,  or  in  the  presence  of,  zinc  ;  Observations  by  M.  Bek6toff' 
and  M.  Dullo  ;  M.  N.  Basset's  patent 337 

Mr.  Wedding's  remarks  on  Basset's  process  ;  Experiment  by  J.  Wr. 
Richards  on  the  reduction  of  cryolite  by  zinc ;  Mr.  Fred  J.  Sey- 
mour's  patent  ..........  339 

Description  of  the  plant  of  the  American  Aluminium  Company  of  De- 
troit, working  Dr.  Smith's  patents  .  .  .  .  .  .  .  340 

Patent  of  F.  Lauterborn;  J.  Clark's  patents 341 

Practicability  of  the  distillation  of  zinc  from  an  aluminium-zinc  alloy ; 
Reduction  by  lead  ;  Invention  of  Mr.  A.  E.  Wilde  ....  342 

Reduction  by  manganese  ;  Claims  of  Walter  Weldon  ;  Experiment  of 
Dr.  Greene,  of  Philadelphia;  Reduction  by  magnesium  ;  R.  Gratzel's 
patent;  Roussin's  statement 343 

Patent  of  Count  R.  de  Montgelas,  of  Philadelphia ;  Reduction  by  anti- 
mony ;  F.  Lauterborn's  process 344 

Reduction  by  tin  ;  Statements  by  J.  S.  Howard  and  F.  M.  Hill  in  their 
patent  specifications  ;  Experiment  by  J.  W.  Richards  ;  Reduction  by 
phosphorus  ;  L.  Grabau's  patent 345 

Reduction  by  silicon  ;  General  claims  made  by  M.  Wanner          .         .     346 


XXVI  CONTENTS. 

CHAPTER  XIII. 

WORKING  IN   ALUMINIUM. 

PAGE 

Melting  aluminium  ;  Deville's  instructions  .         .         .         .         .347 

Biederman's  directions  ;  Crucibles  for  melting  aluminium     .         .         .     348 
Protection  of  the  hearth  of  a  reverberatory  furnace  used  for  melting  alu- 
minium ;  Casting  aluminium ;  Deville's  instructions  .         .         .     349 
Peculiarity  of  molten  aluminium  ;  Manner  of  obtaining  sharp  castings  ; 

Dr.  C.  C.  Carroll's  method  of  casting  in  closed  moulds     .         .         .     350 
Purification  of  aluminium;  Freeing  from  slag ;  Deville  on  this  subject     351 

Freeing  from  impurities;  Deville's  instructions 352 

Removal  of  zinc  from  aluminium  by  distillation;    Cupellation  of  alu- 
minium with  lead ;  G.  Buchner's  treatment  of  commercial  aluminium 
to  eliminate  silicon  ;  Experiments  to  test  this  point  .         .         .     353 

Prof.  Mallet's  process  of  obtaining  pure,  from  commercial  aluminium    .     354 
Annealing;  Hardening;  Rolling         .......     355 

Thin  leaf  of  aluminium  first  made,  in  1859,  by  M.  Degousse  ;  Drawing ; 
Ductility  of  aluminium;  Manner  of  drawing  aluminium  tubes ;  Stamp- 
ing and  spinning 356 

Grinding,  polishing,  and  burnishing ;  Biederman's  remarks  on  polishing ; 

Mr.  J.  Richards'  experiments  in  buffing  ;   Engraving        .         .          .     357 
Mat ;   Soldering  of  aluminium  ;  Deville's  views  ;  Hulot's  process  ;  Mou- 
rey's  solders ;  Mourey's  improved  solders ;  Directions  for  preparing 

them 359 

Operation  of  soldering 360 

Solders  and  flux  recommended  by  Col.  Frishmuth  and  by  Schlosser     .     361 
M.  Bourbouze's  method  of  soldering  aluminium;  O.  M.  Thowless's 
patent  solder  and  method  of  applying  it  ......     362 

J.  S.  Sellon's  method;  Coating  metals  with  aluminium;  The  different 

methods  of  procedure 363 

Electrolytic  deposition  of  aluminium,  Veneering  with  aluminium  ;  De- 
ville's account  of  M.  Sevrard's  success,  in  1854  ;  Dr.  Clemens  Winck- 
ler  on  this  subject    ..........     364 

Dr.  G.  Gehring's  method  of  aluminizing ;   Analogous  results  obtained 

by  Brin  Bros. 365 

Plating  on  aluminium  ;  Gilding  and  silvering  ;  Coppering  of  aluminium  ; 
Gilding  aluminium  without  the  use  of  a  battery ;  Veneering  of  alu- 
minium with  other  metals         .         .         .         .         .         .         .         .366 

Morin's  description  of  veneering  with  silver  ;  Uses  of  aluminium  ;  The 
place  assigned  to  aluminium  by  Deville ;  Aluminium  as  a  substitute 
for  silver  ;  Future  wide  applications  of  aluminium    .         .         .         .367 

The  first  article  of  aluminium  ;  Napoleon  III.  interested  in  aluminium  ; 
Military  uses  of  aluminium 368 


CONTENTS.  XXV11 

PAGE 

Superiority  of  aluminium  for  culinary  articles  and  other  purposes  .  369 

Aluminium  for  coinage  ;  Its  use  in  surgery 370 

For  mountings  of  opera-glasses,  etc. ;  Sextant  made  for  Capt.  Gordon 

by  Loiseau,  of  Paris  .  .  .  .  .  .  •  •  .371 

Aluminium  for  aerial  vessels,  torpedo  boats,  etc 372 

Aluminium  for  dental  plates,  etc 373 

Dr.  Fowler's  patent ;  Use  of  aluminium  for  battery  purposes  .  .  374 
For  balances  and  weights  ;  Aluminium  beams  for  balances  made  by 

Sartorius,  of  Gbttingen  ;  Various  uses  of  aluminium  .         .         .375 

CHAPTER  XIY. 

ALLOYS   OP   ALUMINIUM. 

The  practical  manufacture  of  aluminium  alloys  .  .  .  .  .376 
Group  of  useful  alloys;  Reason  why  the  color  of  aluminium  is  not 

radically  altered  by  the  foreign  metal 377 

Explanation  of  the  hardening  and  strengthening  effect  on  aluminium 

by  the  addition  of  a  small  quantity  of  copper  or  silver      .         .         .378 
Effect  of  aluminium  on  metals  alloyed  with  a  small  quantity  of  it ;    Alu- 
minium and  nickel ;  Tissier's  remarks  on  this  subject       .         .         .379 
Michel's  method ;  Aluminium-nickel-copper  alloys  ;  Formulas    .         .     380 
Formulas  of  alloys  resembling  silver;    Prof.   Kirkaldy's  tests  of  Mr. 

James  Webster's  compositions  ;  Formulas  of  these  alloys         .         .     381 
"  Lechesne"  and  its  composition          .......     383 

Cowles  Bros.'  "  Aluminium- Silver"  and  "  Hercules  Metal"        .         .     384 
Aluminium  and  silver  ;  Beneficial  effects  of  silver  on  alumininm  .         .     385 
Dr.  Carroll's  alloy  for  dental  plates  ;  Tiers  Argent ;  Hirzel's  alloys     .     386 
Aluminium  and  gold  ;  Prof.  W.  Chandler  Roberts- Austin  on  the  influ- 
ence of  aluminium  on  gold;    "  Nurnberg  gold";   Aluminium  and 
platinum          .         .         .         .         .         .         .         .          .         .          .387 

Aluminium  and  tin  ;  Alloy  for  the  interior  parts  of  optical  instruments     388 
Influence  of  aluminium  on  tin;  Tissier  Bros.'  statement;  Curious  pro- 
perty of  an  alloy  prepared  by  Mr.  Joseph  Richards          .         .         .389 
Aluminium  and  zinc  ;  Effect  of  zinc  in  small  proportion  on  aluminium  ; 
Deville  on  the  presence  of  zinc  in  aluminium  .....     390 

Aluminium-zinc-copper  alloys;   "  Aluminium  brasses;"  Mode  of  pro- 
ducing them  and  their  properties  ;  Julius  Bauer's  patent  .         .391 
Alloy  patented  by  M.  G.  Farmer,  of  Salem,  Mass.  ;   Series  of  tests 

made  in  1886,  at  the  works  of  Cowles  Bros 392 

Tests  by  the  Aluminium  und  Magnesium  Fabrik,  of  Bremen  ;  Test  of 
aluminium  brasses  by  Prof.  Tetmayer,  of  Zurich  ;  aluminium  and 

cadmium         .  393 

Aluminium  and  mercury ;    Experiments   by  Deville,  Wollaston  and 
Richards;  Investigations  by  Caillet  and  Joule          .         .         .         .394 


XXV111  CONTENTS. 

PAGE 

Gmelin's  statement;  Results  obtained  by  J.  B.  Bailie  and  C.  Fery  .  395 
Properties  of  aluminium  amalgam  .  .  .  .  .  .  .396 

Aluminium  and  lead 397 

Aluminium  and  antimony  ;  Aluminium  and  bismuth  ;  Aluminium  and 

silicon 398 

Effect  of  silicon  on  aluminium  ;  Aluminium  and  magnesium  .  .  400 

Aluminium  and  chromium ;  Aluminium  and  manganese  .  .  .  401 

Aluminium  and  titanium  ;  Aluminium  and  tungsten  ....  402 
Aluminium  and  molybdenum ;  Aluminium  and  gallium  ;  Aluminium 

and  calcium    .         .         .          .         ...          .         .          .          .         .  403 

Aluminium  and  sodium ;  Aluminium  and  boron ;  Aluminium  and 

arsenic.            .         .         .         .         .         .         .         .         .         .         •  404 

Aluminium  and  selenium  ;  Aluminium  and  tellurium  ;  Aluminium  and 

phosphorus  ;  Aluminium  and  carbon         ......  405 

CHAPTER  XV. 

ALUMINIUM-COPPER   ALLOYS. 

Arrangement  of  these  alloys  in  two  groups  .....     406 

Alloys  of  the  first  class;  Effect  of  copper  on  aluminium;  Properties 
and  color  of  alloys  with  over  30  per  cent,  of  copper  .  .  .  407 

Alloys  of  the  second  class ;  Efficiency  of  aluminium  in  improving  the 
qualities  of  copper ;  "Aluminium-bronze;"  Dr.  Percy,  the  first  to 
draw  attention  to  these  alloys  .  .  .  .  .  .  .  408 

Former  mode  of  making  aluminium-bronze;  Prices  in  1864,  quoted  by 
Morin;  Prices  in  1879;  Reduction  in  price  in  1885,  by  Cowles 
Bros 409 

Present  prices  ;  The  low  figure  at  which  aluminium-bronze  is  claimed 
to  be  produced  by  the  Heroult  process ;  Composition  and  nature  of 
the  bronzes;  Formulas 410 

Morin' s  argument  to  prove  that  these  alloys  are  true  chemical  combina- 
tions   411 

Argument  why  aluminium  forms  valuable  bronzes        .         .         .         .412 

Weak  point  in  the  argument        .          .         .         .         .         .         .          .413 

Reasons  why  bronze  made  by  diluting  bronze  with  copper  will  be  prac- 
tically as  good  as  the  one  made  directly  from  the  metals  .  .  .414 

Preparing  the  bronzes ;  Impurities  in  copper  which  effect  the  quality 
of  the  bronze  ;  Quality  of  the  aluminium  ;  Directions  for  preparing 
the  bronzes  by  the  "Magnesium  und  Aluminium  Fabrik"  of  Heme- 
lingen  .  .  .  .  .  .  .  .  .  .  .  .415 

Remelting  of  the  bronze  ;  Operation  of  diluting  a  high  per  cent,  bronze 
to  a  lower  one  .  .  .  .  .  .  .  .  .  .416 

Fusibility;   Casting;  Best  crucible,  for  this  purpose      .         .         .          .417 


CONTENTS.  XXIX 

PAGE 

Moulds  for  casting;  Thomas  D.  West  on  "Casting  aluminium  and 
other  strong  metals"  .  .  .  .  .  .  .  .  .418 

Shrinkage  of  aluminium  bronze ;  Color       .         .         .          .         .          .421 

Specific  gravity ;  Table  of  specific  gravities ;  Hardness ;  Influence  of 
•working  on  the  metal ;  Determinations  made  on  Cowles  Bros.' 
bronzes  at  the  Washington  Navy  Yard  .  .  .  .  .  .422 

Transverse  strength ;  Compressive  strength  ;  Results  obtained  by  Mr. 
Anderson  in  the  Royal  Gun  Foundry  at  Woolwich  ;  Tests  made  on 
Cowles'  bronze  at  the  Watertown  Arsenal 423 

Tensile  strength ;  Results  obtained  by  Lechatelier,  1858;  Determina- 
tions by  Deville  ;  Experiments  made  in  1861 424 

Results  obtained  by  Anderson  at  the  Woolwich  Arsenal ;  Official  tests 
of  the  Cowles'  bronzes  at  the  Watertown  Arsenal  and  at  the  Wash- 
ington Navy  Yard  .  .  .  .  .  .  .  .  .425 

Diagram  showing  tenacity  of  bronzes;  Test  of  Cowles'  bronzes  of 
"  A3"  grade  by  Prof.  Un win 426 

Test  of  Cowles'  B  and  C  grades  by  Mr.  Edw.  D.  Self,  at  the  Stevens 
Institute,  Hoboken,  N.  J.  ;  Tests  of  bronzes  made  at  Neuhausen  by 
the  Heroult  process ;  Results  obtained  by  Prof.  Tetmayer  .  .  427 

Diagram  showing  the  variation  of  tensile  strength  and  elongation  of 
aluminium  bronzes ;  Tests  of  the  effect  of  temperature  on  the 
strength  of  aluminium  bronzes  ;  Annealing  and  hardening  .  .428 

Working ;  Proper  temperature  for  working  the  bronzes ;  Effect  of 
cold  working 429 

Rolling,  drawing,  and  forging  the  bronzes ;  Spinning,  stamping,  press- 
ing, working  with  the  file,  etc.  .......  430 

Anti-friction  qualities ;  Morin's  opinion;  Cowles  Bros.'  recommenda- 
tion; Mr.  Joseph  Richards' s  experiment 431 

Conductivity  for  heat  and  electricity  ;  Resistance  to  corrosion       .         .     432 

Non-oxidability  of  aluminium  bronze  when  heated  in  the  air         .         .     433 

Effect  of  the  weather  on  aluminium  bronze  ;  Uses  of  the  aluminium 
bronzes  ............  434 

The  merits  of  aluminium  bronze  as  a  metal  for  casting  heavy  guns, 
urged  by  Mr.  A.  H.  Cowles 435 

Aluminium  bronze  as  material  for  propeller  blades       ....     436 

Brazing;    Solder  for  brazing;    Soldering;    Deville  on  this   subject; 
Directions  by  Schlosser  for  preparing  solder ;  Formulas  of  solders 
recommended  by  the  Cowles  Co.      .         .         .         .         .         .         .437 

Silicon-aluminium  bronze;  Phosphor-aluminium  bronze;  Patents  of 
Thos.  Shaw,  of  Newark,  N.  J.  438 


XXX  CONTENTS. 

CHAPTER   XYI. 

ALUMINIUM-IRON   ALLOYS. 

PAGE 

Useful  alloys  of  this  class  .         .         .         .         .         .         .         .         .438 

Influence  of  iron  in  small  quantities  on  the  properties  of  aluminium     .     439 
Ferro-aluminium ;  Composition  of  the  Cowles  Company's  ferro-alu- 
minium  ;  Method  of  making  ferro-aluminium ;  Properties  of  these 

alloys 440 

Different  grades  of  ferro- aluminium ;  Absorption  of  aluminium  by  iron 

and  steel  in  the  process  of  their  manufacture  .  .  .  .  .441 
Effect  of  aluminium  on  steel ;  Faraday's  experiments  .  .  .  442 
Experiments  at  Faustman  &  Ostberg's  Mitis  Foundry  at  Carlsvick, 

Sweden,  1885 443 

Results  obtained  by  the  addition  of  aluminium  to  steel;  Explanation  of 

its  effect 444 

Effect  of  aluminium  on  the  welding  of  steel ;  Poor  results  obtained  by 

adding  ferro-aluminium  to  high-carbon  steels 445 

Summary  of  Mr.  Spencer's  experience         ......     446 

Steel-aluminium ;  Best  time  to  add  the  aluminium ;  Effect  of  alu- 
minium on  wrought-iron ;  Discovery  by  Mr.  Wittenstroem,  of 
Stockholm,1  and  Mr.  L.  Nobel,  of  St.  Petersburg  .  .  .  .447 

"Mitis"  castings 448 

Details  of  the  production  of  mitis  castings  ;  Raw  material  .         .         .     449 
Analyses  of  mitis  metal  by  Mr.  Edward  Riley ;  Method  of  treatment     450 
Devices  used  in  connection  with  the  process ;  Nobel's  furnace  for  burn- 
ing naphtha  or  crude  petroleum  ;  Moulding  material         .         .         .451 
Properties   of  mitis   castings ;    Experiments   at  the   Bethlehem   Iron 

Works;  Rationale  of  the  process  ;  Mr.  Ostberg's  explanation  .     452 

Failure  of  Mr.  R.  W.  Davenport  and  Mr.  A.  A.  Blair  to  find  any  alu- 
minium in  mitis  castings  ;  Admission  of  Mr.  Ostberg ;  Explanation 
by  R.  W.  Davenport ;  Reasons  for  the  non-tenability  of  this  ex- 
planation ...........  453 

Explanation  of  the  increased  fluidity  of  the  iron 454 

Causes  of  blow-holes  in  wrought-iron  castings 455 

Causes  of  the  comparative  freedom  of  mitis  castings  from  blow-holes ; 
Mr.  Howe's  suggestion   .........     457 

Summary  of  arguments  presented  ;  Influence  of  aluminium  in  puddling 

iron 458 

Influence  of  aluminium  on  cast-iron 459 

Method  of  adding  ferro  aluminium 460 

Investigation  of  this  subject  by  Mr.  W.  J.  Keep  with  the  co-opera- 
tion of  Prof.  C.  F.  Mabery  and  L.  D.  Vorce           .         .         .         .461 
Solidity  of  castings  ;  Does  the  aluminium  remain  in  the  iron  ?  Tests 
to  determine  this  question •         .462 


CONTENTS.  XXXI 

PAGE 

Transverse  strength  ;  Table  giving  the  percentage  increase  in  strength 
by  the  addition  of  aluminium .  463 

Elasticity ;  Percentage  increase  in  deflection  ;  Tests  to  distinguish  the 
effect  due  to  the  silicon  added  .......  464 

Effect  on  the  grain  ;  Activity  of  aluminium  in  changing  combined  into 
graphitic  carbon 465 

Fluidity  of  the  iron ;  Shrinkage  ;  Table  showing  the  reduction  in  the 
shrinkage  ...........  466 

Hardness ;  Practical  benefit  to  poor  iron  gained  by  adding  ferro- alu- 
minium '...........  467 

Practical  results  ;  The  rationale  of  the  action  of  aluminium  on  cast- 
iron  468 

CHAPTER  XYIL 

ANALYSIS   OF   ALUMINIUM   AND   ALUMINIUM   ALLOYS. 

Elements    commercial    aluminium    may  contain ;    Method   of   attack 

generally  preferred 469 

Qualitative  tests  ;  Specific  gravity  as  a  test  .  .  .  .  .470 
Test  proposed  by  Fr.  Schulze  ;  Determination  of  silicon ;  Deville's 

methods  ...........     471 

Observation  by  Prof.  Rammelsberg    .         .         .         .         .         .         .472 

Determination  of  iron  (and  aluminium)  ;  Deville's  method          .         .473 
H.  Rose's  method        ......  ...     474 

Determination  of  lead ;  Determination  of  copper ;  Determination  of 

zinc        ............     476 

Determination  of  tin ;  Determination  of  silver ;  Determination  of 

sodium 477 

Determination  of  chlorine ;  Determination  of  carbon  ;  Determination 

of  fluorine ;  Procedure  recommended  by  Deville  ;  Analysis  of  ferro- 

aluminiums 478 

Mr.  H.  N.  Yates's  experience  ;  Chancel's  separation  .  .  .479 

Mr.  R.  T.  Thompson's  method 480 

Method  giving  the  author  satisfactory  results  ;  Method  recommended 

by  A.  A.  Blair 481 

Electrolytic  method 482 

Method  of  procedure  given  by  Dr.  Classen  ;  Electrolytic  method  of 

Prof.  Edgar  T.  Smith 483 

Analysis  of  aluminium  bronze    ........     484 

General  remarks  ..........  486 

INDEX       .-  .  ...     489 


ERRATA. 

Page  54,  analysis  7  :  Instead  of  "  silicon  0.80,  iron  4.40,  read  "  silicon  4.40,  iron 
0.80." 
Page  61,  ninth  line  from  foot :  Instead  of  Picktet,  read  Pictet. 


TEMPERATURES. 

Unless  otherwise  stated,  all  temperatures  are  given  in  Centigrade  degrees. 


ALUMINIUM. 


CHAPTER  I. 

HISTORY  OF  ALUMINIUM. 

ABOUT  1760,  Morveau  called  the  substance  obtained  by  cal- 
cining alum-alumina.  When,  afterwards,  Lavoisier  first  sug- 
gested the  existence  of  metallic  bases  of  the  earths  and  alkalies, 
and  alumina  was  suspected  of  being  the  oxide  of  a  metal,  the 
metal  was  called  aluminium.  This,  long  before  it  was  isolated. 

The  first  researches  in  the  preparation  of  aluminium  date  back 
to  1807.  Davy  tried,  but  in  vain,  to  decompose  alumina  by  an 
electric  current,  or  to  reduce  it  by  vapor  of  potassium.  Oer- 
stedt,  in  1824,  believed  he  had  isolated  aluminium.  He  decom- 
posed anhydrous  aluminium  chloride  by  potassium  amalgam,  and 
obtained,  along  with  some  potassium  chloride,  an  amalgam  which 
when  decomposed  by  heat  furnished  him  a  metal  resembling  tin. 
It  is  probable  that  he  employed  either  some  moist  aluminium 
chloride  or  potassium  amalgam  which  contained  caustic  potash, 
for  it  is  only  when  wetted  with  a  solution  of  caustic  potash  that 
aluminium  alloys  with  mercury ;  for  when  Wohler,  later,  wished 
to  prepare  aluminium  by  this  method,  he  found  it  impossible  to 
obtain  an  aluminium  amalgam  when  he  employed  materials  pure 
and  dry.  Nevertheless,  the  method  of  Oerstedt  marks  an  epoch 
in  the  history  of  aluminium,  for,  in  1827,  Wohler  isolated  it 
by  decomposing  aluminium  chloride  by  potassium.  The  metal 
first  isolated  by  Wohler  was  a  gray  powder,  taking  under 
the  polisher  the  brilliancy  of  tin.  It  was  very  easily  changed, 
because  of  its  extreme  division,  and  also  because  it  was  mixed 

2 


18  ALUMINIUM. 

with  the  potassium  or  aluminium  chloride  used  in  excess.  At  that 
time  no  further  use  was  made  of  these  facts.  Later,  in  1845,  011 
making  vapor  of  aluminium  chloride  pass  over  potassium  placed 
in  platinum  boats,  Wohler  obtained  the  metal  in  small,  malleable 
globules  of  metallic  appearance,  from  which  he  was  able  to  deter- 
mine the  principal  properties  of  aluminium.  But  the  metal  thus 
obtained  was  scarcely  as  fusible  as  cast  iron,  without  doubt 
because  of  the  platinum  with  which  it  had  alloyed  during  its 
preparation.  In  addition  to  this,  it  decomposed  water  at  100°, 
from  which  we  suppose  that  it  was  still  impregnated  with  potas- 
sium or  aluminium  chloride.  It  is  to  H.  St.  Claire  Deville  that 
the  honor  belongs  of  having,  in  1854,  isolated  aluminium  in  a 
state  of  almost  perfect  purity,  determining  its  true  properties. 

Thus,  while  aluminium  had  been  isolated  in  1827,  for  eighteen 
years  its  properties  en  masse  were  unknown,  and  it  was  only  at 
the  end  of  twenty-seven  years  after  its  discovery  that  the  true 
properties  of  the  pure  metal  were  established  by  Deville.  The 
second  birth  of  aluminium,  the  time  at  which  it  stepped  from  the 
rank  of  a  curiosity  into  the  number  of  the  useful  metals,  dates 
from  the  labors  of  Deville  in  1854.  If  Wohler  was  the  dis- 
coverer of  aluminium,  Deville  was  the  founder  of  the  aluminium 
industry. 

In  commencing  researches  on  aluminium,  Deville,  while  he 
applied  the  method  of  Wohler,  was  ignorant  of  the  latter' s  results 
of  1845.  Besides,  he  was  not  seeking  to  produce  aluminium 
that  he  might  turn  its  valuable  properties  to  practical  account, 
but  that  it  might  serve  for  the  production  of  aluminium  prot- 
oxide (A1O),  which  he  believed  could  exist  as  well  as  ferrous 
oxide  (FeO).  The  aluminium  he  wished  to  prepare  would,  he 
thought,  by  its  further  reaction  on  aluminium  chloride,  form  alu- 
minium proto-chloride  (A1C12)  from  which  he  might  derive  the 
protoxide  and  the  other  proto-salts.  But  on  passing  vapor  of  alu- 
minium chloride  over  the  metallic  powder  formed  by  reduction 
by  potassium,  this  proto-chloride  was  not  thus  produced ;  he 
obtained,  inclosed  in  a  mass  of  aluminium-potassium  chloride 
(APC16.2KC1),  fine  globules  of  a  brilliant  substance,  ductile,  malle- 
able, and  very  light,  capable  of  being  melted  in  a  muffle  without 
oxidizing,  attacked  by  nitric  acid  with  difficulty,  but  dissolved 


HISTORY   OF   ALUMINIUM.  19 

easily  by  hydrochloric  acid  or  caustic  potash  with  evolution  of 
hydrogen. 

Deville  troubled  himself  no  more  about  the  proto-salts  of 
aluminium,  but,  recognizing  the  importance  of  his  discovery, 
turned  his  attention  to  preparing  the  metal.  He  was  at  this 
time  Professor  of  Chemistry  in  the  Ecole  Normale,  Paris,  his 
salary  was  but  3000  francs,  his  estate  was  small,  and  he  was 
practically  without  the  means  of  doing  anything  further. 

On  Monday,  February  6,  1854,  Deville  read  at  the  seance  of 
the  Academy  a  short  paper  entitled  "  Aluminium  and  its  Chemi- 
cal Combinations,"  in  wrhich  he  explained  the  results  of  this 
experiment  as  showing  the  true  properties  of  aluminium  and  also 
furnishing  a  method  of  purifying  it,  and  declared  his  intention  oi 
commencing  immediate  search  for  a  process  which  could  be  eco- 
nomically applied  on  a  commercial  scale.  M.  Thenard,  at  the 
close  of  the  communication,  remarked  that  such  experiments 
ought  to  be  actively  pursued,  and  that,  since  they  were  costly,  he 
believed  the  Academy  would  hasten  the  accomplishment  of  the 
work  by  placing  at  Deville's  disposal  the  necessary  funds.  As 
the  outcome  of  this,  the  Academy  appointed  Deville  one  of  a 
committee  to  experiment  on  producing  aluminium,  and  2000 
francs  were  placed  at  his  disposal  for  the  work. 

It  was  on  the  occasion  of  the  reading  of  this  paper  that  M. 
Chenot  addressed  a  note  to  the  Academy  on  the  preparation  of 
aluminium  and  other  earthy  and  alkaline  metals,  in  which  he 
claimed,  in  some  regards,  priority  for  his  inventions.  (See  fur- 
ther under  "  Reduction  by  Carbon.")  This  note  was  reserved 
to  be  examined  by  a  commission  appointed  to  take  notice  of  all 
communications  relative  to  the  production  of  aluminium. 

With  the  funds  thus  placed  at  Deville's  disposal  he  experi- 
mented at  the  ficole  Normale  for  several  months.  As  potassium 
is  very  dangerous  to  handle,  cost  then  900  francs  a  kilo,  and  gives 
comparatively  but  a  small  return  of  aluminium,  Deville,  in  view 
of  the  successful  work  of  Bunsen  on  the  electric  decomposition 
of  magnesium  chloride,  tried  first  the  reduction  of  aluminium 
chloride  by  the  battery.  On  March  20,  1854,  Deville  an- 
nounced to  the  Academy  in  a  letter  to  Dumas  that  he  had  pro- 
duced aluminium  without  alkaline  help,  and  sent  a  leaf  of  the 


20  ALUMINIUM. 

metal  thus  obtained.  At  that  time  Thenard,  Boussingault, 
Pelouze,  Peligot,  and  later,  de-la-Rive,  Regnault  and  other  well- 
known  scientists  shared  the  honor  of  assisting  in  the  laboratory 
experiments.  Deville  sent,  in  the  following  May,  a  mass  of 
five  or  six  grammes  weight  to  Liebig,  making  no  secret  of  the 
fact  that  it  was  reduced  by  the  battery ;  while  Balard,  at  the 
Sorbonne,  and  Fremy,  at  the  Ecole  Polytechnique,  publicly  re- 
peated his  experiments  and  explained  them  in  all  their  details. 
Although  these  experiments  succeeded  quite  well,  yet,  because  of 
the  large  consumption  of  zinc  in  the  battery  used  the  process 
could  evidently  not  be  applied  industrially,  and  Deville  felt 
obliged  to  return  to  the  use  of  the  alkaline  metals. 

Towards  the  middle  of  1854,  Deville  turned  to  sodium,  with- 
out a  knowledge  of  those  properties  which  render  it  so  pref- 
erable to  potassium,  but  solely  because  of  its  smaller  equivalent 
(23  to  that  of  potassium  39)  and  the  greater  cheapness  of  soda 
salts.  He  studied  the  manufacture  of  sodium,  with  the  aid  of 
M.  Debray,  in  his  laboratory  at  the  Ecole  Normale,  and  their 
experiments  were  repeated  at  Rousseau  Bros/  chemical  works  at 
Glaciere,  when  they  were  so  successful  that  Rousseau  Bros,  very 
soon  put  metallic  sodium  on  the  market  at  a  much  reduced 
price.  It  is  said  that  while  metallic  sodium  was  a  chemical 
curiosity  in  1855,  costing  something  like  2000  francs  a  kilo,  its  cost 
in  1859  is  put  down  at  10  francs.  Deville  carried  this  process  to 
such  perfection  that  for  twenty-five  years  it  remained  almost  pre- 
cisely at  the  status  in  which  he  left  it  in  1859.  In  order  to  still 
further  cheapen  aluminium,  Deville  busied  himself  with  the 
economic  production  of  alumina,  which  gave  later  a  lively  im- 
pulse to  the  cryolite  and  bauxite  industries. 

On  August  14,  1854,  Deville  read  a  paper  before  the  Aca- 
demy describing  his  electrolytic  methods  at  length  (s^e  under 
"  Reduction  by  Electricity"),  showing  several  small  bars  of  the 
metal  and  also  stating  some  of  the  results  already  achieved  by 
the  use  of  sodium  but  not  going  into  details,  since  he  believed 
that  numerous  analyses  were  necessary  to  confirm  these  results — 
which  he  was  unable  to  have  made  with  the  funds  at  his  disposal. 
He  also  stated  that  the  desire  to  show,  in  connection  with  his 
assertions,  interesting  masses  of  the  metal,  alone  prevented  the 


HISTORY   OF   ALUMINIUM.  21 

earlier  publication  of  the  methods  used.  Several  days  before 
this,  Bunsen  published  in  Poggendorff  s  Annalen  a  process  for 
obtaining  aluminium  by  the  battery,  which  resembled  Deville's 
method,  but  of  which  the  latter  was  ignorant  when  he  read  his 
paper.  Thus  it  is  evident  that  the  isolation  of  aluminium  by  elec- 
trolysis was  the  simultaneous  invention  of  Deville  and  Bunsen. 

After  reading  this  paper,  Deville  caused  a  medal  of  aluminium 
to  be  struck,  which  he  presented  to  the  Emperor  Napoleon  III. 
The  latter,  looking  forward  to  applying  such  a  light  metal  to  the 
armor  and  helmets  of  the  French  Cuirassiers,  immediately 
authorized  experiments  to  be  continued  at  his  own  expense  on  a 
large  scale.  This  anticipation  ultimately  proved  impracticable, 
but  the  ambition  in  which  it  was  bred  was  caused  for  once  to 
minister  to  the  lasting  benefit  of  mankind.  Deville,  however, 
about  this  time  accepted,  in  addition  to  his  duties  as  professor  at 
the  Ecole  Normale,  a  lectureship  at  the  Sorbonne  (where  he  after- 
wards obtained  a  full  professorship),  and  it  was  not  until  March 
of  the  next  year  that  the  experiments  at  the  cost  of  the  Emperor 
were  begun. 

It  was  about  August,  1854,  that  two  young  chemists,  Chas. 
and  Alex.  Tissier,  at  the  suggestion  of  Deville,  persuaded  M. 
De  Sussex,  director  of  a  chemical  works  at  Javel,  to  let  them  ex- 
periment in  his  laboratory  (of  which  they  had  charge)  on  the 
production  of  sodium. 

Towards  the  commencement  of  1855,  Deville  took  up  the  in- 
dustrial question,  the  Emperor  putting  at  his  disposition  all  the 
funds  necessary  for  the  enterprise,  and  in  March  the  investigator 
Avent  to  work  and  installed  himself  at  the  chemical  works  at 
Javel  in  a  large  shed  which  the  director,  M.  De  Sussex,  kindly 
put  at  his  service. 

The  investigations  were  carried  on  here  for  nearly  four  months, 
ending  June  29th,  and  the  process  elaborated  was  an  application 
on  a  large  scale  of  the  experiments  he  had  made  at  the  expense 
of  the  Academy,  which  he  described  in  his  paper  of  August  14, 
1854,  and  by  which  he  had  been  able  to  obtain  a  few  pencils  of 
metal.  In  this  work  such  success  attended  his  efforts  that  on 
June  18,  Deville  presented  to  the  Academy  through  M.  Dumas 
large  bars  of  pure  aluminium,  sodium  and  masses  of  aluminium 


22  ALUMINIUM. 

chloride.  The  members-  and  large  audience  were  loud  in  their 
admiration  and  surprise  at  the  beauty  of  the  metal.  Dumas 
stated  that  the  experiments  at  Javel  had  put  beyond  a  doubt 
the  possibility  of  extracting  aluminium  on  a  large  scale  by  prac- 
tical processes.  Deville's  paper  was  then  read,  describing  all  his 
processes  in  detail,  and  concluding  with  the  following  words : 
"  After  four  months  of  work  on  a  large  scale,  undertaken  with- 
out responsibility  on  my  part,  and,  in  consequence,  with  the  tran- 
quillity and  repose  of  mind  which  are  so  often  wanting  to  the 
investigator ;  without  the  preoccupation  of  expense,  borne  by  his 
Majesty  the  Emperor,  whose  generosity  had  left  me  entire  liberty 
of  action;  encouraged  each  day  by  distinguished  men  of  science, 
— I  hope  to  have  placed  the  aluminium  industry  on  a  firm  basis." 

It  was  the  metal  made  at  this  time  at  Javel  which  was  ex- 
hibited at  the  Paris  Exposition  in  1855.  In  the  Palais  de  Fln- 
dustrie,  among  the  display  from  the  porcelain  works  at  Sevres, 
were  ingots  and  some  manufactured  objects.  The  first  article 
made  of  aluminium  was,  in  compliment  to  the  Emperor,  a  baby- 
rattle  for  the  infant  Prince  Imperial,  for  which  purpose  it  must 
have  served  well  because  of  the  sonorousness  of  the  metal. 

After  terminating  these  experiments,  Deville  continued  work- 
ing at  the  ficole  Normale,  the  Emperor  defraying  his  expenses, 
until  April,  1856.  The  memoir  published  in  the  "  Ann.  de  Chim. 
et  de  Phys.,"  April,  1856,  contains,  besides  the  results  obtained  at 
Javel,  the  improvements  devised  in  the  meantime. 

It  appears  that  when  Deville  first  went  to  Javel,  he  had  for 
assistants  the  Tissier  Brothers,  who  were  charged  by  M.  de  Sus- 
sex to  give  him  all  the  aid  they  could.  Since  the  previous  autumn 
the  Tissiers  had  been  experimenting  on  sodium  furnaces,  and 
now,  in  concert  with  Deville,  they  drew  up  plans  for  furnaces, 
and  aided  in  devising  other  apparatus.  Under  these  circum- 
stances the  furnace  for  the  continuous  manufacture  of  sodium  in 
cylinders  was  devised,  which  the  Tissiers  claim  Deville  strongly 
advised  them  to  make  their  property  by  patenting,  asking  only 
from  them  the  use  of  it  for  his  experiments.  So,  immediately 
after  the  experiments  were  ended,  in  July,  the  Tissiers  patented 
the  furnace  in  question,  and,  leaving  Paris,  took  charge  of  M. 
Chanu's  works  at  Rouen.  On  the  other  hand,  Deville  always 


HISTORY   OF   ALUMINIUM.  23 

reproached  them  for  acting  in  bad  faith.  He  says  that  after 
having  assisted  for  about  two  months  in  setting  up  his  apparatus, 
being  forced  to  leave  the  works  because  of  misunderstandings 
between  them  and  M.  de  Sussex,  they  were  admitted  to  his 
laboratory  at  the  Ecole  Nor  male,  and  initiated  by  him  into  the 
knowledge  of  all  those  processes  which  they  made  use  of  after- 
wards, then  suddenly  left,  taking  drawings  of  furnaces,  details  of 
processes,  etc.,  which  they  not  only  made  free  use  of,  but  even 
patented.  However,  whichever  party  was  in  the  right  (and  those 
who  comprehend  the  character  of  Deville  can  hardly  doubt 
which  was),  the  fact  stands  that  in  July,  1855,  M.  Chanu,  an 
honorable  manufacturer  of  Rouen,  founded  a  works  in  which 
Deville's  processes  were  to  be  applied,  and  intrusted  the  direction 
of  it  to  the  Tissier  Brothers. 

The  history  of  the  works  at  Rouen  is  thus  described  by  the 
Tissiers  in  their  book  on  aluminium,  of  which  we  shall  speak  a 
little  further  on  : — 

"In  July,  1855,  Messrs.  Maletra,  Chanu,  and  Davey,  of 
Rouen,  formed  a  company  to  produce  aluminium,  and  we  were 
intrusted  with  the  organization  and  special  charge  of  the  in- 
dustry. The  commencement  was  beset  with  difficulties,  not  only 
in  producing  but  in  using  the  metal.  It  then  sold  at  $200  per 
kilo,  the  price  being  an  insurmountable  obstacle  to  its  employ- 
ment in  the  arts.  The  small  capital  at  our  disposal  was  not 
enough  to  start  the  industry,  to  pay  general  expenses,  and  the 
losses  occasioned  by  the  many  experiments  necessary.  On  Feb- 
ruary 28,  1856,  the  society  was  dissolved.  In  April  of  the  same 
year,  Mr.  William  Martin,  struck  by  the  results  already  obtained 
and  sanguine  of  greater  success,  united  with  us.  From  that  time 
daily  improvements  confirmed  M.  Martin's  hopes,  and  in  1857 
the  works  at  Amfreville-la-mi-Voie,  near  Rouen,  sold  the  metal 
at  $60  per  kilo  ($2  per  oz.).  The  laboratory  of  this  works  was 
devoted  to  researches  on  everything  concerning  the  production 
and  application  of  aluminium.  M.  Martin  has  our  sincere  grati- 
tude for  the  kindness  with  which  he  so  willingly  encouraged  and 
contributed  to  the  progress  of  the  manufacture  of  this  wonderful 
metal." 

The  process  ultimately  used  at  Amfreville  was  the  reduction  of 


24  ALUMINIUM. 

cryolite  by  sodium,  but  the  enterprise  was  not  a  permanent  suc- 
cess, and  after  running  for  a  few  years  it  was  abandoned  and  the 
works  closed. 

Returning  to  Deville,  we  find  that  after  leaving  Javel  one  of 
the  first  subjects  he  investigated  was  the  use  of  cryolite  for  pro- 
ducing aluminium.  The  researches  made  with  the  aid  of  MM. 
Morin  and  Debray  were  published  in  the  memoir  of  April,  1856, 
and  became  the  basis  of  the  process  carried  out  by  the  Tissiers  at 
Rouen.  Besides  this,  Deville  perfected  many  of  the  details  of  a 
practicable  aluminium  plant,  with  the  result  that  in  the  spring  of 
1856  he  united  with  Messrs.  Debray,  Morin,  and  Rosseau  Bros, 
(the  latter  manufacturers  of  chemicals  at  Glaciere,  in  whose 
works  aluminium  had  been  made  since  the  middle  of  1855)  and 
put  up  new  apparatus  in  the  works  at  Glaciere,  the  company  fur- 
thering the  work  entirely  at  their  own  cost.  This  enterprise 
lasted  for  more  than  a  year,  during  which  a  number  of  processes 
were  tried  and  continued  improvements  made,  so  that  towards 
August  of  the  same  year  aluminium  was  put  on  the  market  in 
Paris  at  300  francs  a  kilo,  being  one-third  what  it  cost  a  year 
previous. 

Finally,  in  April,  1857,  the  little  works  at  Glaciere,  a  suburb 
of  Paris,  in  the  midst  of  gardens  and  houses,  and  turning  into 
the  air  fumes  charged  with  chlorine  and  salts,  was  obliged  by 
reason  of  general  complaints  to  stop  making  aluminium.  The 
plant  was  moved  to  Nanterre,  where  it  remained  for  some  years, 
under  the  direction  of  M.  Paul  Morin,  being  on  a  scale  four 
times  as  large  as  the  actual  demand.  Afterwards  part  of  the 
plant  was  moved  to  the  works  of  H.  Merle  &  Co.",  at  Salindres, 
and  later  on  the  whole  plant,  where  the  manufacture  is  now  car- 
ried on  by  the  firm  of  Pechiney  &  Co.  The  works  at  Nanterre 
were  really  the  only  "aluminium  works"  built  by  Deville,  the 
others  were  plants  installed  at  general  chemical  works,  but  these  at 
Nanterre  were  built  by  the  united  efforts  of  Deville,  his  brothers 
and  parents,  and  a  few  personal  friends.  Among  those  who 
aided  Deville,  especially  in  the  problems  which  the  new  industry 
presented,  he  speaks  warmly  of  Messrs.  d'Eichtal,  Lechatelier, 
and  Jacquemont. 

In  1858  the  Tissiers  wrote  and  published  a  small  work  entitled 


HISTORY   OF   ALUMINIUM.  25 

"  Recherches  sur  1J Aluminium/'  which,  in  view  of  what  Deville 
could  have  written  about  the  subject,  was  a  decided  misrepre- 
sentation of  the  results  which  had  been  thus  far  accomplished. 
Deville  thought  that  the  industry  was  yet  too  young  to  merit  any 
sort  of  publication,  yet  he  naively  writes  in  his  work  "De  V Alu- 
minium/7 in  1859,  "  I  will  sincerely  acknowledge  that  my  writing 
is  a  little  due  to  my  pride,  for  I  decided  to  take  the  pen  to  speak 
of  my  work  only  to  avoid  seeing  it  belittled  and  disfigured  as 
it  has  been  lately  in  the  book  written  by  the  MM.  Tissier." 

Deville  published  his  book  in  September,  1859,  and  he  con- 
cludes it  with  these  words  :  "  I  have  tried  to  show  that  aluminium 
may  become  a  useful  metal  by  studying  with  care  its  physical 
and  chemical  properties,  and  showing  the  actual  state  of  its 
manufacture.  As  to  the  place  which  it  may  occupy  in  our  daily 
life,  that  will  depend  on  the  public's  estimation  of  it  and  its  com- 
mercial price.  The  introduction  of  a  new  metal  into  the  usages 
of  man's  life  is  an  operation  of  extreme  difficulty.  At  first 
aluminium  was  spoken  of  too  highly  in  some  publications,  which 
made  it  out  to  be  a  precious  metal ;  but  later  these  estimates  have 
depreciated  even  to  the  point  of  considering  it  attackable  by  pure 
water.  The  cause  of  this  is  the  desire  which  many  have  to  see 
taken  out  of  common  field-mud  a  metal  superior  to  silver  itself; 
the  opposite  opinion  established  itself  because  of  very  impure 
specimens  of  the  metal  which  were  put  in  circulation.  It  seems 
now  that  the  intermediate  opinion,  that  which  I  have  always 
held  and  which  I  express  in  the  first  lines  of  my  book,  is  be- 
coming more  public  and  will  stop  the  illusions  and  exaggerated 
beliefs  which  can  only  be  prejudicial  to  the  adoption  of  aluminium 
as  a  useful  metal.  Moreover,  the  industry,  established  as  it  now 
is,  can  be  the  cause  of  loss  to  no  one ;  as  for  myself,  I  take  no 
account  of  the  large  part  of  my  estate  which  I  have  devoted,  but 
am  only  too  happy,  if  my  efforts  are  crowned  with  definite  success, 
in  having  made  fruitful  the  work  of  a  man  whom  I  am  pleased 
to  call  my  friend — the  illustrious  Wb'hler." 

Contemporary  with  the  early  labors  of  Deville,  among  the 
numerous  chemists  and  metallurgists  investigating  this  attractive 
field  we  find  Dr.  Percy  in  England,  and  H.  Rose  in  Germany, 


26  ALUMINIUM. 

whose  experiments  on  the  reduction  of  cryolite  by  sodium  were 
quite  successful,  and  are  herein  described  later  on. 

As  early  as  1856  we  find  an  article  in  an  American  magazine* 
showing  that  there  were  already  chemists  in  the  United  States 
spending  time  and  money  on  this  subject.  The  following  is  the 
substance  of  the  article  alluded  to:  "Within  the  last  two  years 
Deville  has  extracted  50  to  60  Ibs.  of  aluminium.  At  the  pre- 
sent time,  M.  Rousseau,  the  successor  of  Deville  in  this  manu- 
facture, produces  aluminium  which  he  sells  at  $100  per  pound. 
No  one  in  the  United  States  has  undertaken  to  make  the  metal 
until  recently  Mons.  Alfred  Monnier,  of  Camden,  N.  J.,  has,  ac- 
cording to  the  statement  of  Prof.  James  C.  Booth  in  the  '  Penn. 
Inquirer/  been  successful  in  making  sodium  by  a  continuous  pro- 
cess, so  as  to  procure  it  in  large  bars,  and  has  made  aluminium 
in  considerable  quantity,  specimens  of  which  he  has  exhibited  to 
the  Franklin  Institute.  Mons.  Monnier  is  desirous  of  forming  a 
company  for  the  manufacture  of  aluminium,  and  is  confident 
that  by  operating  in  a  large  way  he  can  produce  it  at  a  much 
less  cost  than  has  heretofore  been  realized.  We  would  suggest 
the  propriety  of  giving  aid  to  this  manufacturer  at  the  expense  of 
the  government,  for  the  introduction  of  a  new  metal  into  the  arts 
is  a  matter  of  national  importance,  and  no  one  can  yet  realize  the 
various  and  innumerable  uses  to  which  this  new  metal  may  be 
applied.  It  would  be  quite  proper  and  constitutional  for  Con- 
gress to  appropriate  a  sum  of  money  to  be  expended  under  the 
direction  of  the  Secretary  of  the  Treasury  in  the  improvement  of 
this  branch  of  metallurgy,  and  in  testing  the  value  of  the  metal 
for  coinage  and  other  public  use." 

In  the  next  volume  of  the  "  Mining  Magazine"f  there  is  a  long 
article  by  Mr.  W.  J.  Taylor,  containing  nothing  new  in  regard 
to  the  metallurgy  of  aluminium,  but  chiefly  concerned  in  calcu- 
lating theoretically  the  cost  of  the  metal  from  the  raw  materials 
and  labor  required  by  Deville's  processes,  and  concluding  that  it 
is  quite  possible  to  make  it  for  $1.00  per  pound. 

In  1859  the  first  aluminium  works  in  England  were  started  at 

*  Mining  Magazine,.  1856,  vii.  317. 

f  Mining  Magazine,  viii.  167  and  228.     Proc.  Ac.  Nat.  Soi.,  Jan.  1857. 


HISTORY   OF   ALUMINIUM.  27 

Battersea,  near  London.  No  details  are  attainable  respecting  the 
size  of  these  works  or  the  length  of  time  they  were  in  operation. 
They  very  probably  were  merged  into  the  enterprise  started  the 
next  year,  I860,  at  Newcastle-on-Tyne,  by  the  Bell  Bros. — one  of 
whom  was  I.  Lowthian  Bell,  so  prominent  in  connection  with 
the  metallurgy  of  iron.  In  1862  this  company  was  selling  their 
aluminium  at  40  shillings  per  troy  pound,  and  they  continued 
operations  until  1874,  when  the  works  wrere  closed. 

It  was  probably  shortly  after  1874  that  the  large  firm  of  J. 
F.  Wirtz  &  Co.,  Berlin,  made  an  attempt  to  start  an  aluminium 
works.  The  project  drooped  before  it  wras  well  started,  and  it  is 
only  within  the  last  five  years  that  Germany  has  possessed  a 
flourishing  aluminium  industry. 

The  further  we  get  away  from  an  age  the  better  able  are  we  to 
write  the  true  history  of  that  age.  And  so,  as  years  pass  since 
the  labors  of  Wohler,  Deville,  and  Tissier,  we  are  now  able  to  see 
better  the  whole  connected  history  of  the  development  of  this 
art.  Dr.  Clemens  Winckler  gives  us  a  comprehensive  retrospect 
of  the  field  seen  from  the  standpoint  of  1879,  from  which  we 
condense  the  following.*  "The  history  of  the  art  of  working 
in  aluminium  is  a  very  short  one,  so  short  that  the  present  genera- 
tion, with  which  it  is  contemporary,  is  in  danger  of  overlooking  it 
altogether.  The  three  international  exhibitions  which  have  been 
held  in  Paris  since  aluminium  first  began  to  be  made  on  a  com- 
mercial scale  form  so  many  memorials  of  its  career,  giving  as 
they  did  at  almost  equal  intervals  evidence  of  the  progress 
made  in  its  application.  In  1855  we  meet  for  the  first  time  in 
the  Palais  de  ^Industrie  with  a  large  bar  of  the  wonderful  metal, 
docketed  with  the  extravagant  name  of  the  '  silver  from  clay.' 
In  1867  we  meet  with  it  again  worked  up  in  various  forms,  and 
get  a  view  of  the  many  difficulties  which  had  to  be  overcome  in 
producing  it  on  a  large  scale,  purifying  and  moulding  it.  We 
find  it  present  as  sheets,  wire,  foil,  or  worked-up  goods,  polished, 
engraved,  and  soldered,  and  see  for  the  first  time  its  most  import- 
ant alloy — aluminium  bronze.  After  a  lapse  of  almost  another 
dozen  years,  we  see  at  the  Paris  Exhibition  of  1878  the  maturity 

*  Industrie  Blatter,  1879  ;  Sci.  Am.  Suppl.,  Sept.  6,  1879. 


28  ALUMINIUM. 

of  the  industry.  We  have  passed  out  of  the  epoch  in  which  the 
metal  was  worked  up  in  single  specimens,  showing  only  the 
future  capabilities  of  the  metal,  and  we  see  it  accepted  as  a  cur- 
rent manufacture  having  a  regular  supply  and  demand,  and  being 
in  some  regards  commercially  complete.  The  despair  which  has 
been  indulged  in  as  to  the  future  of  the  metal  is  thus  seen  to 
have  been  premature.  The  manufacture  of  aluminium  and  goods 
made  of  it  has  certainly  not  taken  the  extension  at  first  hoped 
for  in  its  behalf;  the  lowest  limit  of  the  cost  of  manufacture  was 
soon  reached,  and  aluminium  remains  as  a  metal  won  by  expensive 
operations  from  the  cheapest  of  raw  materials. 

"  There  are  several  reasons  why  the  metal  is  shown  so  little 
favor  by  mathematical  instrument  makers  and  others.  First  of 
all,  there  is  the  price ;  then  the  methods  of  working  it  are  not 
everywhere  known ;  and  further,  no  one  knows  how  to  cast  it. 
Molten  aluminium  attacks  the  common  earthen  crucible,  reduces 
silicon  from  it,  and  becomes  gray  and  brittle.  This  inconvenience 
is  overcome  by  using  lime  crucibles,  or  by  lining  an  earthen  cru- 
cible with  carbon  or  strongly  burnt  cryolite  clay.  If  any  one 
would  take  up  the  casting  of  aluminium  and  bring  it  into  vogue 
as  a  current  industrial  operation,  there  is  no  doubt  that  the  metal 
would  be  more  freely  used  in  the  finer  branches  of  practical 
mechanics." 

At  the  time  of  Dr.  Winckler's  writing,  the  extraction  of 
aluminium  in  France  was  carried  on  by  Merle  &  Co.,  at  Salindres, 
while  the  Societe  Anonyme  de  1' Aluminium,  at  Nanterre,  worked 
up  the  metal.  Both  firms  were  represented  at  the  Exposition  of 
1878.  The  prices  quoted  then  were  130  francs  a  kilo  for  alumin- 
ium, and  18  francs  for  ten  per  cent,  aluminium  bronze.  From 
1874,  when  Bell  Bros/  works  at  Newcastle-on-Tyne  stopped 
operations,  until  1882,  when  a  new  enterprise  was  started  in 
England  by  Mr.  Webster,  the  French  company  were  the  only 
producers  of  aluminium. 

Regarding  the  prospects  of  the  aluminium  industry  at  this 
period,  we  can  very  appropriately  quote  some  remarks  of  the  late 
Mr.  Walter  Weldon,  F.R.S.,  who  was  a  personal  friend  of  M. 
Pechiuey  (director  of  the  works  at  Salindres),  had  given  great 
attention  to  aluminium,  and  was  considered  as  a  first  authority  on 


HISTORY   OF   ALUMINIUM.  29 

the  subject.  Speaking  in  March  1883,  before  the  London  Section 
of  the  Society  of  Chemical  Industry,  he  stated  that  the  only 
method  then  practised  for  the  manufacture  of  aluminium  was 
Deville's  classical  one ;  that  at  Salindres,  M.  Pechiney  had  im- 
proved and  cheapened  it,  but  that  was  all  the  progress  made  in 
the  industry  in  twenty-five  years.  Continuing,  Mr.  Weldon  out- 
lined the  possible  lines  on  which  improvements  might  be  made  as  : 

1st.  Cheapening  the  production  of  aluminium  chloride,  or  of 
aluminium-sodium  chloride. 

2nd.  Substituting  for  these  chlorides  some  other  cheaper  anhy- 
drous compounds  of  aluminium  not  containing  oxygen. 

3rd.  Cheapening  sodium. 

4th.  Replacing  sodium  by  a  cheaper  reducing  agent. 

Mr.  Weldon  exhibited  the  relative  cost  of  the  materials  used 
in  making  aluminium  as  then  carried  on  by  M.  Pechiney  as — 

Producing  the  alumina 10  per  cent. 

"       double  chloride  .         .         .         .     33 

"         "       sodium  and  reducing  therewith  .     57       " 

"  Discussing  these  figures,  it  is  seen  that  the  cost  of  the  alu- 
mina forms  but  a  small  item  in  the  cost  of  the  metal,  since  a 
saving  of  50  per  cent,  in  its  cost  would  only  cheapen  the  metal 
5  per  cent.  A  large  margin  is,  however,  left  in  the  conversion 
of  the  alumina  into  the  chloride,  and  it  is  here  that  a  large  saving 
may  be  expected  either  in  cheaper  methods  of  producing  the 
chloride  or  by  the  substitution  of  some  other  cheaper  salt  for  the 
chloride.  The  only  other  suitable  compounds  which  might  re- 
place the  latter  are  the  fluoride,  iodide,  bromide,  sulphide,  phos- 
phide, or  cyanide.  The  fluoride  has  been  used  to  some  extent  in 
the  form  of  cryolite,  but,  from  the  impurities  in  the  mineral  and 
its  corrosive  action  on  the  apparatus  used  for  reduction,  the  metal 
produced  is  very  much  contaminated  with  iron  and  silicon.  The 
bromide  and  iodide,  no  matter  how  produced,  would  always  be 
too  costly  to  replace  the  chloride.  The  production  of  the  sul- 
phide in  a  suitable  form  from  which  the  metal  can  be  extracted 
has  thus  far  not  proved  a  success  ;  and,  even  if  ever  it  be  thus  pro- 
duced in  a  suitable  condition,  it  is  not  at  all  likely  to  be  as  cheap 
a  material  to  use  as  the  chloride.  The  phosphide  and  cyanide 


30  ALUMINIUM. 

can  thus  far  only  be  produced  from  the  metal  itself,  and  are, 
therefore,  totally  out  of  the  question.  To  find  a  substitute  for 
sodium  as  a  reducing  agent  has  been  a  favorite  object  of  research 
among  chemists  for  the  past  thirty  years,  and  although  every  ele- 
ment occurring  in  any  abundance  or  obtainable  at  a  cheaper  rate 
than  sodium  has  been  tried  under  almost  all  conditions,  yet  abso- 
lutely nothing  has  been  accomplished  in  this  direction  that  would 
entitle  any  one  to  the  belief  that  aluminium  can  ever  be  pro- 
duced chemically  without  the  use  of  sodium.  So  absorbing  to 
those  interested  in  the  search  for  a  substitute  for  sodium  has  the 
occupation  proved,  that  the  effort  to  cheapen  sodium  did  not  re- 
ceive anything  like  its  fair  share  of  attention.  Since,  of  the  57 
per  cent,  ascribed  to  the  cost 'of  sodium  and  reduction,  50  per 
cent,  represents  the  sodium,  which  thus  costs  about  6  shillings  a 
pound,  there  is  seen  to  be  a  very  large  margin  for  improvements, 
since  the  raw  materials  for  a  pound  of  sodium  do  not  cost  over  1 
or  at  most  2  shillings." 

In  1882,  the  cost  of  aluminium  was  materially  cheapened  by 
the  application  of  the  inventions  of  Mr.  Webster,  which,  in  ac- 
cordance with  the  analysis  of  the  problem  made  by  Mr.  Weldoii, 
consisted  principally  in  the  cheap  production  of  alumina  and  its 
conversion  into  chloride.  Mr.  Webster  had  experimented  on  this 
subject  many  years,  and  in  1881  and  1882  took  out  patents  for 
his  processes  and  organized  the  "  Aluminium  Crown  Metal 
Company,"  located  at  Hollywood  near  Birmingham,  where  several 
thousand  pounds  were  expended  in  plant.  Business  was  soon 
commenced  on  a  large  scale,  the  company  producing,  however, 
niany  other  alloys  besides  those  of  aluminium.  The  business 
grew  until  it  soon  became  the  serious  competitor  of  the  French 
company,  and  practically  controlled  the  English  market.  How- 
ever, a  radical  change  of  still  greater  importance  in  the  sodium 
process  was  made  in  1886  by  an  invention  of  Mr.  H.  Y.  Cast- 
uer,  of  New  York  City.  This  gentleman  conceived  the  plan  of 
reducing  sodium  compounds  in  cast-iron  pots,  from  a  fused  bath 
of  caustic  soda,  by  which  the  reduction  is  performed  at  a  much 
lower  temperature  and  the  yield  of  sodium  is  very  much  more 
than  by  the  Deville  method.  The  application  of  this  process 
on  a  large  scale,  with  the  use  of  gas  furnaces  and  other  modern 


HISTORY   OF   ALUMINIUM.  31 

improvements,  has  lowered  the  cost  of  sodium  from  $1  per  pound 
to  about  20  or  25  cents.  It  is  but  just  to  say  that  Mr.  Castner7  s 
invention  was  by  no  means  a  chance  discovery.  For  four  years 
he  worked  in  a  large  laboratory  fitted  up  for  this  special  purpose, 
and  after  many  discouragements  in  trying  to  produce  aluminium 
by  means  other  than  that  of  sodium  was  led  finally  to  consider 
that  the  cheapening  of  this  metal  was  the  most  promising  method 
for  cheapening  aluminium,  and  after  much  patient,  hard  work, 
achieved  well-deserved  success. 

Mr.  Castner's  patent  was  taken  out  in  the  United  States  in 
June,  1886,  and,  while  being  the  first  one  granted  on  that  sub- 
ject in  this  country,  was  said  also  to  be  the  only  one  taken  out  in 
the  world  since  1808.     With  the  assistance  of  Messrs.  J.  H.  and 
Henry  Booth,  of  New  York  City,  Mr.  Castner  demonstrated  the 
process  by  building  and  operating  a  furnace  on  a  somewhat  large 
scale.     This  being  accomplished,  Mr.  Castner  crossed   to  Eng- 
land and  met  the  representatives  of  the  Webster  process,  with 
whom  it  was  evident  a  combination  would  be  especially  advan- 
tageous to  both  parties ;  for,  with  cheap  aluminium  chloride  and 
cheap  sodium,  it  was  clear  that  a  strong  process  could  be  built 
up.     Mr.  Castner  then  demonstrated  plainly,  by  erecting  a  fur- 
nace and  operating  it  for  several  weeks,  that  his  process  was  all 
that  he  claimed  for  it.     As  the  result  of  this  success,  the  "Alu- 
minium Company,  Limited"  was  incorporated   in  June,  1887, 
with  a  share  capital  of  £400,000,  ato  acquire  the  patents  and 
work  and  develop  the  inventions  of  James  Webster  for  the  manu- 
facture of  pure  alumina  and  certain   metallic  alloys  and  com- 
pounds, together  with  the  business  at  present  carried  on  by  the 
Webster  Patent  Aluminium  Crown  Metal  Company,  Limited,  in 
Birmingham,  Sheffield,  and  London,  England ;  and  also  to  ac- 
quire the  patents  and  work  and  develop  the  invention  of  H.  Y. 
Castner  for  the  manufacture  of  sodium  and  potassium."     Mr. 
Webster  was  paid  £230,000  for  the  business,  properties,  stock, 
etc.,  of  the  Crown  Metal  Company,  while  £140,000  was  allowed 
for  the  sodium  patents.     The  new  company  appointed  Mr.  Cast- 
ner managing  director,  and  the  erection  of  large  works  was  im- 
mediately begun  at  Oldbury,  near  Birmingham.     These  works 
were  started  in  operation  at  the  end  of  July,  1888.     They  cover 


32  ALUMINIUM. 

five  acres  of  ground,  and  have  an  annual  producing  capacity  of 
100,000  Ibs.  of  aluminium.  This  plant  is,  at  present,  the  largest 
aluminium  works  in  the  world,  and  in  view  of  the  large  part 
contributed  to  the  establishment  of  this  works  by  the  genius  of 
Mr.  Castner,  the  methods  there  used  are  rightly  called  "The 
Deville-Castner  Process." 

We  have  followed  the  progress  of  the  Webster  and  Castner  pro- 
cesses up  to  the  date  of  starting  the  works  at  Oldbury  because  the 
continuity  of  the  advances  made  in  the  old  Deville  process  would 
hardly  allow  of  a  break  in  order  to  mention  other  processes  aris- 
ing meanwhile.  However,  the  five  years  since  1884  have  wit- 
nessed not  one  but  several  revolutions  in  the  aluminium  industry. 
The  great  advances  made  in  dynamo-electric  machinery  in  the 
last  decade  have  led  to  the  revival  of  the  old  methods  of  elec- 
trolysis discovered  by  Deville  and  Bunsen,  and  to  the  invention 
of  new  methods  of  decomposing  aluminium  compounds  electro- 
lytically.  It  will  be  recalled  that  the  first  small  pencils  of  alu- 
minium made  by  Deville  were  obtained  by  electrolysis,  and  that 
he  turned  back  to  the  use  of  the  alkaline  metals  solely  because 
the  use  of  the  battery  to  eifect  the  decomposition  was  far  too  costly 
to  be  followed  industrially.  This  fact  still  holds  true,  and  we 
cannot  help  supposing  that  if  Deville  had  had  dynamos  at  his 
command  such  as  we  have  at  present,  the  time  of  his  death  might 
have  seen  the  aluminium  industry  far  ahead  of  where  it  now  is. 

First  in  point  of  time  we  notice  Gratzel's  process,  patented  in 
Germany  in  1883  and  used  industrially  by  the  "Aluminium  and 
Magnesium  Fabrik,  Patent  Gratzel"  at  Hemelingen  near  Bre- 
men. The  process  was  essentially  the  electrolysis  of  a  bath 
of  fused  aluminium  salt,  such  as  chloride  or  fluoride,  the  improve- 
ments on  the  older  experiments  being  in  details  of  apparatus  used, 
the  use  especially  of  anodes  of  mixed  carbon  and  alumina,  and 
the  use  of  dynamic  electricity.  Several  metallurgists  maintained 
the  uselessness  of  the  Gratzel  processes,  and  their  position  was 
proved  to  be  not  far  from  the  truth,  for  in  October,  1887,  the  com- 
pany announced  that  the  addition  "  Pt.  Gratzel"  would  be  drop- 
ped from  the  firm  name,  since  they  had  abandoned  Gratzel's  pro- 
cesses and  were  making  aluminium  by  methods  devised  by  Herr 


HISTORY   OF   ALUMINIUM.  33 

Saarburger,  director  of  therr  works.  The  processes  of  this  latter 
gentleman  not  being  published,  we  are  unable  to  state  their  nature, 
but  they  are  very  probably  electrolytic.  In  October,  1888,  Mr. 
Saarburger  reports  that  their  works  are  producing  at  the  rate  of 
12000  kilos  of  aluminium  yearly,  besides  a  large  quantity  of 
aluminium  bronze  and  ferro-aluminium.  The  firm  also  works 
up  the  aluminium  and  its  alloys  into  sheet,  wire,  tube,  etc. 

A  somewhat  similar  electrolytic  process  was  patented  by  Dr.  Ed. 
Kleiner,  of  Zurich,  in  1886.  Molten  cryolite  was  decomposed  by 
two  carbon  poles,  the  heat  generated  by  the  current  first  melting 
the  cryolite  and  then  electrolyzing  it.  Since  the  motive  power  in 
this,  as  in  all  electric  processes,  composes  one  of  the  chief  elements 
for  carrying  on  the  reduction,  the  Kleiner  Gesellschaft,  formed  to 
work  this  method,  made  an  attempt  to  obtain  water  rights  at  the 
falls  of  the  Rhine,  at  Schaffhausen,  which  would  furnish  15,000 
horse-power.  This  proposition  being  refused  by  the  government, 
an  experimental  plant  was  started  at  the  Hope  Mills,  Tyldesley, 
Lancashire,  England,  which  is  in  operation  at  present;  but  its 
commercial  success  seems  still  to  depend  on  a  more  economical 
application  of  the  electric  power  and  the  obtaining  of  metal  of 
greater  purity  than  is  usually  made  from  cryolite. 

An  electrolytic  method,  which  is  probably  superior  to  both  the 
preceding,  is  the  invention  of  Mr.  Chas.  M.  Hall,  of  Oberlin, 
Ohio,  which  was  patented  in  the  United  States,  April,  1889,  but 
which  has  already  been  in  successful  operation  for  nearly  a  year. 
Mr.  Hall  is  a  graduate  of  Oberlin  College,  and  for^  several  years 
experimented  on  a  small  scale,  overcoming  many  discouragements, 
at  last  perfecting  the  process  which  is  now  being  operated  by  the 
Pittsburgh  Reduction  Company  on  Fifth  Avenue,  Pittsburgh ; 
Mr.  Alfred  E.  Hunt,  a  well-known  metallurgist,  being  president 
of  the  company.  The  principle  involved  is  different  from  that  in 
either  the  Gratzel  or  the  Kleiner  process ;  it  is  the  electric  de- 
composition of  alumina  suspended  or  dissolved  in  a  fused  bath  of 
the  salts  of  aluminium  and  other  bases,  the  current  reducing  the 
alumina  without  affecting  its  solvent.  At  present  the  plant  is 
turning  out  50  to  75  Ibs.  of  aluminium  a  day,  and  is  so  successful 
as  to  first  cost  that  during  1889  they  sold  aluminium,  guaranteed 
98  per  cent,  pure,  at  $4.50  per  pound,  the  lowest  figure  the  metal 
3 


34  ALUMINIUM. 

had  ever  touched;  but  in  November,  1889,  they  captured  the 
aluminium  market  by  cutting  the  price  to  $2.00,  for  which 
achievement  Mr.  Hall  is  to  be  heartily  congratulated. 

While  the  electrolytic  processes  so  far  considered  use  a  fluid 
bath  and  operate  at  moderate  temperatures  with  a  current  of 
moderate  intensity,  there  have  been  devised  two  other  prominent 
processes  which  operate  in  a  somewhat  different  manner  and  at- 
tain to  very  economical  results.  These  primarily  depend  on  the 
enormous  temperature  attainable  by  the  use  of  a  powerful  electric 
arc,  and  secondarily  on  the  reduction  of  alumina  (which  at  the 
temperature  attained  becomes  fluid)  either  by  the  reducing  action 
of  the  carbon  present  or  by  simple  electric  decomposition. 
Which  of  these  two  agencies  performs  the  reduction,  in  either 
process,  is  still  an  unsettled  question  which  we  will  discuss  later 
on. 

Before  going  further  with  the  history  of  these  two  processes, 
Cowles*  and  Heroult's,  it  may  not  be  inappropriate  to  take  note 
of  a  few  facts  antecedent  to  their  appearance.  It  is  well  known 
that  Sir  W.  Siemens  devised  an  electric  furnace  in  which  the  heat 
of  the  arc  was  utilized  for  melting  steel.  In  1882,  Mr.  Ludwig 
Grabau,  in  Hanover,  Germany,  purchased  a  Siemens  furnace 
for  the  express  purpose  of  attempting  the  reduction  of  alumina, 
and  after  experimenting  successfully  for  some  time,  modified  the 
apparatus  so  as  to  work  it  continuously,  and  therewith  made 
aluminium  alloys;  but  on  account  of  the  difficulties  of  the  pro- 
cess and  the  Jrnpurity  of  the  alloys  produced,  Mr.  Grabau  gave 
up  the  experiments,  having  come  to  the  conclusion  that  alumin- 
ium alloys  to  be  technically  valuable  should  be  obtained  in  a 
state  of  almost  chemical  purity.  In  the  beginning  of  1885,  Dr. 
Mierzinski,  in  his  book  on  aluminium,  presented  some  very  striking 
remarks  on  the  use  of  the  electric  furnace,  which  are  so  much  to 
the  point  that  they  are  well  worth  quoting  in  this  connection  : 
"  The  application  of  electricity  for  producing  metals  possesses  the 
advantage  not  to  be  ignored  that  a  degree  of  heat  may  be  attained 
with  it  such  as  cannot  be  reached  by  a  blowpipe  or  regenera- 
tive gas-furnace.  The  highest  furnace  temperature  attainable  is 
2500°  to  2800°  C.,  but  long  before  this  point  is  reached  the  com- 
bustion becomes  so  languid  that  the  loss  of  heat  by  radiation 


HISTORY   OF   ALUMINIUM.  35 

almost  equals  the  production  of  heat  by  combustion,  and  hinders 
a  farther  elevation  of  temperature.  But  in  applying  electricity 
the  degree  of  heat  attainable  is  theoretically  unlimited.  A  fur- 
ther advantage  is  that  the  smelting  takes  place  in  a  perfectly 
neutral  atmosphere,  the  whole  operation  going  on  without  much 
preparation  and  under  the  eyes  of  the  operator.  Finally,  in 
ordinary  furnaces  the  refractory  material  of  the  vessel  must  stand 
a  higher  heat  than  the  substance  in  it,  whereas  by  smelting  in  an 
electric  furnace  the  material  to  be  fused  has  a  higher  temperature 
than  the  crucible  itself.  Since  the  attempt  to  produce  aluminium 
by  the  direct  reduction  of  alumina  by  carbon  is  considered  by 
metallurgists  as  impossible,  because  the  temperature  requisite  is 
not  attainable,  the  use  of  the  electric  current  for  attaining  this 
end  seems  to  be  of  so  much  the  more  importance." 

The  Cowles   invention  was  patented  August  18,   1885,  and 
was  first  publicly  described  before  the  American  Association  for  the 
Advancement  of  Science,  at  their  Ann  Harbor  meeting,  August 
28,  1885.     The  process  is  due  to  two  Cleveland  gentlemen,  E. 
H.  and  A.  H.  Cowles,  who  in  the  development  of  their  process 
associated  with    them    Prof.   Charles    F.   Mabery,  of  the  Case 
School  of  Applied  Science,  Cleveland,  as  consulting  chemist.     The 
Cowles  Electric  Smelting  and  Aluminium  Company,  formed  to 
work  the  process,  erected  a  plant  at  Lockport,  N.  Y.,  where  a 
water  power  of  1200  horse-power  was  secured,  and  where,  among 
other  novel  apparatus,  the  largest  dynamo  in  the  world,  made 
especially  for  this  purpose  by  the  Brush  Electric  Company,  is  in 
operation.     Following  the  success  of  this  plant  in  America,  the 
Cowles  Syndicate  Company,  organized  to  work  the  patents  in 
England,  have  put  in  operation  works  at  Stoke-on-Trent  which 
have  a  capacity  of  something  like  300  Ibs.  of  alloyed  aluminium 
daily.     Springing  also  from  the  Cowles  process  is  the  "  Alumi- 
nium Brass  and  Bronze  Company,"  of  Bridgeport,  Conn.,  which 
was  organized  in  July,  1887,  and  controls  the  exclusive  rights 
under  the  Cowles  American  patents  of  manufacturing  the  allovs 
of  aluminium  into  sheet,  rods,  and  wire.     The  extensive  plant 
which  this  company  is  starting  will  employ  300  men,  and  has 
been  erected  at  a  cost  of  nearly  $300,000. 

The  principle  made  use  of  in  the  Cowles  process  is,  briefly, 


36  ALUMINIUM. 

that  a  powerful  electric  current  is  interrupted,  the  terminals  being 
large  carbon  rods,  and  the  space  between  having  been  filled  with 
a  mixture  of  alumina,  carbon,  and  the  metal  to  be  alloyed,  the 
intense  heat  generated  in  contact  with  this  mixture  causes  the 
metal  to  melt  and  the  alumina  to  be  reduced  to  aluminium,  which 
combines  with  the  metal,  while  the  oxygen  escapes  as  carbonic 
oxide. 

It  is  interesting  to  note  as  separating  the  Cowles,  as  well  as 
the  Heroult,  process  from  the  previously  mentioned  electrolytic 
methods,  that  while  the  latter  produce  almost  exclusively  pure 
aluminium  in  their  electric  operation,  finding  it  inexpedient,  if 
not,  perhaps,  impossible  to  add  other  metals  and  form  alloys  at 
once — the  former  experience  almost  the  reverse  of  these  condi- 
tions, and  as  yet  are  confined  exclusively  to  the  direct  produc- 
tion of  the  alloys. 

The  Heroult  process  was  first  put  in  practical  operation  on 
July  30th,  1888,  at  the  -works  of  the  Swiss  Metallurgic  Company 
(Societe  Metallurgique  Suisse),  at  Neuhausen,  near  Scbaffhausen. 
The  patents  for  the  process  were  granted  in  France  and  England 
in  April  and  May,  1887,  and  in  the  United  States  in  August,  1888. 
The  company  named  above  is  composed  of  some  of  the  largest 
metal  workers  in  Switzerland.  Previously  to  their  adoption  of 
this  process  they  had  experimented  with  Dr.  Kleiner's  electrolytic 
method,  but  abandoned  it,  and  on  becoming  the  owners  of  the 
Heroult  process  immediately  started  it  up  practically  on  a  large 
scale,  and  with  signal  success. 

The  process  consists  in  electrolyzing  molten  alumina  which 
has  been  rendered  fluid  by  the  heat  of  the  arc,  using  as  the 
positive  anode  a  large  prism  of  hard  carbon  and  as  the  negative 
a  sub-stratum  of  molten  copper  or  iron,  the  arrangement  of  the 
parts  being  such  that  the  process  seems  to  proceed,  when  once 
well  under  way,  in  all  respects  as  the  simple  electrolysis  of  a 
liquid.  Using  water  power  for  driving  the  dynamos,  the  econom- 
ical production  of  alloyed  aluminium  at  4.5  francs  per  kilo  (50 
cents  per  pound),  is  said  to  be  an  assured  fact. 

The  success  of  this  process  at  Neuhausen  was  so  marked  as  to 
attract  general  attention,  and  in  the  latter  months  of  1888  several 
large  German  corporations,  prominent  among  which  was  the 


HISTORY   OF   ALUMINIUM.  37 

Allgemeine  Electricitats  Gessellschaft  of  Berlin,  sent  representa- 
tives to  arrange  for  the  purchase  of  the  Heroult  patents  for 
Germany.  The  outcome  of  these  examinations  and  negotiations 
was  the  purchase  by  this  German  Syndicate  of  Heroult's  conti- 
nental patents  and  the  founding  by  them  and  the  former  S\wss 
owners  of  the  Aluminium  Industrie  Actien-Gesellschaft,  with  a 
capital  of.  10,000,000  francs.  In  December,  1888,  the  new  com- 
pany took  possession  at  Neuhausen,  and  commenced  the  construc- 
tion of  a  plant  many  times  larger  than  the  original  one,  their 
plans  also  including  the  erection  of  foundries  and  mills  for 
casting  and  manufacturing  their  alloys.  Dr.  Kiliani,  the  well- 
known  writer  on  electro-metallurgical  subjects,  is  working  manager 
for  the  new  company.  The  new  plant  will  utilize  about  3000 
horse-power,  and  will  have  a  capacity  of  20  to  25  tons  of  10  per 
cent,  bronze  daily. 

Besides  these  works,  we  learn  that  a  French  company,  the 
Societe  Electro-Metallurgique,  has  commenced  the  manufacture 
of  alloys  by  the  Heroult  process,  their  works  at  Froges  (Isere) 
being  equal  to  a  daily  output  of  3000  kilos  of  10  per  cent,  bronze. 
Mr.  Heroult  was  also  in  the  United  -States  May- August,  1889, 
for  the  purpose  of  establishing  a  plant.  The  works  were  located 
at  Bridgeport,  Conn.,  and  were  started  in  August,  but  after  run- 
ning a  few  hours  the  dynamo  was  burnt  out  and  operations 
summarily  stopped  until  the  arrival  of  a  dynamo  ordered  from 
the  Oerlikon  works  at  Zurich.  This  is  hoped  to  be  in  place 
before  the  end  of  1889,*  and  the  works  in  full  operation. 

Both  the  Cowles  and  Heroult  processes  have  been  successful  in 
producing  aluminium  in  alloys  at  a  cost  far  below  that  at  which 
pure  aluminium  is  made,  and  they  apparently  have  a  good  pros- 
pect of  holding  this  position  for  some  time  to  come.  Comparing 
.  the  two  processes  we  see  that  while  on  first  sight  the  principle 
made  use  of  appears  similar,  yet  the  different  disposition  of  the 
parts  and  the  evidently  more  economical  working  in  the  case  of 
the  latter  seem  to  point  to  some  deep-seated  difference  in  the  re- 
actions made  use  of  in  the  two  cases.  However,  we  shall  more 
minutely  discuss  these  points  in  their  proper  place,  suffice  it  to 
say,  in  summing  up,  that  while  the  Cowles  process  undoubtedly 


38  ALUMINIUM. 

has  the  merit  of  having  been  first  in  the  field,  the  Heroult  has 
the  advantage  of  more  practical  and  economical  application. 

Among  the  many  other  aluminium  processes  and  companies 
which  have  been  projected  within  the  last  few  years,  we  notice 
prominently  the  Alliance  Aluminium  Company  of  London,  Eng- 
land, organized  in  the  early  part  of  1888.  Having  a  nominal  capi- 
tal of  £500,000,  it  is  said  to  own  the  English,  German,  French,  and 
Belgian  patents  of  Prof.  Xetto,  of  Dresden,  for  the  manufacture 
of  sodium  and  potassium  and  the  reduction  of  cryolite  thereby ; 
the  patents  of  Mr.  Cunningham  for  methods  of  reduction  of  the 
same  metals;  and  methods  devised  by  Prof.  Netto  and  Dr. 
Saloman,  of  Essen,  for  producing  aluminium  of  great  purity  on 
a  commercial  scale.  The  two  latter  named  gentlemen  are  said  to 
have  invented  their  processes  after  long  experimenting  at  Krupp's 
works  at  Essen ;  and,  since  the  apparatus  used  was  mounted  on 
trunnions,  many  rumors  have  been  spread  by  the  newspapers  that 
aluminium  was  being  made  (by  tons,  of  course)  in  a  Bessemer  con- 
verter by  Krupp,  of  Essen.  Prof.  Netto  reduces  sodium  by  a 
continuous  process,  by  allowing  fused  caustic  soda  to  trickle  over 
incandescent  charcoal  in  a  vertical  retort,  the  apparatus  contain- 
ing many  ingenious  details  and  giving  promise  of  being  quite 
economical.  One  method  of  using  the  sodium  in  reduction  con- 
sists in  the  use  of  a  plunger  to  which  bars  of  sodium  are  attached 
and  held  at  the  bottom  of  a  crucible  full  of  molten  cryolite ; 
another  depends  on  the  use  of  a  revolving  cylinder  in  which  the 
cryolite  and  sodium  react,  and  appears,  more  chimerical  than 
Netto's  other  propositions.  This  latter  device,  however,  is  said 
to  be  in  operation  at  Essen,  though  with  what  success  we  cannot 
learn. 

In  June,  1888,  "Engineering"  stated  that  the  Alliance  Com- 
pany were  located  at  King's  Head  Yard,  London,  E.  C.,  and 
that  several  small  reduction  furnaces  were  being  operated,  each 
producing  about  50  Ibs.  of  aluminium  a  day,  estimates  of  the 
cost  at  which  it  was  made  giving  6  to  8  shillings  per  pound.  In 
the  early  part  of  1889  there  seems  to  be  a  division  of  the  original 
company.  The  "Alkali  Reduction  Syndicate,  Limited"  have 
leased  ten  acres  of  ground  at  Hepburn  on  which  to  erect  a  plant 
for  working  Cunningham's  sodium  patents,  the  sodium  produced 


HISTORY   OF   ALUMINIUM.  39 

going  to  the  Alliance  Company's  reduction  works  located  at 
Wallsend. 

As  to  the  exhibit  made  by  this  company  at  the  Paris  Exhibi- 
tion, 1889,  we  will  have  some  remarks  to  make  later  on. 

Ludwig  Grabau,  of  Hanover,  Germany,  has  made  several 
patented  improvements  in  producing  aluminium,  which  are  in  the 
same  direction  as  Prof.  Netto's  methods.  Mr.  Grabau  believes 
that  in  order  that  aluminium  may  possess  its  most  valuable  quali- 
ties, both  for  use  alone  or  in  alloying,  it  should  be  of  almost 
chemical  purity ;  and  as  the  best  means  of  attaining  this  end 
economically  he  has  improved  the  sodium  method  011  these  three 
lines : — 

1st.  Production  of  cheap  pure  aluminium  fluoride. 

2d.  Production  of  cheap  sodium. 

3d.  Reduction  in  such  a  manner  that  no  possible  impurities 
can  enter  the  reduced  metal,  and  that  the  sodium  is 
completely  utilized. 

How  far  Mr.  Grabau  has  succeeded,  as  regards  cheap  produc- 
tion, I  cannot  say,  but  as  for  the  purity,  a  sample  sent  the 
author  contains  99.8  per  cent,  of  aluminium,  and  is  undoubtedly 
the  purest  made  at  present  in  the  world.  Mr.  Grabau's  sodium 
patents  are  now  pending,  but  his  other  processes  are  described  in 
full  in  their  appropriate  places. 

"  The  American  Aluminium  Company,"  of  Milwaukee,  Wis., 
was  organized  in  July,  1887,  with  a  capital  of  $1,000,000,  to  manu- 
facture aluminium  by  a  process  of  Prof.  A.  J.  Rogers.  The 
process  is  kept  secret,  the  application  made  for  patents  not  being 
yet  granted,  but  the  means  used  are  electrolytic  and  not  very  dif- 
ferent in  principle  from  some  others  recently  granted  in  England. 
A  small  experimental  plant  put  up  in  the  summer  of  1888  has 
given  encouraging  results  as  to  the  purity  of  metal  obtainable 
and  the  yield,  and  it  is  not  improbable  that  if  patents  are  granted 
soon  the  company  will  have*  a  larger  plant  in  operation  and  their 
metal  on  the  market  in  the  early  months  of  1890. 

There  is  a  company  hailing  from  Kentucky,  about  whose 
methods  no  reliable  information  is  to  be  had,  the  numerous  news- 
paper articles  which  it  has  inspired  being  glaringly  inaccurate  and 


40  ALUMINIUM. 

sensational,  while  our  more  staid  scientific  journals  seem  to  treat  it 
on  the  principle  of  "  the  least  said  the  better."  The  enterprise 
was  first  brought  to  public  notice  in  June,  1888,  by  an  Associated 
Press  dispatch,  stating  that  by  reducing  common  clay  and  cryolite 
in  steel  water-jack etted  cupola  furnaces,  pure  aluminium  was  ob- 
tained very  cheaply.  Two  months  later  the  ridiculous  statement 
went  the  rounds  of  the  press  that  this  concern  had  exported  150 
Ibs.  of  pure  metallic  aluminium  to  London,  England,  selling  it  at 
50  cents  per  Ib.  Since  then,  advertisements  have  appeared  in  the 
newspapers  claiming  them  to  be  the  only  manufacturers  of  pure 
aluminium  in  America,  oifering  it  at  $5  per  pound,  and  also  offer- 
ing for  sale  various  aluminium  bronzes,  ferro-aluminium,  alumin- 
ium solders,  etc.  Later  accounts  of  some  methods  used  seem  to 
point  to  the  utilization  of  the  idea  of  coating  scrap  iron  with 
clay  and  "  certain  fluxes"  and  then  running  it  down  in  a  water- 
jacketted  cupola,  the  castings  being  said  to  contain  1 J  per  cent,  of 
aluminium.  This  method  is  identical  with  one  recently  patented 
by  other  parties  in  England  and  on  the  Continent.  Whether  this 
company  produces  aluminium  or  not  is  a  question  ojily  answered 
by  some  very  unreliable  newspaper  statements  in  the  affirmative. 
The  process  last  referred  to  is  apparently  successful  in  England, 
and  may  quite  probably  give  the  results  claimed  by  this  company, 
but  of  the  process  for  making  pure  aluminium  we  can  only  say 
that  it  does  not  appear  to  be  possible. 

Colonel  William  Frishmuth,  of  Philadelphia,  is  a  German 
chemist  whose  name  has  been  often  published  in  connection  with 
aluminium.  Before  1860,  Col.  Frishmuth  operated  a  small 
chemical  works  on  North  Broad  Street,  Philadelphia,  and  there 
followed  the  production  of  sodium  by  Deville's  methods,  furnishing 
it  to  the  chemical  dealers.  It  is  quite  possible  that  he  followed 
Deville's  methods  still  further,  and,  by  means  of  sodium,  pro- 
duced aluminium  in  small  quantities.  In  1877,  Col.  Frishmuth 
was  operating  a  small  electro-plating  works  in  the  northern  part 
of  Philadelphia,  claiming  to  plate  an  alloy  of  nickel  and  alumin- 
ium from  aqueous  solution.  While  engaged  in  this,  he  persuaded 
some  gentlemen  in  the  metal  trade  to  aid  him  financially  in  de- 
veloping a  process  for  making  aluminium,  but  always  stipulating 


HISTORY   OF   ALUMINIUM.  41 

that  he  be  allowed  to  retain  the  secret  of  the  process.  Led  on 
by  reports  of  successes  and  promises  of  returns  in  the  near  future 
these  gentlemen  invested  several  thousand  dollars  with  the  sole 
result  of  reports  of  progress  and  fresh  requests  for  money.  After 
several  years  waiting,  one,  at  least,  of  these  gentlemen  lost  faith 
in  the  truth  of  Frishmuth's  statements  and  withdrew  his  support, 
losing  all  that  he  had  advanced.  Other  capitalists,  however, 
were  induced  to  step  forward  and  put  money  into  the  concern, 
having  nothing  but  the  statements  and  promises  of  Frishrnuth 
as  their  security.  Again  others,  in  disgust,  threw  up  their  in- 
terest in  the  affair,  never  regaining  a  cent  of  what  had  been  ad- 
vanced. I  have  been  thus  minute  in  these  statements  because 
this  is  a  sample  of  the  whole  history  of  the  process.  In  1884, 
Col.  Frishmuth  obtained  a  patent  for  producing  aluminium  by 
simultaneously  generating  sodium  vapor  in  one  retort,  vapor  of  a 
volatile  aluminium  salt  in  another,  and  mixing  the  vapors  in 
a  third  retort,  where  they  were  to  react  and  form  aluminium. 
The  process  was  never  successful,  and  Frishmuth  has  since 
abandoned  altogether  the  use  of  sodium  and  has  been  experi- 
menting of  late  years  with  electrolytic  methods.  On  the  obtain- 
ing of  this  patent  an  English  syndicate  sent  Major  Ricarde-Seaver, 
F.R.S.E.,  to  this  country  to  report  on  the  process.  Major 
Seaver  was  not  altogether  convinced,  from  what  he  was  allowed 
to  see,  of  the  practicability  of  the  furnace,  and  on  reporting  to 
the  syndicate,  a  very  liberal  offer  was  made  to  Frishmuth,  pro- 
posing that  he  come  to  England,  erect  a  furnace,  and  demon- 
strate its  working  in  a  fair,  clear  manner,  the  syndicate  to  pay  all 
the  expenses  incident  to  the  test,  including  Col.  Frishmuth's  per- 
sonal expenses.  This  offer  was  refused,  for  what  reason  we  need 
not  go  far  to  find.  Since  this  episode  other  capitalists  at  home 
have  advanced  the  funds  which  were  asked  for,  and  aluminium 
has  been  sold  in  moderate  quantities,  though  how  it  is  made, 
or  whether  Col.  Frishmuth  produces  it  or  not,  is  an  unsettled 
question.  The  metal  sold  is  unquestionably  of  good  quality, 
averaging  as  nearly  as  can  be  the  same  as  the  best  French  metal ; 
it  is  quite  probable  that  with  his  long  experience  in  handling 
the  metal  Col.  Frishmuth  is  quite  expert  in  refining  and  running 
down  aluminium  scrap  of  all  kinds — undoubtedly  a  difficult 


42  ALTTMINIUM. 

thing  to  do.  In  1884-5,  the  Philadelphia  Business  Census  re- 
corded him  as  employing  ten  men  and  his  annual  product  as 
valued  at  $18,000,  but  since  then  Col.  Frishmuth  has  grown  un- 
communicative to  the  census  reporter,  so  that  in  1886  it  was  stated 
in  the  Government  Report  on  the  Mineral  Resources  of  the 
United  States  that  no  pure  aluminium  was  made  in  America  in 
that  year — a  statement  which  we  may  accept  as  correct.  Much 
public  interest  was  directed  to  Frishmuth  in  1884,  when  he  cast 
the  aluminium  cap  or  apex  of  the  Washington  Monument.  This 
casting  is  of  pyramidal  form,  10  inches  high,  6  inches  on  a  side  of 
its  base,  and  weighs  8  J  pounds.  An  analysis  of  the  metal  in  this 
casting  is  given  on  p.  54,  and  show^s  it  to  be  of  a  quality  equal  to 
the  best  French  aluminium. 

Two  aluminium  companies  have  come  to  the  author's  notice  of 
which  I  am  able  to  give  no  more  than  the  bare  fact  of  their  ex- 
istence. "  The  Aluminium  Company  of  America77  was  incorpo- 
rated under  the  laws  of  New  York,  with  a  capital  of  $1,500,000  ; 
Paul  R.  Pohl,  of  Philadelphia,  was  styled  the  mineralogist 
and  chemist.  I  do  not  think  that  the  company  has  ever  done 
anything  further  than  to  organize,  offer  stock,  and  issue  a  pros- 
pectus. It  is  now  extinct.  "  The  United  States  Aluminium 
Company,'7  of  East  St.  Louis,  was  incorporated  in  March,  1889, 
with  a  capital  of  $1,000,000,  for  the  purpose  of  manufacturing 
aluminium  and  its  alloys.  The  incorporators  of  the  company, 
process  to  be  used,  etc.,  are  unknown  to  the  author. 

We  will  close  this  historical  sketch  by  referring  the  reader  back 
to  Dr.  Winckler's  remarks  (p.  27),  and  supplementing  them  with 
a  notice  of  the  exhibits  of  aluminium  at  the  Paris  Exposition  of 
1889.  If,  as  Dr.  Winckler  remarks,  the  three  international  ex- 
hibitions in  1855,  1867,  and  1878  show  so  many  stages  in  its 
career,  it  is  quite  evident  that  the  exposition  of  1889  has  shown 
a  more  promising  view  of  the  industry  than  any  of  its  predecessors, 
excepting  perhaps  the  first.  It  was  not  unnatural  that  many 
hopes  were  disappointed  when  the  exhibit  of  1878  showed  so  lit- 
tle advance  over  that  of  1867,  and  when  the  fact  became  pain- 
fully evident  that  for  twenty  years,  1858  to  1878,  very  little  real 
progress  had  been  made  in  the  industry.  I  think  that  if  the 
exposition  of  1878  showed  anything  at  all,  it  showed  that,  from 


HISTORY   OF   ALUMINIUM.  43 

a  metallurgical  standpoint,  the  industry  was  at  a  stand-still. 
Against  this  we  place  the  exhibit  of  1889,  and  the  contrast  is 
striking ;  this  shows  not  deadness  but  the  most  intense  and  suc- 
cessful activity  that  the  industry  has  ever  known.  In  place  of 
one  exhibitor,  five  manufacturers  compete  for  honors.  In  short, 
this  last  exposition  has  shown  the  aluminium  industry  re-awakened 
and  rapidly  approaching  its  goal — the  placing  of  aluminium 
among  the  common  metals.  Just  now,  at  the  close  of  1889,  are 
we  not  almost  inclined  to  state,  in  view  of  recent  developments, 
that  it  has  reached  this  goal  ? 

As  to  the  exhibits  referred  to,  a  detailed  account  reads  as 
follows  : — Societe  Anonyme  pour  Flndustrie  de  P Aluminium  : 
In  a  large  case,  the  frame  of  which  was  aluminium  bronze, 
samples  of  aluminium,  ferro-aluminium,  aluminium  bronze, 
forged  and  rolled,  and  numerous  articles  of  the  latter  alloy. 
Cowles  Electric  Smelting  and  Aluminium  Company  :  Samples  of 
ferro-aluminium,  aluminium  bronze  and  aluminium  brass  of 
various  grades,  aluminium  silver,  and  numerous  useful  articles 
made  of  these  alloys.  Brin  Bros.  :  Samples  of  aluminium,  with 
thin  iron  and  steel  castings  made  by  its  use.  The  Alliance 
Aluminium  Company :  Two  large  blocks  of  aluminium,  cast 
hollow,  weighing  possibly  1000  pounds  and  500  pounds  respect- 
ively. The  inclosing  balustrade  and  decorations  were  princi- 
pally of  aluminium  or  aluminium  bronze.  The  Aluminium 
Company,  Limited  :  A  solid  casting  of  aluminium  bronze  weigh- 
ing J  ton,  and  on  this  a  solid  block  of  98  per  cent,  aluminium 
weighing  the  same.  In  the  corners  of  the  case  piles  of  ingots 
of  99  per  cent,  aluminium,  10  per  cent,  bronze,  5  per  cent, 
bronze,  10  per  cent,  ferro-aluminium,  and  20  per  cent,  alu- 
minium steel.  Besides  which  was  a  7  inch  bell,  springs,  statues, 
aluminium  plate,  round  and  square  tubes,  wire,  sheet,  etc.  Such 
were  the  aluminium  exhibits  which  attracted  as  much  interest  as 
the  historic  ingot  of  1855  did  at  its  debut;  and,  not  taking  into 
account  that  Mr.  HalFs  process  was  not  represented  and  that  the 
German  makers  were  debarred  from  exhibiting  because  of  inter- 
national pique,  yet  the  exhibit  shown  was  one  which  demonstrated 
the  great  advances  made  in  the  last  decade  and  give  cause  for  the 


44  ALUMINIUM. 

most  sanguine  hopes  for  the  future.  Indeed,  it  seems  more  than 
half  true  that  already  "aluminium — the  metal  of  the  future,  is 
transformed  into  aluminium — the  metal  of  the  present." 


STATISTICAL. 

The  following  table  shows  the  price  at  which  aluminium  has 
been  sold  since  it  was  first  placed  on  the  market. 

Date.  Place.  Per  kilo.  Per  pound. 

1856  (Spring)  Paris  .  .  .  .  1000  fr.  $90.90 

1856  (August)      "  .  .  .  .  300  "              27.27 

1859                        "  .  .  .  .  200  "              17.27 

1862  .     "  .  .  .  .  130  "              11.75 

1862  Newcastle  .  .  .                              11.75 

1878  Paris  .  .  .  .  130  "              11.75 

1886  "  .  .  .  .                              12.00 

1887  Bremen       .         .         .         .  8.00 

1888  London       ....  4.84 

1889  Pittsburgh  .         .         .  2.00 

The  selling  price  of  aluminium  bronze  has  until  recently  de- 
pended directly  on  the  price  of  pure  aluminium,  since  the  bronze 
was  made  by  simply  uniting  the  two  metals,  but  since  electrical 
methods  of  obtaining  the  bronze  directly  have  been  used  the 
alloy  has  been  sold  at  a  price  for  the  contained  aluminium  much 
below  what  pure  aluminium  could  be  bought  for.  The  ten  per 
cent,  bronze  has  been  sold  as  follows  : —  ' 

Date.  Place.                                                                 Per  kilo.  Per  pound. 

1878  Paris          .         ....  .     18.00  fr.  $1.64 

1885  Cowles  Bros.      .         .         .  .       4.50  "  0.40 

1888                  "          "                                            3.85  "  0.35 

1888  Heroult  process,  Neuhausen  .       3.30  "  0.30 

It  is  almost  impossible  to  estimate  how  much  aluminium  has 
been  made  since  Deville  first  started  the  industry.  The  following 
figures  of  annual  outputs  are  gleaned  from  various  sources,  some 
of  them  being  of  doubtful  accuracy. 


HISTORY   OF   ALUMINIUM.  45 

kg.  Ibs. 

a  55 

=  1584 
2112 
2400 

=    1000 
4000 
1650 
5170 
5280 
.   70 
.   125 
.  230 
.  450 
.  6500 
17800 

A  very  approximate  estimate  of  the  whole  amount  of  alumin- 
ium that  had  been  produced  up  to  1886,  made  from  a  careful 
comparison  and  study  of  the  above  reports,  gives  a  total  of 
115,000  Ibs.  (52,000  kilos).  Since  then  the  Cowles  Bros,  are 
reported  as  having  turned  out  50,000-60,000  Ibs.  in  alloys,  the 
Aluminium  Company,  Limited,  have  probably  made  as  much,  and 
the  Hemelingen  Fabrik,  which  has  been  in  operation  since  1885,  is 
now  producing  10,000-15,000  kilos  yearly  (22,000-33,000  Ibs.). 

The  amount  of  aluminium  imported  and  entered  for  consump- 
tion in  the  United  States  from  1870  to  1887  is  as  follows : — 


1854-56 

Deville      .... 

25 

1859 

Nanterre  (Deville)     . 

.      720 

1859 

Rouen  (Tissier  Bros.) 

.      960 

1865 

France       .... 

.    1090 

1869 

France       .... 

.      455 

1872 

Salindres  (H.  Merle  &  Co.) 

.    1800 

1872 

England  (Bell  Bros.) 

.      750 

1882 

Salindres 

.    2350 

1884 

Salindres 

.    2400 

1883 

Philadelphia  (Frishmutli) 

. 

1884 

"                     " 

. 

1885 

«                     it 

.         . 

1885 

Cowles  Bros,  (in  alloys) 

. 

1886 

«                a 

. 

1887 

a      .         " 

. 

Year  ending  June  30. 

Quantity  (pounds). 

Value. 

1870  . 

.     ...     — 

$  98 

1871  . 

— 

341 

1872  . 

— 

— 

1873  . 

2 

22 

]874  . 

183 

2125 

1875  . 

....   134 

1355 

1876  . 

139 

1412 

1877  . 

131 

1551 

1878  . 

251 

2978 

1879  . 

284 

3423 

1880  . 

341 

4042 

1881  . 

.    .    .    .    .517 

6071 

1882  . 

566 

6459 

1883  . 

426 

5079 

1884  . 

.    .    .    .   590 

8416 

1885  . 

439 

4736 

1886  . 

.  '  .    .464 

5297 

1887  . 

797 

9458 

1888  . 

1772 

16764 

46  ALUMINIUM. 


CHAPTEE  II. 

OCCURRENCE  OF  ALUMINIUM  IN  NATURE. 

THERE  is  no  other  metal  on  the  earth  which  is  so  widely  scat- 
tered and  occurs  in  such  abundance. 

Aluminium  is  not  found  metallic.  Stocker*  made  the  state- 
ment that  aluminium  occurred  as  shining  scales  in  an  alumina 
formation  at  St.  Austel,  near  Cornwall,  but  he  was  in  error.  But 
the  combinations  of  aluminium  with  oxygen,  the  alkalies,  fluorine, 
silicon,  and  the  acids,  etc.,  are  so  numerous  and  occur  so  abund- 
antly as  not  only  to  form  mountain  masses,  but  to  be  also  the 
bases  of  soils  and  clays.  Especially  numerous  are  the  combina- 
tions with  silicon  and  other  bases,  which,  in  the  form  of  felspar 
and  mica,  mixed  with  quartz,  form  granite. 

These  combinations,  by  the  influence  of  the  atmosphere,  air, 
and  water,  are  decomposed,  the  alkali  is  replaced  or  carried  away, 
and  the  residues  form  clays.  The  clays  form  soils,  and  thus  the 
surface  of  the  earth  becomes  porous  to  water  and  fruitful.  It  is 
a  curious  fact  that  aluminium  has  never  been  found  in  animals  or 
plants,  which  would  seem  to  show  that  it  is  not  necessary  to  their 
growth,  and  perhaps  would  act  injuriously,  if  it  were  present,  by 
its  influence  on  the  other  materials.  Most  of  the  aluminium 
compounds  appear  dull  and  disagreeable,  such  as  felspar,  mica, 
pigments,  gneiss,  amphibole,  porphyry,  eurite,  trachyte,  etc. ;  yet 
there  are  others  possessing  extraordinary  lustre,  and  so  beautiful 
as  to  be  classed  as  precious  stones.  Some  of  these,  with  their 
formulae,  are : — 

Ruby A12Q3 

Sapphire A1203 

Garnet .  (Ca.Mg.Fe.Mn)3A12Si3Qi2 

Cyanite Al2Si05 


Journ.  fr.  prakt.  Chem.,  66,  p.  470. 


OCCURRENCE   OF   ALUMINIUM   IN   NATURE.  47 

Some  other  compounds  occurring  frequently  are : — 

Turquoise A12p208.H<5A1206.2H20 

Lazulite (MgFe)Al*paO»  + Aq 

Wavellite 2A12P208.H6A1206.9H2 

Topaz 5Al2Si05.A12SiF10 

Cryolite Al2F6.6NaF 

Diaspore H2A12Q4 

Beauxite H6A1*06 

Alurainite         .         .         .         .         .         .  A12S06.9H2Q 

Al  unite K2S04.A12c3012.2H2A1206 

One  would  suppose  that  since  aluminium  occurs  in  such  abund- 
ance over  the  whole  earth  that  we  literally  tread  it  under  foot, 
it  would  be  extracted  and  applied  to  numberless  uses,  being  made 
as  abundant  and  useful  as  iron  ;  but  such  is  not  the  case. 

Beauxite  and  cryolite  are  the  minerals  most  used  for  producing 
aluminium,  and  their  preference  lies  mainly  in  their  purity.  Na- 
tive alums  generally  contain  iron,  which  must  be  removed  by 
expensive  processes. 

BEAUXITE. 

Beauxite  is  a  combination  between  diaspor,  A12O3.3H2O,  and 
brown  hematite,  Fe2O3.3H2O ;  or,  it  is  diaspor  with  aluminium 
replaced  more  or  less  by  iron  •  the  larger  the  amount  of  iron,  the 
more  its  color  changes  from  white  to  brown.  It  wras  first  found 
in  France,  near  the  town  of  Beaux,  large  deposits  occurring  in 
the  departments  of  Var  and  Benches  du  Rhon,  extending  from 
Tarascon  to  Antibes.  Several  of  these  beds  are  a  dozen  yards 
thick,  and  160  kilometers  in  length.  Deposits  are  also  found  in 
the  departments  of  1'Herault  and  PArriege.  Very  important 
beds  are  found  in  Styria,  at  Wochein,  and  at  Freisstritz,  in  Aus- 
tria, a  newly  discovered  locality  where  the  mineral  is  called 
Wocheinite.  Here  it  has  a  dense,  earthy  structure,  while  that  of 
France  is  conglomerate  or  oolitic.  Deposits  similar  to  those  of 
France  are  found  in  Ireland  at  Irish  Hill,  Straid,  and  Glenravel. 
Further  deposits  are  found  in  Hadamar  in  Hesse,  at  Klein  Stein- 
heim,  Langsdorff,  and  in  French  Guiana. 

The  following  analyses  give  an  idea  of  the  peculiar  composi- 
tion of  this  mineral ;  besides  the  ingredients  given  there  are  also 


48 


ALUMINIUM. 


traces  of  lime,  magnesia,  sulphuric,  phosphoric,  titanic  and  van- 
adic  acids. 


a. 

b. 

c. 

d. 

e. 

/. 

A1203   .  . 

60  0 

75  0 

63  16 

72  87 

44  4 

54  1 

Fe2G3   .   . 

25  0 

12  0 

23  55 

13  49 

30  3 

10  4 

SiO2  

3  0 

1.0 

4  15 

4  25 

15  0 

12  0 

K20  and  Na20   .  . 
H20  

12.0 

12.0 

0.79 
8.34 

0.78 
8.50 

9.7 

29  9 

ff- 

h. 

i. 

k. 

I. 

m. 

A1203   

64.6 

29.80 

48  12 

43  44 

61  89 

45  76 

Fe203   

2.0 

3.67 

2.36 

2  11 

1  96 

18  96 

SiO2  

7.5 

44.76 

7.95 

15  05 

6  01 

6  41 

K20  and  Na20   .  . 
H20  . 

24  7 

13  86 

40  33 

35  70 

27  82 

0.38 
27  61 

w. 

o. 

P- 

?• 

r. 

A12Q3      

55  61 

76  3 

50  85 

49  02 

73  00 

Fe203      

7  17 

6  2 

14  36 

12  90 

4  26 

SiO2  

4  41 

11.0 

5  14 

10  27 

2  15 

K20  and  Na20       .     . 
H20    

32.33 

26.4 

0.26 

28  38 

0.31 
25  91 

18  66 

Index  : — 


a  and 
c. 
d. 
e. 
f> 
9- 
h. 
i, 
k. 
I. 

m  and 
o, 
and 


b.  from  Beaux  (Deville). 

dark  1  Wocheinite  (Drecnsler). 

light  J 

red  brown   -» 


\  Beauxite  from  Feisstritz  (Schnitzer). 


yellow 

white 

white  Wocheinite  (L.  Mayer  and  0.  Wagner). 

Beauxite  from  Irish  Hill. 

"  "      Co.  Antrine  (Spruce). 

"      Glenravel  (F.  Hodges). 
n.        "  "      Hadamar  (Hesse)  (Retzlaff). 

from  Klein-Steinheim  (Bischof). 
7.  from  Langsdorff  (I.  Lang). 

Beauxite  from  Dublin,  Ireland,  brought  to  the  Laurel  Hill  Chemical 
Works,  Brooklyn,  L.  I.,  and  there  used  for  making  alums.  It  is 
dirty  white,  hard,  dense,  compact,  and  in  addition  to  the  ingre- 
'  dients  given  above  contains  0.59  per  cent,  of  lime,  and  some  titanic 
acid.  It  costs  $6  per  ton  laid  down  in  the  works.  The  above 
analysis,  made  by  Mr.  Joiiet,  is  furnished  me  by  the  kindness  of 
the  superintendent  of  the  works,  Mr.  Herreshoff'. 


OCCURRENCE   OF   ALUMINIUM    IX    NATURE.  49 

As  is  seen  from  the  above  analyses,  the  percentage  of  alumina 
is  very  variable,  and  cannot  be  determined  at  all  simply  by  in- 
spection, but  only  by  an  analysis,  for  often  the  best-looking  speci- 
mens are  the  lowest  in  this  base.  For  instance,  a  beauxite  con- 
taining 62.10  A12O3,  6.11  Fe2O3,  5.06  SiO2,  and  20.83  H2O  was 
much  darker  and  more  impure-looking  than  that  from  Wochein  (A), 
which  contained  only  29.8  per  cent,  of  alumina. 

Beauxite  has  until  recently  not  been  found  in  the  United 
States,  but  in  1887  a  deposit  was  discovered  in  Floyd  County,  Ga., 
which  is  described  as  follows  in  a  paper  read  by  Mr.  Edward 
Nichols  before  the  American  Institute  of  Mining  Engineers  at 
their  Duluth  meeting,  July,  1887. 

"  Numerous  float  specimens,  covering  an  area  of  about  one- 
half  an  acre,  indicate  the  location  of  the  main  deposit,  which  has 
thus  far  been  opened  to  an  inconsiderable  extent  only.  The 
excavations  show  the  beauxite  to  exist  apparently  as  large  masses 
in  clay.  The  formation  is  determined  by  the  Geological  Survey 
of  Georgia  to  be  Lower  Silurian.  The  surface  in  the  immediate 
vicinity  is  covered  with  numerous  fragments  of  chert,  a  charac- 
teristic rock  throughout  this  formation  in  Georgia.  An  exami- 
nation of  the  mineral  shows  it  to  have  the  oolitic  structure  com- 
mon to  several  beauxites.  It  varies  in  color  from  light-salmon 
to  dark-red,  according  to  the  content  of  iron  sesquioxide.  The 
light-colored  specimens  are  comparatively  soft,  while  the  dark- 
colored  are  much  harder,  spots  in  them  being  harder  than  quartz. 
The  chemical  composition  is  interesting  because  of  the  presence 
of  titanic  acid,  in  which  it  resembles  the  mineral  found  in  Asia 
Minor.  It  dissolves  with  difficulty  in  acids,  but  fuses  easily  with 
potassium  acid-sulphate.  Owing  to  the  purity  of  the  deposit,  it 
seems  likely  to  have  a  value  before  long  for  use  in  some  alu- 
minium reduction  process,  or  as  a  refractory  material." 

Analyses 
SiO2 
Al«08 
Fe203 
TiO2 
H20 
CaO 
MgO 

P2Q5 

4 


Dark  specimen. 
2.800 

Light  specimens. 
—            2.300 
57.248       56.883 
3.212         1.490 
3.600         3.551 

0.06J 

52.211 
13.504 

3.520 

27.721 
0.  — 

0.— 

50  ALUMINIUM. 


CRYOLITE. 

Cryolite  was  first  found  at  Ivigtuk  in  Arksut-fiord,  west  coast 
of  Greenland,  where  it  constitutes  a  large  bed  or  vein  in  gneiss. 
It  was  very  rare  even  in  mineralogical  collections  until  1855,  when 
several  tons  were  carried  to  Copenhagen  and  sold  under  the  name 
of  "  soda  mineral."  It  is  a  semi-transparent,  snow-white  mineral. 
When  impure  it  is  yellowish  or  reddish,  even  sometimes  almost 
black.  It  is  shining,  sp.  gr.  2.95,  and  hardness  2.5  to  3.  It  is 
brittle,  not  infrequently  contains  ferrous  carbonate,  sulphide  of 
lead,  silica,  and  sometimes  columbite.  It  is  fusible  in  the  flame  of 
a  candle,  and  on  treatment  with  sulphuric  acid  yields  hydrofluoric 
acid.  As  will  be  seen  further  on,  cryolite  was  first  used  by  the 
soap-makers  for  its  soda ;  it  is  still  used  for  making  soda  and 
alumina  salts,  and  to  make  a  white  glass  which  is  a  very  good 
imitation  of  porcelain.  The  Pennsylvania  Salt  Company  in 
Philadelphia  import  it  from  Ivigtuk  by  the  shipload  for 
these  purposes  ;  lately  they  have  discontinued  making  the  glass. 
Cyrolite  is  in  general  use  as  a  flux.  A  very  complete  description 
of  the  deposit  at  Ivigtuk  can  be  found  in  Hoffman's  "  Chemische 
Industrie.'' 

Pure  cryolite  contains — 

Aluminium .13.0 

Fluorine '.'.'..         .     54.5 

Sodium .         .     32.5 

100.00 

Or  otherwise  stated — 

Aluminium  fluoride  ......     40.25 

Sodium  fluoride 59.75 

100.00 

From  the  reports  in  the  Mineral  Resources  of  the  United 
States  we  find  that  there  was  imported  by  the  Pennsylvania  Salt 
Company  in  1887,  11,732  tons,  which  was  valued  at  nearly 
$15  a  ton.  The  importers  say  this  value  is  too  low;  they  sell 
what  they  call  pure  prepared  cryolite  at  $125  a  ton.  This  so 
called  pure  article  was  found  by  Prof.  Rogers,  of  Milwaukee,  to 
contain  2  per  cent,  of  silica  and  1  per  cent,  of  iron. 


OCCURRENCE   OF   ALUMINIUM   IN   NATURE.  51 

The  only  known  deposit  of  cryolite  in  the  United  States  is 
that  found  near  Pike's  Peak,  Colorado,  and  described  by  "W. 
Cross  and  W.  F.  Hillebrand  in  the  "American  Journal  of 
Science/'  October,  1883.  It  is  purely  of  mineralogical  import- 
ance and  interest,  occurring  in  small  masses  as  a  subordinate 
constituent  in  certain  quartz  and  feldspar  veins  in  a  country  rock 
of  coarse  reddish  granite.  Zircon,  astrophyllite,  and  columbite 
are  the  primary  associated  minerals,  the  first  only  being  abundant. 

CORUNDUM. 

Until  1869,  the  sole  sources  of  corundum  were  a  few  river 
washings  in  India  and  elsewhere,  where  it  was  found  in  scattered 
crystals.  Its  cost  was  twelve  to  twenty-five  cents  a  pound. 
Within  the  last  twenty  years  numerous  mines  have  been  opened 
in  the  eastern  United  States,  the  first  discovery  of  which  was 
due  to  Mr.  W.  P.  Thompson,  and  is  thus  described  by  him  :* 

"  In  1869,  in  riding  over  a  spur  of  the  Alleghenies  in  Northern 
Georgia,  I  found  what  has  proven  to  be  an  almost  inexhaustible 
mine  of  corundum  in  the  crysolite  serpentine,  the  first  instance 
on  record  of  the  mineral  being  found  in  situ.  Previously  it  had 
been  washed  out  of  debris  at  Cripp's  Hill,  N.  C.,  and  at  a 
mine  in  West  Chester,  Pa.,  both  on  the  slopes  of  the  crysolite  ser- 
pentine. The  clue  being  thus  obtained  accidentally,  about  thirty 
mines  were  shortly  afterwards  discovered  in  the  same  formation ; 
but  of  the  thousands  of  tons  thus  far  dug  out  the  larger  portion 
has  come  from  the  mines  I  discovered. 

"  At  present  it  can  be  bought  at  about  ten  dollars  per  ton  at 
the  mines.  It  is  nearly  pure  alumina.  Disapore,  a  hydrated 
aluminia,  is  also  found  in  the  same  region  and  locality.  Corun- 
dum will  probably  always  be  the  principal  source  in  America  of 
material  from  which  to  manufacture  pure  aluminiun ;  but  in 
Great  Britain,  in  all  probability,  manufacturers  must  look  to 
alumina  prepared  artificially  from  cryolite  or  from  sulphate  of 
alumina." 

In  1887,  the  production  of  corundum  in  the  United  States  was 

*  Journal  of  the  Society  of  Chemical  Industry,  April,  1886. 


52  ALUMINIUM. 

practically  limited  to  the  mines  of  the  Hampden  Emery  Company 
at  Laurel  Creek,  Ga.,  and  at  Corundum  Hill,  Macon  County, 
N.  C.,  these  mines  furnishing  somewhat  over  600  tons.  The 
Unionville  Corundum  Mines  Company  operate  a  mine  at  Union- 
ville,  Chester  County,  Pa.,  but  the  extent  of  their  output  is 
not  given. 

NATIVE  SULPHATE  OF  ALUMINA. 

In  the  summer  of  1884,  a  large  deposit  of  rock  called  "  native 
alum"  was  discovered  on  the  Gila  Eiver,  Sorocco  County,  New 
Mexico,  about  two  miles  below  the  fork  of  the  Little  Gila,  and 
four  miles  below  the  Gila  Hot  Springs.  The  deposit  is  said  to 
extend  over  an  area  one  mile  square  and  to  be  very  thick  in  places. 
The  greater  part  of  the  mineral  is  impure,  as  is  usual  with  native 
occurrences,  but  it  is  thought  that  large  quantities  are  available. 
A  company  formed  in  Sorocco  has  taken  up  the  alum-bearing 
ground.  Through  the  kindness  of  Mr.  W.  B.  Spear,  of  Phila- 
delphia, the  author  was  enabled  to  get  a  specimen  of  the  mineral. 

It  is  white,  with  a  yellowish  tinge.  On  examining  closely  it 
is  seen  to  consist  of  layers  of  white,  pure-looking  material  ar- 
ranged with  a  fibrous  appearance  at  right  angles  to  the  lamination. 
These  layers  are  about  one-quarter  of  an  inch  thick.  Separating 
them  are  thin  layers  of  a  material  which  is  deeper  yellow,  harder 
and  more  compact.  The  whole  lump  breaks  easily,  and  has  a 
strong  alum  taste.  On  investigation,  the  fibrous  material  was 
found  to  be  hydrated  sulphate  of  alumina,  the  harder  material 
sulphate  of  lime. 

It  is  probable  that  this  deposit  was  the  bed  of  a  shallow  lake 
in  which  the  alum-bearing  water  from  the  hot  springs  concentrated 
and  deposited  the  sulphate  of  alumina.  Periodically,  or  during 
freshets,  the  Little  Gila,  flowing  through  a  limestone  country, 
bore  into  this  lake  water  containing  lime,  which,  meeting  the 
aluminium  sulphate  solution,  immediately  caused  a  deposit  of 
calcium  sulphate.  When  the  dry  season  came,  the  Little  Gila 
dried  up,  the  deposit  of  alum  was  made,  and  thus  were  formed 
the  succession  of  layers  through  the  deposit. 

Analysis  showed  7  to  8  per  cent,  insoluble  material,  and  the 


PHYSICAL   PROPERTIES   OF   ALUMINIUM.  53 

remainder   corresponded   to   the  formula  A12(SO4)3.18H2O.      A 
small  amount  of  iron  was  present. 

[Further  information  about  some  of  the  native  aluminous 
minerals  has  unavoidably  fallen  into  the  chapter  describing 
aluminium  compounds.] 


CHAPTER  III. 

PHYSICAL   PROPERTIES    OF   ALUMINIUM. 

COMMERCIAL  aluminium  is  never  chemically  pure,  and  there- 
fore displays  properties  varying  more  or  less  from  those  of  the 
pure  metal  according  to  the  character  and  amount  of  impurities 
present.  In  this  treatise,  whenever  the  properties  of  aluminium 
are  mentioned  they  must  be  understood  to  refer  to  the  chemically 
pure  metal,  and  not  to  the  commercial  article  unless  specifically 
stated. 

The  impurities  most  frequently  present  in  commercial  alumin- 
ium are  iron  and  silicon.  These  are  found  in  all  brands,  varying 
in  amount  from  1  per  cent,  in  the  purest  to  6  and  even  8  per 
cent,  in  the  worst.  Besides  these,  various  other  impurities  are 
found  coming  from  accidental  sources  in  the  manufacture ;  thus, 
some  of  the  first  metal  made  by  Deville  contained  a  large  amount 
of  copper  (analysis  1),  coming  from  boats  of  that  metal  which  he 
used  in  his  experiments.  Metal  made  later  by  Deville  contained 
zinc,  coming  from  zinc  muffles  which  he  had  borrowed  and  used 
for  retorts,  old  retorts  broken  up  having  been  used  in  the  com- 
position of  the  new  ones.  More  recently,  aluminium  has  been 
produced  by  the  agency  of  sodium  in  the  presence  of  lead,  which 
latter  it  takes  up  in  small  amount.  Sodium  is  liable  to  remain 
alloyed  in  very  small  proportion,  yet  it  is  an  element  so  easily  at- 
tacked that  it  destroys  some  of  the  most  valuable  qualities  of  the 
aluminium.  The  distinct  effect,  however,  of  each  of  these  usual 
impurities  in  modifying  the  physical  properties  of  aluminium  has 
not  yet  been  investigated  in  a  thoroughly  satisfactory  manner. 


54 


ALUMINIUM. 


A  few  years  more,  however,  of  increasing  familiarity  with  and 
handling  of  the  metal  on  a  large  commercial  scale  will,  I  believe, 
cause  the  effect  of  foreign  elements  on  aluminium  to  be  as  plainly 
recognized  as  is  now  the  case  with  carbon  and  the  metalloids  in 
iron.  In  general,  we  may  say  that  silicon  seems  to  play  a  role  in 
aluminium  closely  analogous  to  that  of  carbon  in  iron  ;  the  purest 
aluminium  is  fibrous  and  tough,  but  a  small  percentage  of  silicon 
makes  it  crystalline  and  brittle.  Carbon,  moreover,  is  said  to  be 
dissolved  by  molten  aluminium  and  to  modify  its  properties 
quite  materially  ;  yet,  if  so,  almost  nothing  more  is  known  about 
its  influence  than  this  unsatisfactory  statement.  Here  is  excel- 
lent room  for  work  for  some  investigator  who,  as  Hampe  has 
done  with  copper,  will  prepare  the  purest  aluminium,  and  by 
adding  to  it  known  impurities  tell  us  precisely,  beyond  doubt,  how 
these  various  foreign  elements  affect  its  properties. 

The  following  analyses  will  show  the  amount  of  impurities  pres- 
ent in  commercial  aluminium,  and  also,  incidentally,  the  im- 
provement which  has  been  achieved  since  the  beginning  of  the 
industry  in  1854  :  — 


1.  Deville  Process          . 

2.  "  "  . 

3.  "  "  . 

4.  "  "  . 

5.  "  "  . 

6.  "  "  . 

7.  Tissier  Bros.  . 

8.  Moriii  &  Co.,  Nanterre 

9.  " 

10.  " 

11.  "  " 

12.  Merle  &  Co.,  Salindres 

13.  " 

14.  " 

15.  " 

16.  Frishmuth         .. 

17.  "  .. 

18.  Hall's  Process  .. 

19.  Deville-Castner          . 

20.  Grabau  Process          . 

21.  "  " 


Aluminium. 

Silicon. 

Iron. 

88.350 

2.87 

2.40 

92.500 

0.70 

6.80 

92.000 

0.45 

7.55 

92.969 

2.149 

4.88 

94.700 

3.70 

1.60 

96.160 

0.47 

3.37 

94.800 

0.80 

4.40 

97.200 

0.25 

2.40 

97.000 

2.70 

0.30 

98.290 

0.04 

1.67 

97.680 

0.12 

2.20 

96.253 

0.454 

3.293 

96.890 

1.270 

1.840 

97.400 

1.00 

1.30 

97.600 

0.40 

1.40 

97.49 

1.90 

0.61 

97.75 

1.70 

0.55 

98.34 

1.34 

0.32 

99.20 

0.50 

0.30 

99.62 

0.23 

0.15 

99.80 

0.12 

0.08 

PHYSICAL   PROPERTIES   OF    ALUMINIUM.  55 

Notes  on  the  above  analyses  : — 

1.  Analyzed  by  Salvetat.     Contained  also  6.38  per  cent,  of  copper  and  a 

trace  of  lead. 
2  and  6.  Analyzed  by  Dumas. 

3.  Parisian  aluminium  bought  in  La  Haag. 

4.  Analyzed  by  Salvetat.     Contained  also  a  trace  of  sodium. 

5.  Parisian  aluminium  bought  in  Bonn  and  analysed  by  Dr.  Kraut. 

7.  Made  at  the  works  near  Rouen,  in  18f»8,  from  cryolite.     Analyzed  by 

Demondeur. 

8.  Analyzed  by  Sauerwein.     Contained  also  traces  of  lead  and  sodium. 

9.  Analyzed  by  Morin.     Average  of  several  months'  work. 

10,  11.  Analyzed  by  Kraut.  Represents  the  best  product  of  the  French  works 
sent  to  the  London  Exhibition  in  1862. 

12,  13.  Analyzed  by  Mallet.  The  best  metal  which  could  be  bought  in  1880. 
Purchased  in  Berlin  by  Mallet  and  used  by  him  as  the  material  which 
he  purified  and  used  for  determining  the  atomic  weight  of  aluminium. 

14,  15.  Analyzed  by  Hampe.  This  was  the  purest  metal  which  could  be 
bought  in  1876.  No.  14  contained  also  0.10  per  cent,  of  copper  and 
0.20  per  cent,  of  lead.  No.  15  contained  0.40  per  cent,  of  copper  and 
0.20  per  cent,  of  lead. 

16.  Bought  in  Philadelphia  as  Frishmuth's  aluminium,  in  1885,  and  analyzed 

by  the  author. 

17.  Specimen  of  the  metal  composing  the  tip  of  the  Washington  Monument, 

cast  by  Frishmuth.     This  analysis  is  reported  by  R.  L.  Packard  in  the 
Mineral  Resources  of  the  United  States,  1883-4. 

18.  The  best  grade  of  metal  made  by  this  process,  analyzed  by  Hunt  &  Clapp, 

Pittsburgh.     For  average  analyses,  etc.,  see  description  of  process. 

19.  The  best  grade  made  by  this  process,  exhibited  at  the  Paris  Exposition, 

1889.     Analyzed  by  Cullen. 

20.  Analysis  by  Dr.  Kraut  of  metal  being  made  on  a  commercial  scale. 

21.  Analysis  by  Grabau  of  the  purest  metal  yet  obtained  by  his  process. 

According  to  Rammelsberg  (KerPs  Handbuch)  the  silicon 
which  is  always  found  in  aluminium  is  in  part  combined  with  it, 
and  this  combined  silicon  changes  by  treatment  with  hydrochloric 
acid  into  either  silica,  which  remains,  or  into  silicon  hydride, 
SiH4,  which  escapes ;  while  another  part  of  it  is  combined  with 
the  aluminium  just  as  graphite  is  with  iron;  and  this  part  re- 
mains on  treatment  with  acid  as  a  black  mass  not  oxidized  by 
ignition  in  the  air.  Two  analyses  of  aluminium  reduced  from 
cryolite  by  sodium  in  a  porcelain  crucible  gave — 

i.  2. 

Silicon  obtained  as  silica    ....     9.55  1.85 

Free  silicon 0.17  0.12 

Silicon  escaping  in  SiH4      ....     0.74  0.58 


56  ALUMINIUM. 

One  sample  of  aluminium  analyzed  by  Professor  Rammelsberg 
contained  as  much  as  10.46  per  cent,  of  silicon,  and  another 
sample  even  13.9  per  cent.  The  quantity  of  iron  varied  from 
2.9  to  7.5  per  cent. 

M.  Dumas  found  that  aluminium  usually  contains  gases,  about 
which  he  makes  the  following  statements  :*  On  submitting  alu- 
minium in  a  vacuum  to  the  action  of  a  gradually  increasing  tem- 
perature up  to  the  softening  point  of  porcelain,  and  letting  the 
mercury  pump  continue  acting  on  the  retort  until  it  was  com- 
pletely exhausted,  considerable  quantities  of  gas  were  withdrawn. 
The  liberation  of  the  gas  from  the  metal  seems  to  take  place  sud- 
denly towards  a  red-white  heat.  200  grammes  of  aluminium,  oc- 
cupying 80  c.c.,  gave  89.5  c.c.  of  gas,  measured  at  17°  and  755 
mm.  pressure.  The  gas  consisted  of  1.5  c.c.  carbonic  acid,  and 
88  c.c.  hydrogen.  Carbonic  oxide,  nitrogen  and  oxygen  were 
absent. 

The  author  has  observed  that  molten  aluminium  will  absorb 
large  quantities  of  gas.  On  passing  sulphuretted  hydrogen  into 
the  melted  metal  for  about  twenty  minutes  some  aluminium  sul- 
phide was  formed  while  the  metal  appeared  to  absorb  the  gas. 
On  pouring,  the  metal  ran  very  sluggishly  with  a  thick  edge,  but 
when  just  on  the  point  of  setting  gas  was  disengaged  so  actively 
that  the  crackling  sound  could  be  heard  several  feet  away,  and 
the  thick  metal  became  suddenly  quite  fluid  and  spread  over  the 
plate  in  a  thin  sheet.  The  gas  disengaged  seemed  by  its  odor  to 
contain  a  good  proportion  of  sulphuretted  hydrogen,  although 
free  hydrogen  may  have  been  present  in  it. 

COLOR. 

Deville  :  The  color  of  aluminium  is  a  beautiful  white  with  a 
slight  blue  tint,  especially  when  it  has  been  strongly  worked. 
Being  put  alongside  silver,  their  color  is  sensibly  the  same. 
However,  common  silver,  and  especially  that  alloyed  with  copper, 
has  a  yellow  tinge,  making  the  aluminium  look  whiter  by  com- 
parison. Tin  is  still  yellower  than  silver,  so  that  aluminium  pos- 
sesses a  color  unlike  any  other  useful  metal. 

*  Comptes  Rendue  xc.  1027  (1880). 


PHYSICAL   PROPERTIES   OF   ALUMINIUM.  57 

Mallet :  Absolutely  pure  aluminium  is  perceptibly  whiter  than 
the  commercial  metal ;  on  a  cut  surface  very  nearly  pure  tin- 
white,  without  bluish  tinge,  as  far  as  could  be  judged  from  the 
small  pieces  examined. 

The  purest  aluminium  examined  by  the  author  is  that  made 
by  Grabau.  On  a  fresh  fracture  it  is  absolutely  white,  but  on 
long  exposure  to  the  air  it  takes  a  faint,  almost  imperceptible 
bluish  tint.  On  a  cut  surface  it  has  the  faintest  suspicion  of  a 
yellow  tint,  not  so  decided  as  the  yellowish  color  of  pure  tin. 
Ordinary  commercial  aluminium  is  bluish  on  a  fresh  fracture, 
the  tint  being  deeper  the  greater  the  amount  of  impurities  it  con- 
tains. A  specimen  with  10  per  cent,  of  silicon  and  5  per  cent,  of 
iron  was  almost  as  blue  as  lead.  It  is  my  belief  that  a  very  small 
percentage  of  copper  closes  the  grain  and  whitens  the  fracture  a 
little ;  I  have  also  found  that  chilling  suddenly  from  a  high  tem- 
perature has  the  same  effect.  When  ingots  of  aluminium  are  ex- 
posed a  long  time  to  damp  air  the  thin  film  of  oxide  forming  011 
them  gives  a  more  decided  bluish  cast  to  the  metal,  since  the 
coating  is  perfectly  snow-white  and  hence,  by  contrast,  heightens 
the  bluish  tint  of  the  metallic  back-ground.  Mourey  recom- 
mended removing  this  discoloration  by  placing  the  articles  first 
in  dilute  hydro-fluoric  acid,  1000  parts  of  water  to  2  of  acid,  and 
afterwards  dipping  in  nitric  acid.  The  oxide  would  thus  be 
dissolved  and  the  original  color  restored.  Pure  aluminium  pos- 
sesses to  the  highest  degree  that  property  expressed  best  by  the 
French  term  "  eclat."  It  is  rather  difficult  to  see  why  the  blue 
tint  should  be  more  prominent  after  the  metal  has  been  worked, 
yet  I  think  two  reasons  will  explain  this  phenomenon ;  first,  alu- 
minium is  not  a  hard  metal,  and  on  polishing  or  burnishing  par- 
ticles of  dirt  or  foreign  substances  are  driven  into  the  pores  of  the 
metal,  thereby  altering  its  color  slightly ;  second,  any  metal  looks 
whiter  when  its  surface  is  slightly  rough  than  when  highly  pol- 
ished, in  the  latter  case  it  being  as  much  the  reflected  color  of  the 
general  surroundings  as  the  color  of  the  metal  itself  which  is  seen. 
I  have  never  seen  any  highly  polished  white  metal  which  did  not 
look  bluish  especially  when  reflecting  out-door  light.  I  think 
this  explains  why  opera  glasses,  rings,  jewelry,  etc.,  generally  look 
bluer  than  the  bar  or  ingot-metal  from  which  they  are  made. 


58  ALUMINIUM. 

Aluminium  takes  a  very  beautiful  mat  which  keeps  almost  in- 
definitely in  the  air,  the  surface  thus  slightly  roughened  appear- 
ing much  whiter  than  the  original  polished  surface.  Aluminium 
can  be  polished  and  burnished  without  much  difficulty  if  attention 
is  given  to  a  few  particulars  which  it  is  necessary  to  observe. 
(For  methods  of  polishing,  etc.,  see  Chapter  XIII.) 

FRACTURE. 

A  cast  ingot  of  purest  aluminium  has  a  slightly  fibrous  struct- 
ure, a  section  J  inch  thick  bending  twenty  degrees  or  so  from  a 
straight  line  when  sharply  bent  before  showing  cracks  at  the 
outside  of  the  turn.  The  fracture  of  such  an  ingot  is  uneven, 
rough,  and  very  close,  often  showing  a  curious  semi-fused  appear- 
ance, as  if  it  had  been  already  exposed  to  heat  and  the  sharpest 
j joints  melted  down.  However,  only  the  purest  varieties  show 
these  peculiarities.  Metal  containing  96  to  97  per  cent,  of 
aluminium  begins  to  show  a  crystalline  structure,  breaks  short, 
and  with  a  tolerably  level  surface.  Metal  less  than  95  per 
cent,  pure  shows  large  shining  crystal  surfaces  on  the  fracture, 
the  smaller  crystals  being  on  the  outside  of  the  ingot  where  it  has 
been  cooled  most  quickly,  while  in  the  centre  the  crystalline  sur- 
faces may  be  as  large  as  y1^  inch  in  diameter.  A  specimen  con- 
taining only  85  per  cent,  of  aluminium  broke  as  short  as  a  bar  of 
autimonial  lead,  with  a  large  granular,  crystalline  surface. 

Working  the  metal  increases  its  fibrousness  greatly,  the  section 
of  a  square  rolled  bar  of  good  metal  looking  very  much  like 
that  of  a  low-carbon  steel. 

HARDNESS. 

The  purest  aluminium  is  distinctly  softer  than  the  commercial, 
estimated  on  the  scale  of  hardness  proposed  by  Mohs  it  would 
be  written  as  about  2.5,  that  is,  a  little  harder  than  can  be 
scratched  by  the  nail.  It  is  not  so  soft  as  pure  tin.  The  presence 
of  impurities,  however,  rapidly  increases  the  hardness.  While 
99  per  cent,  aluminium  can  be  cut  smoothly  with  the  knife  and 
shavings  turned  up  almost  as  with  pure  tin,  yet  95  per  cent,  metal 


PHYSICAL   PROPERTIES   OF   ALUMINIUM.  59 

can  hardly  be  cut  at  all,  the  shavings  break  off  short  and  a  fine 
grating  is  felt  through  the  blade. 

Experience  in  testing  various  specimens  of  commercial  alumin- 
ium with  the  knife  will,  I  am  sure,  enable  a  person  to  become 
quite  skilful  in  determining  the  purity  and  in  separating  different 
grades  from  each  other.  Taking  this  test  in  connection  with  the 
breaking  and  surface  of  fracture,  it  appears  to  me  that  these 
indications  are  as  significant  and  can  be  made  of  as  much  use  as 
the  corresponding  tests  for  iron,  steel,  and  other  metals.  Mr. 
Joseph  Richards,  the  author's  father,  having  had  many  years' 
experience  in  testing  lead,  tin,  zinc,  and  similar  metals,  in  which 
the  knife  blade  has  been  put  to  good  service,  has  been  able  with 
very  little  practice  to  arrange  a  number  of  specimens  of  alumin- 
ium correctly  according  to  their  purity  simply  by  noting  care- 
fully the  way  they  cut  and  the  color  of  the  cut  surface.  These 
tests  will  in  the  future,  I  am  sure,  be  of  great  use  to  those  hand- 
ling aluminium  on  a  large  scale,  especially  in  the  works  where 
it  is  produced. 

Aluminium  becomes  sensibly  harder  after  being  worked,  prob- 
ably owing  to  the  closing  of  the  grain,  since  we  know  that  its 
density  is  also  increased. 

SPECIFIC  GRAVITY. 

Mallet :  The  specific  gravity  of  absolutely  pure  aluminium 
was  carefully  determined  at  4°  C.,  and  the  mean  of  three  closely 
agreeing  observations  gave  2.583. 

Commercial  aluminium  is  almost  always  heavier  than  this, 
but  the  increase  is  not  in  direct  proportion  to  the  amount  of  im- 
purities present.  There  are  two  reasons  why  this  last  statement 
is  correct;  first,  we  cannot  say  what  expansion  or  contraction 
may  take  place  in  forming  the  alloy ;  second,  while  most  of  the 
impurities  which  occur  are  much  heavier  than  aluminium,  yet 
silicon,  the  most  frequent  of  all,  has  a  specific  gravity  of  only 
2.34  (Deville's  determination),  and  therefore  acts  in  the  opposite 
direction  to  the  other  impurities,  though  not  to  as  great  an  extent. 
The  following  analyses  and  specific  gravities  may  give  some  in- 
formation on  this  point : — 


60  ALUMINIUM. 


SPECIFIC  GRAVITY. 


Aluminium.  Silicon.  Iron.  Observed.  Calculated. 

97.60           0.60  1.80                        2.735  2.61  (2.64) 

95.93           2.01  2.06                         2.800  2.61  (2.69) 

94.16           4.36  1.48                        2.754  2.59  (2.74) 

78.—  16.—  4.—                       2.85  2.66 

It  is  seen  in  each  case  that  the  calculated  specific  gravity  is 
much  less  than  the  observed,  which  would  show  contraction  in 
volume  by  alloying.  Indeed,  this  is  a  prominent  characteristic 
of  aluminium  alloys,  aluminium  often  taking  up  several  per  cent, 
of  its  weight  of  another  metal  without  its  volume  being  increased, 
the  particles  of  the  other  metal  seeming  to  pass  between  those  of 
the  aluminium ;  thus  probably  accounting  for  the  extraordinary 
strength  and  closeness  of  many  of  the  aluminium  alloys.  This 
subject  is  treated  more  at  length  in  the  chapter  on  alloys.  We  can 
see  the  large  contraction  taking  place  by  inspecting  the  numbers 
in  parentheses  under  the  heading  "Calculated."  These  are 
computed  on  the  supposition  that  the  volume  of  the  impure  alu- 
minium is  equal  to  that  of  the  pure  aluminium  entering  into  it. 
As  these  numbers  are  also  less  than  the  observed  specific  gravi- 
ties, the  extraordinary  fact  is  shown  that  aluminium  can  absorb 
several  per  cent,  of  iron  and  silicon  and  yet  will  decrease  in 
volume  in  doing  so. 

The  remarks  thus  far  made  are  based  on  the  gravity  of  cast 
metal.  Aluminium  increases  in  density  by  being  worked  ;  De- 
ville  states  that  metal  with  a  specific  gravity  of  2.56  had  this 
increased  to  2.67  by  rolling,  which,  he  says,  may  explain  the 
differences  existing  in  its  properties  after  being  annealed  or 
worked.  He  remarked  further  that  heating  this  rolled  metal  to 
100°,  and  cooling  quickly  changed  its  specific  gravity  very  little, 
lowering  it  to  2.65.  I  have  observed  that  on  heating  a  piece  of 
aluminium  almost  to  its  fusing  point  and  suddenly  chilling  it  in 
water,  its  specific  gravity  was  lowered  from  2.73  to  2.69. 

The  low  specific  gravity  of  aluminium,  when  compared  to  those 
of  the  other  metals,  is  (in  the  words  of  a  recent  lecturer)  "  the 
physical  property  on  which  our  hopes  of  the  future  usefulness  of 
aluminium  chiefly  rest."  The  following  table  will  facilitate  this 
comparison : — 


PHYSICAL   PROPERTIES   OF   ALUMINIUM.  61 

SPECIFIC  GRAVITY. 


Water  =  1.       Alumin-     Pounds  in  a      Kilos  in  a 
iuin  =  1.      cubic  foot,      cubic  meter. 


Platinum 

.     21.5 

8.3 

1344 

21,500 

Gold 

.     19.3 

7.4 

1206 

19,300 

Lead 

.     11.4 

4.6 

712 

11,400 

Silver     . 

.     10.5 

4.0 

656 

10,500 

Copper  . 

.       8.9 

3.5 

557 

8,900 

Iron  and  steel 

.      7.8 

2.8 

487 

7,800 

Tin 

7.3 

2.7 

456 

7,300 

Zinc 

.      7.1 

2.7 

444 

7,100 

Aluminium    . 

.       2.6 

1.0 

163 

2,600 

In  comparing  the  price  of  aluminium  with  that  of  the  metal 
it  is  to  replace,  for  such  purposes  where  the  bulk  of  the  article  is 
fixed,  such  as  tableware,  jewelry,  engineering  instruments,  and  a 
large  proportion  of  all  its  uses,  it  is  important  to  take  its  low 
specific  gravity  into  the  account.  Thus,  for  making  spoons,  alu- 
minium at  $4  per  Ib.  would  be  as  cheap  as  silver  at  $1  per  lb., 
since  the  silver  spoons  would  be  four  times  as  heavy.  So  for 
such  purposes,  at  the  prices  prevailing  to-day,  aluminium  is 
practically  only  one-tweuty-fifth  as  costly  as  silver. 

FUSIBILITY. 

Deville :  Aluminium  melts  at  a  temperature  higher  than  that 
of  zinc,  lower  than  that  of  silver,  but  approaching  nearer  to  that 
of  zinc  than  silver.  It  is,  therefore,  quite  a  fusible  metal. 

Mallet :  It  seems  that  pure  aluminium  is  a  little  less  fusible 
than  the  commercial  metal. 

Picktet  determined  the  melting  point  to  be  600°,  Heeren 
about  700°,  while  Van  der  Weyde  placed  it  as  high  as  850°.* 
Prof.  Carnelley  has  lately  determined  this  point  himself,  and 
found  that  a  sample  containing  J  per  cent,  of  iron  melted  at 
700°,  while  one  with  5  per  cent,  of  iron  did  not  fuse  completely 
until  above  730°.  These  numbers  can  be  accepted  as  the  best 
determinations  yet  made,  and  it  results  from  them  that  iron 
raises  the  melting  point  and  hinders  fluid  fusion.  Since  it  is 
already  conceded  that  silicon  raises  the  melting  point  until,  with 

*  Carnelley's  Tables  of  Melting  Points. 


62  ALUMINIUM. 

a  large  percentage,  the  metal  can  hardly  be  made  fluid  at  any 
heat,  it  is  rather  puzzling  to  see  why  the  absolutely  pure  metal 
should  be  less  fusible  than  the  commercial  metal,  as  is  remarked 
by  Mallet.  It  may  be  that  the  small  percentages  of  iron  and 
silicon  present  in  a  high  grade  of  commercial  metal  act  in  a  man- 
ner contrary  to  the  effect  of  larger  percentages,  as  is  known  to  be 
true  in  a  few  instances  with  the  impurities  present  in  other 
metals,  but  we  have  no  definite  information  to  bring  forward  on 
this  point. 

VOLATILIZATION. 

Deville :  Aluminium  is  absolutely  fixed,  and  loses  no  part  of 
its  weight  when  it  is  violently  heated  in  a  forge  fire  in  a  carbon 
crucible. 

This  statement  was  made  in  1859,  and  can  still  be  accepted  as 
true  as  far  as  ordinary  furnace  temperatures  are  concerned.  But, 
with  the  use  of  the  electric  furnace,  temperatures  have  been  at- 
tained at  which  aluminium  does  sensibly  volatilize.  In  Cowles 
Bros,  electric  furnace  it  is  stated  that  the  aluminium  is  almost  all 
produced  as  vapor  and  as  such  is  absorbed  by  the  copper  or  iron 
present,  when  these  are  not  present  it  is  found  condensed  in  the 
cooler  upper-part  of  the  furnace.  A  similar  experience  has  been 
met  in  other  electric  furnace  processes,  so  that  the  volatilization 
of  aluminium  at  these  extreme  temperatures  may  be  accepted  as 
a  fact. 

ODOR. 

Deville :  The  odor  of  pure  aluminium  is  sensibly  nothing,  but 
the  metal  strongly  charged  with  silicon  will  exhale  the  odor  of 
silicuretted  hydrogen,  exactly  represented  by  the  odor  of  cast 
iron.  But  even  under  these  unfavorable  circumstances,  the  smell 
of  the  metal  is  only  appreciable  to  persons  experienced  in  judging 
very  slight  sensations  of  this  kind. 

TASTE. 

Deville :  Pure  aluminium  has  no  taste,  but  the  impure  and 
odorous  metal  may  have  a  taste  like  iron,  in  any  case  only  very 
slight. 


PHYSICAL  PROPERTIES  OF  ALUMINIUM.  63 

MAGNETISM. 

Deville :  I  have  found,  as  also  MM.  Poggendorff  and  Reiss, 
that  aluminium  is  very  feebly  magnetic. 

SONOROUSNESS. 

Deville  :  A  very  curious  property,  which  aluminium  shows  the 
more  the  purer  it  is,  is  its  excessive  sonorousness,  so  that  a  bar  of 
it  suspended  by  a  fine  wire  and  struck  sounds  like  a  crystal  bell. 
M.  Lissajous,  who  with  me  observed  this  property,  has  taken  ad- 
vantage of  it  to  construct  tuning  forks  of  aluminium,  which  vi- 
brate very  well.  I  also  tried  to  cast  a  bell,  which  has  been  sent 
to  the  Royal  Institution  at  London  at  the  request  of  my  friend 
Rev.  J.  Barlow,  vice-president  and  secretary  of  the  institution. 
This  bell,  cast  on  a  model  not  well  adapted  to  the  qualities  of  the 
metal,  gives  a  sharp  sound  of  considerable  intensity,  but  which  is 
not  prolonged,  as  if  the  clapper  or  support  hindered  the  sound, 
which,  thus  hindered,  becomes  far  from  agreeable.  The  sound 
produced  by  the  ingots  is,  on  the  contrary,  very  pure  and  pro- 
longed. In  the  experiments  made  in  Mr.  Faraday's  laboratory, 
this  celebrated  physicist  has  remarked  that  the  sound  produced 
by  an  ingot  of  aluminium  is  not  simple.  One  can  distinguish,  by 
turning  the  vibrating  ingot,  two  sounds  very  near  together  and 
succeeding  each  other  rapidly,  according  as  one  or  the  other  face 
of  the  ingot  faces  the  observer. 

The  bell  referred  to  above  was  20  kilos  in  weight  and  50  centi- 
metres in  diameter,  but  as  Deville  admits,  its  sound  was  not 
pleasing,  and  a  contemporary  writer,  evidently  not  very  enthusi- 
astic in  sounding  the  praises  of  aluminium,  said  that  while  the 
bell  was  highly  sonorous  yet  it  "  gave  a  sound  like  a  cracked 
pot." 

I  have  not  heard  that  any  large  bell  has  since  been  cast,  but  it 
is  certain  that  the  metal  in  bars  has  a  highly  musical  ring. 
Faraday's  observation  has  also  been  verified,  for  a  recent  lecturer 
suspended  by  one  end  a  bar  6  feet  long,  3J  inches  wide,  and  1J 
inches  thick,  and  on  striking  it  a  prolonged  vibration  ensued,  two 


64  ALUMINIUM. 

notes  being  recognized,  A  sharp  and  D  sharp,  the  latter  more 
subdued. 

CRYSTALLINE  FORM. 

Deville :  Aluminium  often  presents  a  crystalline  appearance 
when  it  has  been  cooled  slowly.  When  it  is  not  pure  the  little 
crystals  which  form  are  needles,  and  cross  each  other  in  all 
directions.  When  it  is  almost  pure  it  still  crystallizes  by  fusion 
but  with  difficulty,  and  one  may  observe  on  the  surface  of  the 
ingots  hexagons  which  appear  regularly  parallel  along  lines  which 
centre  in  the  middle  of  the  polygon.  It  is  an  error  to  conclude 
from  this  observation  that  the  metal  crystallizes  in  the  rhombo- 
hedral  system.  It  is  evident  that  a  crystal  of  the  regular  system 
may  present  a  hexagonal  section  ;  while  on  the  other  hand,  in 
preparing  aluminium  by  the  battery  at  a  low  temperature,  I 
have  observed  complete  octahedrons  which  were  impossible  of 
measurement  it  is  true,  but  their  angles  appeared  equal. 

ELASTICITY. 

Deville  :  M.  Wertheim  has  found  that  the  elasticity  of  alumin- 
ium just  cast  is  sensibly  the  same  as  that  of  silver;  but  when 
worked  it  resembles  that  of  soft  iron,  becoming  more  rigid  and 
elastic,  and  giving  the  sound  of  steel  when  dropped  on  a  hard 
body. 

Mallet  remarked  that  absolutely  pure  aluminium  seemed  to  be 
less  hardened  by  hammering  than  ordinary  commercial  metal. 
A  German  firm  engaged  in  making  aluminium  state  that  by 
long,  gradual  cooling  from  a  red  heat  aluminium  can  be  made 
so  elastic  that  it  can  even  be  used  for  hair  springs  for  watches. 
Annealing  by  cooling  quickly  from  a  red  heat  makes  the  metal 
soft.  Aluminium  stiffens  up  very  quickly  in  rolling;  the  author's 
father  has  found  the  best  means  of  removing  this  is  to  heat  the 
metal  red  hot  and  plunge  into  water.  Metal  thus  treated  becomes 
very  soft.  Fine  wire  quickly  becomes  hard  in  drawing,  but  can 
be  annealed  in  the  heat  over  an  argand  burner. 


PHYSICAL  PKOPERTIES  OF  ALUMINIUM.  65 

TENACITY. 

"VV.  H.  Barlow  :*  A  bar  of  aluminium  three  feet  long  and  one- 
quarter  inch  square  was  obtained  and  different  parts  of  it  sub- 
jected to  tests  for  tension,  compression,  and  transverse  strain, 
elasticity,  elastic  range,  and  ductility.  It  will  be  seen  on  refer- 
ence to  the  results  that  the  weight  of  a  cubic  inch  was  0.0275 
pound,  showing  a  specific  gravity  of  2.688,  and  its  ultimate  ten- 
sile strength  was  about  twelve  tons  per  square  inch.  The  range 
of  elasticity  is  large,  the  extreme  to  the  yielding  point  being 
one-two  hundredths  of  the  length.  The  modulus  of  elasticity  is 
1,000,000,  the  extension  in  samples  two  inches  long  being  2.5 
per  cent.  Taking  the  tensile  strength  of  the  metal  in  relation 
to  its  weight,  it  shows  a  high  mechanical  value.  These  results 
are  thus  tabulated  : — 


Weight  of 

Teusile 

Length  of  a 

1  cubic  foot 

strength 

bar  able  to  sup- 

iu pounds. 

per  sq.in. 

port  its  weight, 

in  pounds. 

in  feet. 

Cast  iron 

.     444 

16.500 

5,351 

Bronze 

.     525 

36,000 

9,893 

Wrought  iron 

.     480 

50,000 

15,000 

Steel     . 

.     490 

78,000 

23,040 

Aluminium 

.     1H8 

26,800 

23,040 

It  thus  appears  that  taking  the  strength  of  aluminium  in  rela- 
tion to  its  weight,  it  possesses  a  mechanical  value  about  equal  to 
that  of  steel  of  35  tons  per  square  inch  tensile  strength. 

Kamarscht  obtained  the  following  results  as  to  the  strength 
of  aluminium  wire  : — 

DIAMETER.  TENSILE  STKKNHTH,  GRAMMFS.  TENACITY. 

Kilos  per  sq.  millimetre. 
12.975 
12.255 
12.700 
11.845 

These  results  are  far  below  that  obtained  by  Barlow,  which  is 
equal  to  18.92  kilos  per  square  millimetre.  The  latter  figure  is, 

*  Rpt.  Brit.  A.  A.  S.,  1882,  p.  668. 
f  Dingier,  172,  p.  55. 


illimetres. 

1st  trial. 

2d  trial. 

Meau. 

0.225 

661 

653 

657 

0.205 

524 

506 

515 

0.160 

307 

311 

309 

0.145 

246 

252 

249 

66  .  ALUMINIUM. 

however,  undoubtedly  nearer  the  truth  for  good  aluminium,  since 
tests  of  the  metal  made  by  the  Deville-Castner  process  average 
25,000  to  30,000  Ibs.  per  square  inch,  being  in  general  higher 
than  the  figure  given  by  Barlow. 

MALLEABILITY. 

Deville :  Aluminium  may  be  forged  or  rolled  with  as  much 
perfection  as  gold  or  silver.  It  is  beaten  into  leaves  as  easily  as 
they,  and  a  very  experienced  gold-beater,  M.  Rousseau,  has  made 
leaves  as  fine  as  those  of  gold  or  silver,  which  are  put  up  in 
books.  I  know  of  no  other  useful  metal  able  to  stand  this  treat- 
ment. 

Mallet :  With  absolutely  pure  aluminium  the  malleability  was 
undoubtedly  improved,  the  metal  yielding  easily  to  the  hammer, 
bearing  distortion  well,  and  flattening  in  two  or  three  directions 
without  cracking.  It  seemed  to  be  sensibly  less  hardened  by 
hammering  than  the  ordinary  metal  of  commerce. 

Commercial  aluminium  is  now  to  be  had  rolled  into  sheets  of 
almost  any  size  or  thickness,  and  at  only  a  small  advance  on  the 
price  of  ingot  metal.  The  only  particulars  in  which  it  differs 
much  from  other  metals  being  that  it  must  be  annealed  much 
oftener,  and  requires  an  extraordinarily  large  power  to  roll  it. 
Mr.  J.  Richards  compares  the  cold  rolling  of  aluminium  to  the 
hot  rolling  of  steel  in  regard  to  the  power  required  ;  he  also  finds 
that  unless  the  sheet  is  rolled  until  quite  hard  it  does  not  polish 
in  the  rolls. 

The  aluminium  leaf  is  now  in  regular  use  with  gilders  and 
decorators.  It  was  first  made  by  M.  Degousse,  of  Paris,  and 
afterwards  for  several  years  by  C.  Falk  &  Co.,  of  Vienna.  The 
manufacture  is  rather  more  difficult  than  beating  out  gold  or 
silver,  and  requires  also  a  pure  metal  to  stand  the  working.  A 
specimen  such  as  is  sold  commercially  was  measured  by  the 
author.  He  found  its  thickness  to  be  0.000,638  millimetres  or 
one-forty  thousandth  of  an  inch,  which  compares  favorably  with 
that  of  ordinary  gold  leaf.  It  is  quite  possible  that  if  a  test  were 
made  with  extra  pure  metal,  this  result  would  easily  be  exceeded. 


PHYSICAL   PROPERTIES    OF   ALUMINIUM.  67 

This  leaf  was  not  thin  enough  to  show  any  color  by  transmitted 
light. 

Deville  has  stated  that  aluminium  can  be  forged  with  as  much 
perfection  as  gold  or  silver,  but  at  what  heat  it  works  best  is  not 
stated.  It  can  readily  be  hammered  and  shaped  cold,  like  silver 
or  copper,  but  it  soon  stiffens  up,  and  must  be  kept  soft  by  fre- 
quent annealing. 

Aluminium  probably  stands  third  in  the  order  of  malleability 
of  the  metals,  gold  and  silver  exceeding  it ;  while  it  is  probably 
sixth  in  the  order  of  ductility,  being  preceded  by  gold,  silver, 
platinum,  iron,  and  copper.* 

DUCTILITY. 

Deville :  Aluminium  behaves  very  well  at  the  drawing  plate. 
M.  Vangeois  obtained,  in  1855,  with  a  metal  far  from  being  pure, 
wires  of  extreme  tenuity,  which  were  used  to  make  aluminium 
passementerie.  However,  the  metal  deteriorates  much  in  the 
operation,  and  the  threads  become  flexible  again  only  after  an 
annealing  very  delicately  performed,  because  of  the  fineness  of 
the  threads  and  the  fusibility  of  the  metal.  The  heat  of  the  air 
coming  from  the  top  of  the  chimney  over  an  Argand  burner  is 
sufficient  to  anneal  them. 

Aluminium  wire  is  being  made  at  present  by  numbers  of 
manufacturers,  the  difficulties  being  very  few  when  pure  metal 
can  be  procured  to  work  with.  Quite  a  large  amount  of  power 
is  required  for  drawing  when  compared  with  other  metals.  Wire 
as  fine  as  0.1  millimetre  in  diameter  can  be  made  without  very 
much  trouble,  and  the  use  of  aluminium  in  this  form  promises 
large  development  in  the  near  future. 

EXPANSION  BY  HEAT. 

Fizeau  is  quoted  as  authority  for  the  following  coefficients  of 
linear  expansion  of  aluminium  by  heat : — 

For  1°  F.  For  1°  C. 

Cast  aluminium    ....     0.00001234  0.00002221 

Crystallized  aluminium         .         .     0.00000627  0.00001129 


*  Thurston's  Materials  of  Engineering. 


68  ALUMINIUM. 

SPECIFIC  HEAT. 

Deville :  According  to  the  experiments  of  M.  Regnault,  the 
specific  heat  of  aluminium  corresponds  to  its  equivalent  13.75, 
from  which  we  may  conclude  that  it  must  be  very  large  when  com- 
pared with  all  the  other  useful  metals.  One  can  easily  perceive 
this  curious  property  by  the  considerable  time  which  it  takes  an 
ingot  of  the  metal  to  get  cold.  We  might  even  suggest  that  a 
plate  of  aluminium  would  make  a  good  chafing-dish.  Another 
experiment  makes  this  conclusion  very  evident.  M.  Paul  Morin 
had  the  idea  of  using  aluminium  for  a  plate  on  which  to  cook  eggs, 
the  sulphur  of  which  attacked  silver  so  easily ;  and  he  obtained 
excellent  results.  He  noticed,  also,  that  the  plate  kept  its  heat  a 
much  longer  time  than  the  silver  one. 

The  value  of  this  quantity  has  been  quoted  differently  by 
different  authorities.  Regnault  obtained  0.2143  as  the  mean 
between  0°  and  100°,  while  Kopp  obtained  0.2020.  In  the  first 
case  Deville  remarks  that  the  metal  he  gave  Regnault  was  unfor- 
tunately contaminated  with  copper,  which  would  lead  to  the  sup- 
position that  the  value  obtained  was  somewhat  below  the  truth  ; 
we  cannot  account  for  the  lower  value  obtained  by  Kopp.  How- 
ever these  may  be,  more  recent  and  probably  more  accurate 
determinations  have  indicated  a  higher  value.  Mallet  deter- 
mined the  specific  heat  of  absolutely  pure  aluminium  to  be 
0.2253,  which,  he  remarked,  made  its  atomic  heat  0.2253  X  27.02 
or  6.09.  Naccari*  observed  the  specific  heat  at  different  tem- 
peratures to  be — 

18°  50°  100°  200°  300° 

0.2135  02.164  0.2211  0.2306  0.2401 

The  author  has  determined  the  mean  specific  heat  from  0°  to 
the  melting  point  to  be  02.85,  and  the  latent  heat  of  fusion  29.5 
calories. 

ELECTRIC  CONDUCTIVITY. 

Deville :  Aluminium  conducts  electricity  with  great  facility, 
so  that  it  may  be  considered  as  one  of  the  best  conductors  known, 

*  Transactions  "Accademia  di  Torino,"  Dec.  1887. 


PHYSICAL    PROPERTIES   OF   ALUMINIUM.  69 

and  perhaps  equal  to  silver.  I  found  by  Wheatstone's  Bridge 
that  it  conducts  eight  times  better  than  iron.  M.  Buff  has 
arrived  at  results  evidently  different  from  mine  because  we  have 
not  taken  the  same  ground  of  comparison.  The  difference  is  due, 
without  doubt,  to  the  metal  which  he  employed  containing,  as  is 
easily  found  in  many  specimens,  a  little  cryolite  and  fusible 
materials  the  density  of  which  is  near  that  of  the  metal,  and 
which  were  employed  in  producing  it.  The  complete  separation 
of  the  metal  and  flux  is  a  difficult  mechanical  operation,  but 
which  is  altogether  avoided  by  using  a  volatile  flux.  This  is  a 
condition  which  must  be  submitted  to  in  order  to  get  the  metal 
absolutely  pure. 

The  exact  value  expressing  the  electric  conductivity  of  alumin- 
ium is  not  beyond  dispute.  In  one  place  we  find  the  following 
relative  numbers  given  : — * 

At  0°  At  100° 

Copper          .         .         .         .  .      .         .     45.74  33.82 

Magnesium 24.47  17.50 

Aluminium 22.46  17.31 

M.  Margottet  states  it  as  being  51.5  if  copper  is  100;  or  33.74 
silver  being  100.  Professor  Mattheisen  determined  the  values  as 
follows  : — 

Pure  silver 100 

Commercial  copper       .......       77 

Commercial  aluminium        ......       33.76 

Watts  states  that  the  electric  conductivity  of  aluminium  is 
56.1  silver  being  100.  Finally,  Benoitf  gives  the  mean  electric 
resistance  and  conductivity  at  0°  as  follows,  the  resistance  being 
for  a  wire  1  metre  long,  and  with  a  cross  section  of  0.2  square 
centimetres  (a  column  of  mercury  of  those  dimensions  giving 
resistances  of  0.9564  Ohms  or  1.0  Siemens). 


Ohms. 

Siemens.      Conductivity. 

Silver,  annealed 

.     0.0154 

0.0161 

100 

Copper,        " 

.     0.0171 

0.0179 

90 

Gold,            "                 . 

.     0.0217 

0.0227 

71 

Aluminium,  annealed 

.     0.0309 

0.0324 

49.7 

Magnesium,  hard 

.     0.0423 

0.0443 

36.4 

*  Jahresb.  der  Chemie,  1881,  p.  94. 
f  Thurston's  Materials  of  Engineering. 


70  ALUMINIUM. 

If  we  compare  these  various  results  we  find  the  values  given 
to  vary  as  follows  : — 

Silver  =  100.  Copper  =  100. 

Jahresb.  d.  Chemie     .         .         .  f  49.10  at  0° 

I  $1.18  at  100° 

Margottet 33.74  51.5 

Mattheisen           .         .         .                  33.76  43.8 

Watts 56.1 

Benoit                                                        49.7  55.2 


THERMAL  CONDUCTIVITY. 

Deville :  It  is  generally  admitted  that  conductivity  for  heat 
and  electricity  correspond  exactly  in  the  different  metals.  A 
very  simple  experiment  made  by  Mr.  Faraday  in  his  laboratory 
seems  to  place  aluminium  very  high  among  metallic  conductors. 
He  found  that  it  conducted  heat  better  than  silver  or  copper. 

It  is  altogether  probable  that  there  was  some  mistake  made  in 
Faraday's  experiment,  since,  as  we  have  seen,  aluminium  is  inferior 
to  silver  and  copper  as  a  conductor  of  electricity,  and  recent 
investigations  also  place  it  inferior  to  them  in  thermal  conduc- 
tivity. The  writer  before  quoted  (Jahresb.  d.  Chemie),  gives 
these  values : — 

At  0°  At  100° 

Copper         ;.' 0.7198  0.7226 

Magnesium           .....     0.3760  0.3760 

Aluminium 0.3435  0.3619 

or  if  the  conductivity  of  copper  is  100,  that  of  aluminium  is 
47.72  at  0°  and  50.0  at  100°,  which  it  may  be  observed  agree 
very  closely  with  the  values  found  for  electric  conductivity  by 
the  same  investigator.  Calvert  and  Johnson  determined  the  ratio 
of  its  conducting  power  for  heat  with  that  of  silver  to  be  as  665 
is  to  1000,  which  is  considerably  higher  than  the  values  given  for 
electric  conductivity.  The  fact  that  these  values  agree  in  general 
better  when  referred  to  copper,  would  seem  to  show  that  the 
variable  quantity  is  probably  the  standard  silver  used  for  com- 
parison, although  we  should  have  expected  to  meet  with  more 
trouble  from  the  copper  in  this  respect. 


CHEMICAL   PROPERTIES   OF    ALUMINIUM.  71 


CHAPTER  IV. 

CHEMICAL    PROPERTIES    OF    ALUMINIUM. 

would  here  repeat  the  remark  made  with  regard  to  the 
physical  properties,  that  the  properties  to  be  recorded  are  those  of 
the  purest  metal  unless  specifically  stated  otherwise.  However, 
the  high  grade  of  commercial  metal  differs  very  little  in  most  of 
its  chemical  properties  from  the  absolutely  pure,  so  that  not  many 
reservations  are  necessary  in  applying  the  following  properties  to 
good,  commercial  metal : 

ACTION  OF  AIR. 

Deville :  Air,  wet  or  dry,  has  absolutely  no  action  on  alumin- 
ium. No  observation  which  has  come  to  my  knowledge  is  con- 
trary to  this  assertion,  which  may  easily  be  proved  by  any  one. 
I  have  known  of  beams  of  balances,  weights,  plaques,  polished 
leaf,  reflectors,  etc.,  of  the  metal  exposed  for  months  to  moist  air 
and  sulphur  vapors  and  showing  no  trace  of  alteration.  We  know 
that  aluminium  may  be  melted  in  the  air  with  impunity,  therefore 
air  and  also  oxygen  cannot  sensibly  affect  it:  It  resisted  oxidation 
in  the  air  at  the  highest  heat  I  could  produce  in  a  cupel  furnace, 
a  heat  much  higher  than  that  required  for  the  assay  of  gold.  This 
experiment  is  interesting,  especially  when  the  metallic  button  is 
covered  with  a  layer  of  oxide  which  tarnishes  it,  the  expansion  of 
the  metal  causing  small  branches  to  shoot  from  its  surface,  which 
are  very  brilliant  and  do  not  lose  their  lustre  in  spite  of  the  oxi- 
dizing atmosphere.  M.  Woliler  has  also  observed  this  property 
on  trying  to  melt  the  metal  with  a  blowpipe.  M.  Peligot  has 
profited  by  it  to  cupel  aluminium.  I  have  seen  buttons  of  im- 
pure metal  cupelled  with  lead  and  become  very  malleable. 

With  pure  aluminium  the  resistance  of  the  metal  to  direct  oxi- 
dation is  so  considerable  that  at  the  melting  point  of  platinum  it 


72  ALUMINIUM. 

is  hardly  Appreciably  touched,  and  does  not  lose  its  lustre.  It  is 
well  known  that  the  more  oxidizable  metals  take  this  property 
away  from  it.  But  silicon  itself,  which  is  much  less  oxidizable, 
when  alloyed  with  it  makes  it  burn  with  great  brilliancy,  because 
there  is  formed  a  silicate  of  aluminium. 

While  the  above  observations  are  in  the  main  true,  yet  it  is 
now  well  known  that  objects  made  of  commercial  aluminium  do 
after  a  long  exposure  become  coated  with  a  very  thin  film,  which 
gives  the  surface  a  "  dead"  appearance.  The  coating  is  very 
similar  in  appearance  to  that  forming  on  zinc  under  the  same 
circumstances.  The  oxidation,  however,  does  not  continue,  for 
the  film  seems  to  be  absolutely  continuous  and  to  protect  the 
metal  underneath  from  further  oxidation.  This  coating  can  best 
be  removed  by  very  dilute  acid  (see  Mourey's  receipt,  p.  57), 
after  which  the  surface  can  be  burnished  to  its  former  brilliancy- 

It  has  also  been  found  that  at  a  high  white-heat,  especially  at 
the  heat  of  an  electric  furnace,  aluminium  burns  with  a  strong  light 
to  alumina.  It  is  quite  probable  that  in  this  case  it  volatilizes 
first,  and  it  is  the  vapor  which  burns.  During  the  operation  of 
an  electric  furnace  a  white  smoke  formed  of  invisible  particles 
of  alumina  is  thus  formed  and  evolved  from  the  furnace.  Also, 
in  melting  aluminium,  even  the  purest,  it  will  be  found  that  the 
surface  seems  bound  and  the  aluminium  restrained  from  flowing 
freely  by  a  minute  "  skin'7  which  may  probably  be  a  mixture  of 
oxide  with  metal,  or  perhaps  of  oxides  of  foreign  metals,  but, 
nevertheless,  it  is  always  present  and  is  therefore  indicative  of 
oxidation  taking  place.  It  seems  to  protect  the  metal  beneath 
it  perfectly,  so  that,  ooice  formed,  it  gets  no  thicker  by  continued 
heating. 

Wohler  first  discovered  that  when  aluminium  was  in  the 
extremely  attenuated  form  of  leaf  it  would  burn  brightly  in  air, 
and  burn  in  oxygen  with  a  brilliant  bluish-light.  It  is  also  said 
that  thin  foil  will  burn  in  oxygen,  being  heated  by  wrapping  it 
around  a  splinter  of  wood,  and  fine  wire  also  burns  like  iron 
wire,  but  the  combustion  is  not  continuous  because  the  wire  fuses 
t  >  >  quickly.  The  alumina  resulting  is  quite  insoluble  in  acids, 
and  as  hard  as  corundum. 


CHEMICAL    PROPERTIES   OF   ALUMINIUM.  73 

ACTION  OF  WATER. 

Deville :  Water  has  no  action  on  aluminium,  either  at  ordi- 
nary temperatures  or  at  100°,  or  at  a  red  heat  bordering  on  the 
fusing  point  of  the  metal.  I  boiled  a  fine  wire  in  water  for  half 
an  hour  and  it  lost  not  a  particle  in  weight.  The  same  wire  was 
put  in  a  glass-tube  heated  to  redness  by  an  alcohol  lamp  and 
traversed  by  a  current  of  steam,  but  after  several  hours  it  had 
not  lost  its  polish,  and  had  the  same  weight.  To  obtain  any  sen- 
sible action  it  is  necessary  to  operate  at  the  highest  heat  of  a 
reverberatory  furnace — a  white  heat.  Even  then  the  oxidation  is 
so  feeble  that  it  develops  only  in  spots,  producing  almost  inap- 
preciable quantities  of  alumina.  This  slight  alteration  and  the 
analogies  of  the  metal  allow  us  to  admit  that  it  decomposes  water, 
but  very  feebly.  If,  however,  metal  produced  by  M.  Rose's 
method  is  used,  which  is  almost  unavoidably  contaminated  with 
slag  composed  of  chlorides  of  aluminium  and  sodium,  the  former, 
in  presence  of  water,  plays  the  part  of  an  acid  towards  alu- 
minium, disengaging  hydrogen  with  the  formation  of  a  subchlor- 
hydrate  of  alumina,  whose  composition  is  not  known,  and  which 
is  soluble  in  water.  When  the  metal  thus  tarnishes  in  water 
one  may  be  sure  to  find  chlorine  in  the  water  on  testing  it  with 
nitrate  of  silver. 

Aluminium  leaf,  however,  will  slowly  decompose  water  at 
100°.  Hydrogen  is  slowly  evolved,  the  leaf  loses  its  brilliancy, 
becomes  discolored,  and  after  some  hours  translucent.  It  is 
eventually  entirely  converted  into  gelatinous  hydrated  alumina. 

ACTION  OF  HYDROGEN  SULPHIDE  AND  SULPHUR. 

Deville :  Sulphuretted  hydrogen  exercises  no  action  on  alu- 
minium, as  may  be  proved  by  leaving  the  metal  in  an  aqueous 
solution  of  the  gas.  In  these  circumstances  almost  all  the  metals, 
and  especially  silver,  blacken  with  great  rapidity.  Sulph-hydrate 
of  ammonia  may  be  evaporated  on  an  aluminium  leaf,  leaving  on 
the  metal  only  a  deposit  of  sulphur,  which  the  least  heat  drives 
away. 

Aluminium  may  be  heated  in  a  glass  tube  to  a  red  heat  in 


74  ALUMINIUM. 

vapor  of  sulphur  without  altering  the  metal.  This  resistance  is 
such  that  in  melting  together  polysulphide  of  potassium  and 
some  aluminium  containing  copper  or  iron,  the  latter  are  attacked 
without  the  aluminium  being  sensibly  affected.  Unhappily,  this 
method  of  purification  may  not  be  employed  because  of  the  pro- 
tection which  aluminium  exercises  over  foreign  metals.  Under 
the  same  circumstances  gold  and  silver  dissolve  up  very  rapidly. 
However,  at  a  high  temperature  I  have  observed  that  it  com- 
bines directly  with  sulphur  to  give  aluminium  sulphide.  These 
properties  varying  so  much  with  the  temperature  form  one  of  the 
special  characteristics  of  the  metal  and  its  alloys. 

Margottet  states  that  hydrogen  sulphide  is  without  action  on 
aluminium,  as  also  are  the  sulphides  of  iron,  copper,  or  zinc. 
Aluminium  is  said  to  decompose  silver  sulphide,  Ag2S,  setting 
the  sulphur,  however,  at  liberty  and  alloying  with  the  silver.  In 
regard  to  its  indifference  to  the  first  mentioned  sulphides,  this 
would  give  inferential  evidence  that  the  reverse  operation,  i.  e., 
the  action  of  iron,  copper,  or  zinc  on  aluminium  sulphide,  would 
be  possible,  as  will  be  seen  later  to  be  apparently  established  by 
direct  experiment.  As  to  the  action  of  sulphuretted  hydrogen, 
the  author  has  a  different  experience  to  quote.  On  passing  a 
stream  of  that  gas  into  commercial  aluminium  melted  at  a  red 
heat,  little  explosive  puffs  were  heard  accompanied  by  a  yellow 
light,  while  the  dross  formed  on  the  surface,  when  cooled,  evolved 
sulphuretted  hydrogen  briskly  when  dropped  into  water,  and 
gave  every  indication  of  containing  aluminium  sulphide.  It 
could  not  have  been  silicon  sulphide,  for  the  metal  contained  as 
large  a  percentage  of  silicon  after  treatment  as  before.  Hydro- 
gen sulphide  is  also  absorbed  in  large  quantity  by  molten  alu- 
minium, and  mostly  evolved  just  as  the  metal  is  about  to  set. 
Some  of  the  gas  is  entangled  in  the  solidifying  metal,  forming 
and  filling  numerous  cavities  or  blow-holes. 

SULPHURIC  ACID. 

Deville:  Sulphuric  acid,  diluted  in  the  proportion  most  suit- 
able for  attacking  the  metals  which  decompose  water,  has  no 
action  on  aluminium ;  and  contact  with  a  foreign  metal  does  not 


CHEMICAL   PROPERTIES   OF   ALUMINIUM.  75 

help,  as  with  zinc,  the  solution  of  the  metal,  according  to  M.  de 
la  Rive.  This  singular  fact  tends  to  remove  aluminium  con- 
siderably from  those  metals.  To  establish  it  better,  I  left  for 
several  months  some  globules  weighing  only  a  few  milligrammes 
in  contact  with  the  weak  acid,  and  they  showed  no  visible  altera- 
tion ;  however,  the  acid  gave  a  faint  precipitate  when  neutralized 
with  aqua  ammonia. 

Margottet :  Sulphuric  acid,  dilute  or  concentrated,  exercises  in 
the  cold  only  a  very  slight  sensible  action  on  aluminium,  the  pure 
metal  is  attacked  more  slowly  than  when  it  contains  foreign 
metals.  The  presence  of  silicon  gives  rise  to  a  disengagement  of 
silicon  hydride  (SiH4),  which  communicates  to  the  hydrogen  set 
free  a  tainted  odor.  Concentrated  acid  dissolves  it  rapidly  with 
the  aid  of  heat,  disengaging  sulphurous  acid  gas  (SO2). 

NITRIC  ACID. 

Deville  :  Nitric  acid,  weak  or  concentrated,  does  not  act  on  alu- 
minium at  the  ordinary  temperature.  In  boiling  acid  solution 
takes  place,  but  with  such  slowness  that  I  had  to  give  up  this 
mode  of  dissolving  the  metal  in  my  analyses.  By  cooling  the 
solution  all  action  ceases.  On  account  of  this  property,  M.  Hulot 
obtained  good  results  on  substituting  aluminium  for  platinum  in 
the  Grove  battery. 

HYDROCHLORIC  ACID. 

Deville :  The  true  solvent  of  aluminium  is  hydrochloric  acid, 
weak  or  concentrated  ;  but,  when  the  metal  is  perfectly  pure,  the 
reaction  takes  place  so  slowly  that  M.  Favre,  of  Marseilles,  had 
to  give  up  this  way  of  attack  in  determining  the  heat  of  a  com- 
bination of  the  metal.  But,  impure  aluminium  is  dissolved  very 
rapidly.  At  a  very  low  temperature  gaseous  hydrochloric  acid 
attacks  the  metal  and  changes  it  into  chloride.  Under  these  cir- 
cumstances iron  does  not  seem  to  alter  ;  able,  no  doubt,  to  resist 
by  covering  itself  with  a  very  thin  protecting  layer  of  ferrous 
chloride.  This  experiment  would  lead  me  to  admit  that  it  is  the 
acid  and  not  the  water  \vhich  is  decomposed  by  aluminium ;  and, 


76  ALUMINIUM. 

in  fact,  the  metal  is  attacked  more  easily  as  the  acid  is  more  con- 
centrated. This  explains  the  difference  of  the  action  of  solutions 
of  hydrochloric  and  sulphuric  acids,  the  latter  being  almost  inac- 
tive. This  reasoning  applies  also  to  tin. 

When  the  metal  contains  silicon  it  disengages  hydrogen  of  a 
more  disagreeable  smell  than  that  given  out  by  iron  under  similar 
circumstances.  The  reason  of  this  is  the  production  of  that 
remarkable  body  recently  discovered  by  MM.  Wohler  and  Buff 
— silicuretted  hydrogen.  When  the  proportion  of  silicon  is 
small,  the  whole  is  evolved  as  gas ;  when  increased  a  little, 
some  remains  in  solution  with  the  aluminium,  and  then  it  re- 
quires great  care  to  separate  the  metal  exactly  even  when  the 
solution  is  evaporated  to  dry  ness.  If  3  to  5  per  cent,  of  silicon 
is  present,  it  remains  insoluble  mixed  with  a  little  silica,  as  has 
been  cleverly  proven  by  Wohler  and  Buff,  by  the  action  of  hydro- 
fluoric acid,  which  dissolves  the  silica  with  evolution  of  hydrogen 
without  attacking  the  silicon  itself.  On  dissolving  commercial 
aluminium  there  is  sometimes  obtained  a  black  crystalline  resi- 
due, which  separated  on  a  filter  and  dried  at  200°  to  300°  takes 
fire  in  places;  this  residue  is  silicon  mixed  with  some  silica.  The 
presence  of  silicon  augments  very  much  the  facility  with  which 
aluminium  is  attacked  by  hydrochloric  acid. 

If  hydrochloric  acid  is  present  in  a  mixture  of  acids,  it  begins 
the  destruction  of  the  metal.  Hydrobromic,  hydriodic,  hydro- 
fluoric acids  are  said  to  act  very  similarly  to  hydrochloric. 

ORGANIC  ACIDS,  VINEGAR,  ETC. 

Deville  :  Weak  acetic  acid  acts  on  aluminium  in  the  same  way 
as  sulphuric  acid,  i.  e.,  in  an  inappreciable  degree  or  with  extreme 
slowness.  I  used  for  the  experiment  acid  diluted  to  the  strength 
of  strongest  vinegar.  M.  Paul  Morin  left  a  plaque  of  the  metal 
a  long  time  in  wine  which  contained  tartaric  acid  in  excess  and 
acetic  acid,  and  found  the  action  on  it  quite  inappreciable.  The 
action  of  a  mixture  of  acetic  acid  and  common  salt  in  solution 
in  pure  water  on  pure  aluminium  is  very  different,  for  the  acetic 
acid  replaces  a  portion  of  the  chlorine  existing  in  the  sodium 


CHEMICAL   PROPERTIES   OF   ALUMINIUM.  77 

chloride,  rendering  it  free.  However,  this  action  is  very  slow, 
especially  if  the  aluminium  is  pure. 

The  practical  results  flowing  from  these  observations  deserve 
to  be  clearly  defined,  because  of  the  applications  which  may  be 
made  of  aluminium  to  culinary  vessels.  I  have  observed  that 
the  tin  so  often  used  and  which  each  day  is  put  in  contact  with 
common  salt  and  vinegar,  is  attacked  much  more  rapidly  than 
aluminium  under  the  same  circumstances.  Although  the  salts  of 
tin  are  very  poisonous,  and  their  action  on  the  economy  far  from 
being  negligible,  the  presence  of  tin  in  our  food  passes  unperceived 
because  of  its  minute  quantity.  Under  the  same  circumstances 
aluminium  dissolves  in  less  quantity  ;  the  acetate  of  aluminium 
formed  resolves  itself  on  boiling  into  insoluble  aluminia  or  an 
insoluble  sub-acetate,  having  no  more  taste  or  action  on  the  body 
than  clay  itself.  It  is  for  that  reason  and  because  it  is  known 
that  the  salts  of  the  metal  have  no  appreciable  action  on  the 
body,  that  aluminium  may  be  considered  as  an  absolutely  harm- 
less metal. 

It  may  be  appropriately  remarked  here  that  the  rapid  tar- 
nishing of  polished  aluminium  articles  is  more  frequently  due  to 
the  effect  of  handling  than  to  any  other  cause.  The  perspiration 
contains  about  2  per  cent,  of  sodium  chloride  and  about  an  equal 
quantity  of  organic  acids ;  its  action  on  aluminium  is  not  very 
great,  yet  almost  always  sufficient  to  spoil  a  high  polish  and  give 
a  visible  tarnish. 

AMMONIA. 

Aqua  ammonia  acts  slowly  on  aluminium,  producing  a  little 
alumina,  part  of  which  remains  dissolved.  Ammonia  gas  does  not 
appear  to  act  on  the  metal. 

CAUSTIC  ALKALIES. 

Deville :  Alkaline  solutions  act  with  great  energy  on  the 
metal,  transforming  it  into  aluminate  of  potash  or  soda,  setting 
free  hydrogen.  However,  it  is  not  attacked  by  caustic  potash  or 
soda  in  fusion ;  one  may,  in  fact,  drop  a  globule  of  the  pure 
metal  into  melted  caustic  soda  raised  almost  to  red  heat  in  a 


78  ALUMINIUM. 

silver  vessel,  without  observing  the  least  disengagement  of  hydro- 
gen. Silicon,  on  the  contrary,  dissolves  with  great  energy  under 
the  same  circumstances.  I  have  employed  melted  caustic  soda  to 
clean  siliceous  aluminium.  The  piece  is  dipped  into  the  bath 
kept  almost  at  red  heat.  At  the  moment  of  immersion  several 
bubbles  of  hydrogen  disengage  from  the  metallic  surface,  and 
when  they  have  disappeared  all  the  silicon  of  the  superficial 
layer  of  aluminium  has  been  dissolved.  It  only  remains  to  wash 
well  with  water  and  dip  it  into  nitric  acid,  when  the  aluminium 
takes  a  beautiful  mat.  Alkaline  organic  materials,  as  the  saliva, 
have  a  tendency  to  oxidize  it,  but  the  whole  effect  produced  is  in- 
significant. M.  Charriere  has  made  for  a  patient  on  whom  he 
practised  tracheotomy  a  small  tube  of  the  metal,  which  remained 
almost  unaltered  although  in  contact  with  purulent  matter. 
After  a  long  time  a  little  alumina  was  formed  on  it,  hardly 
enough  to  be  visible. 

Mallet :  The  pure  metal  presents  greater  resistance  to  the  pro- 
longed action  of  alkalies  than  the  impure. 

Aluminium  leaf  dissolves  with  extraordinary  quickness  in 
caustic  alkali,  leaving  the  iron,  which  is  always  present,  undis- 
solved.  The  chemical  reaction  occurring  indicates  that  aluminium 
acts  the  part  of  a  strong  acid,  forming  aluminates  of  the  alkaline 
metals  which  stay  in  solution. 

Lime  water  attacks  aluminium  in  a  similar  manner,  but  the 
resulting  calcium  aluminate  is  insoluble  in  water  and  is  therefore 
precipitated. 

SOLUTIONS  OF  METALLIC  SALTS. 

Deville  :  The  action  of  any  salt  whatever  on  aluminium  may 
be  easily  deduced  from  the  action  of  its  acids  on  that  metal. 
We  may,  therefore,  predict  that  in  acid  solutions  of  sulphates  and 
nitrates  aluminium  will  precipitate  no  metal,  not  even  silver,  as 
Wbhler  has  observed.  But  the  hydrochloric  solutions  of  the  same 
metals  will  be  precipitated,  as  MM.  Tissier  have  shown.  Like- 
wise, in  alkaline  solutions,  silver,  lead,  and  metals  high  in  the 
classification  of  the  elements  are  precipitated.  It  may  be  concluded 
from  this  that  to  deposit  aluminium  on  other  metals  by  means 
of  the  battery,  it  is  always  necessary  to  use  acid  solutions  in 


CHEMICAL    PROPERTIES    OF    ALUMINIUM.  79 

which  hydrochloric  acid,  free  or  combined,  should  be  absent. 
For  similar  reasons  the  alkaline  solutions  of  the  same  metals  can- 
not be  employed,  although  they  give  such  good  results  in  plating 
common  metals  with  gold  and  silver.  It  is  because  of  t  these 
curious  properties  that  gilding  and  silvering  aluminium  are  so  diffi- 
cult. 

These  conclusions  by  Deville  are  confirmed  only  when  using 
pure  aluminium  ;  the  impure  metal,  containing  iron,  silicon,  or 
perhaps  sodium,  may  produce  very  slight  precipitates  in  cases 
where  pure  aluminium  would  produce  none.  Some  observers 
have  noted  different  results  in  some  cases  even  when  using  alu- 
minium free  from  these  impurities.  We  will  therefore  take  up 
these  cases  and  consider  them  separately. 

Mercury. — *  Aluminium  decomposes  solutions  of  mercuric  chlor- 
ide, cyanide  or  nitrate,  mercury  separating  out  first  then  forming 
an  amalgam  with  the  aluminium  which  is  immediately  decom- 
posed by  the  water,  the  result  being  alumina  and  mercury.  From 
an  alcoholic  solution  of  mercurous  chloride  the  mercury  is  pre- 
cipitated more  quickly  at  a  gentle  heat.  A  solution  of  mercurous 
iodide  with  potassium  iodide  is  also  reduced  in  like  manner. 

Copper. — *From  solution  of  copper  sulphate  or  nitrate  alumin- 
ium separates  out  copper  only  after  two  days7  standing,  as  either 
dendrites  or  octahedra ;  from  the  nitrate  it  also  precipitates  a 
green,  insoluble  basic  salt.  Copper  is  precipitated  immediately 
from  a  solution  of  cupric  chloride  ;  but  slower  from  the  solution 
of  copper  acetate.  The  sulphate  or  nitrate  solutions  behave  simi- 
larly if  potassium  chloride  is  also  present,  and  the  precipitation  is 
complete  in  presence  of  excess  of  aluminium. 

Silver. — *From  a  nitrate  solution,  feebly  acid  or  neutral,  alu- 
minium precipitates  silver  in  dendrites,  the  separation  only  begin- 
ning after  six  hours'  standing.  From  an  ammoniacal  solution  of 
silver  chloride  or  chromate,  aluminium  precipitates  the  silver  im- 
mediately as  a  crystalline  powder.  fCossa  confirms  the  statement 
as  to  the  nitrate  solution. 

Lead. — *From  nitrate  or  acetate  solution  the  lead  is  slowly  pre- 

*  Dr.  Mierzinski. 

f  A.  Cossa,  Bull,  de  la  Soc.  Chim.  1870,  p.  199. 


80  ALUMINIUM. 

cipitated  in  crystals ;  an  alkaline  solution  of  lead  chromate  gives 
precipitates  of  lead  and  chromic  oxide. 

Zinc. — *An  alkaline  solution  of  zinc  salts  is  readily  decomposed 
and  zinc  precipitated. 

Margottet  states  that  all  metallic  chlorides  excepting  those  of 
potassium  or  sodium  are  reduced  from  solution.  This  statement 
can  hardly  include  chlorides  of  magnesium  or  lithium,  since  mag- 
nesium precipitates  alumina  from  solutions  of  aluminium  salts. 
Alkaline  or  ammoniacal  solutions  are  more  easily  decomposed  than 
acid  solutions ;  in  alkaline  solutions  the  cause  being  the  facility 
with  which  aluminates  of  the  alkaline  are  formed. 

Alkaline  chlorides. — A  solution  of  sodium  or  potassium  chlor- 
ide is  not  affected  by  pure  aluminium,  either  cold  or  warm. 
However,  aluminium  which  was  packed  in  a  case  with  saw-dust 
and  kept  wet  with  sea-water  for  two  weeks  was  deeply  corroded ; 
whether  the  result  would  have  been  the  same  without  the  pres- 
ence of  the  saw-dust,  I  cannot  say. 

Aluminium  salts. — It  is  a  curious  fact  that  a  solution  of  alu- 
minium chloride  will  attack  aluminium,  forming  sub-chlorhydrate, 
with  evolution  of  hydrogen.  A  solution  of  alum  does  not  attack 
aluminium,  but  if  sodium  chloride  is  added  it  is  dissolved  with 
evolution  of  hydrogen.  It  is  interesting  to  note  that  while  neither 
of  these  salts  alone  attacks  aluminium,  the  mixture  of  the  two  does. 

SODIUM  CHLORIDE. 

Fused  common  salt  is  used  as  a  flux  for  aluminium.  It  does 
not  possess  the  property,  like  fluorspar,  of  dissolving  alumina, 
but  it  is  apparently  without  any  corroding  effect  on  the  molten 
aluminium ;  neither  is  it  probable  that  it  is  capable  of  reacting 
alone  with  any  aluminous  material  to  form  aluminium  chloride, 
which  might  volatilize  and  thus  cause  loss  of  material. 

FLUORSPAR. 

This  compound  is  said  to  be  without  action  on  molten  alumin- 
ium. It  makes  a  good  flux  for  the  metal,  especially  in  connection 

*  A.  Cossa,  Bull,  de  la  Soc.  Chim.  1870,  p.  199. 


CHEMICAL   PROPERTIES   OF   ALUMINIUM.  81 

with  cryolite  or  common  salt,  and  possesses  the  property  of  dis- 
solving the  alumina  with  which  the  metal  may  be  contaminated 
and  which,  by  encrusting  small  globules,  hinders  their  reunion  to 
a  button. 

CRYOLITE. 

This  salt  is  largely  used  as  a  flux  for  aluminium  and  also  as  a 
source  of  the  metal.  It  is  commonly  supposed  to  have  the  prop- 
erty of  dissolving  alumina,  like  fluorspar,  but  to  be  without 
action  on  the  metal  itself.  Prof.  W.  Hampe,  however,  has  re- 
cently stated  that  at  a  temperature  about  the  melting  point  of  cop- 
per, finely-divided  aluminium  is  rapidly  dissolved,  a  sub-fluoride 
being  probably  formed ;  but  the  metal  "  en  masse"  is  not  sensibly 
attacked. 

SILICATES  AND  BORATES. 

Neither  of  these  classes  of  compounds  can  be  used  as  fluxes  or 
slags  in  working  aluminium,  since  they  both  rapidly  corrode  the 
metal.  Deville  had  little  difficulty  in  decomposing  these  salts  so 
completely  with  metallic  aluminium  that  he  isolated  silicon  and 
boron.  If  aluminium  is  melted  in  an  ordinary  glass  vessel  it 
attacks  it,  setting  free  silicon  from  silica,  forming  an  aluminate 
with  the  alkali  present  and  an  alloy  with  the  silicon  set  free.  Alu- 
minium melted  under  borax  is  rapidly  dissolved,  an  aluminium 
borate  being  formed.  It  is  thus  seen  that  the  common  metal- 
lurgic  slags  are  altogether  excluded  from  the  manufacture  of 
aluminium. 

NITRE. 

Deville :  Aluminium  may  be  melted  in  nitre  without  under- 
going the  least  alteration,  the  two  materials  rest  in  contact  with- 
out reacting  even  at  a  red  heat,  at  which  temperature  the  salt  is 
plainly  decomposed,  disengaging  oxygen  actively.  But  if  the 
heat  is  pushed  to  the  point  where  nitrogen,  itself  is  disengaged, 
there  the  nitre  becomes  potassa,  a  new  affinity  becomes  manifest, 
and  the  phenomena  change.  The  metal  then  combines  rapidly 
with  the  potassa  to  give  aluminate  of  potash.  The  accompanying 


82  ALUMINIUM. 

phenomenon  of  flagration  often  indicates  a  very  energetic  reac- 
tion. Aluminium  is  continually  melted  with  nitre  at  a  red  heat 
to  purify  it  by  the  oxygen  disengaged,  without  any  fear  of  loss. 
But  it  is  necessary  to  be  very  careful  in  doing  it  in  an  earthen 
crucible.  The  silica  of  the  crucible  is  dissolved  by  the  nitre,  the 
glass  thus  formed  is  decomposed  by  the  aluminium,  and  the  sili- 
cide  of  aluminium  formed  is  then  very  oxidizable,  especially  in 
the  presence  of  alkalies.  The  purification  by  nitre  ought  to  be 
made  in  an  iron  crucible  well  oxidized  by  nitre  inside. 

If  finely  divided  aluminium  is  mixed  with  nitre  and  brought 
to  a  red  heat,  the  metal  is  oxidized  with  the  production  of  a  fine 
blue  flame.  (Mierzinski.) 

ALKALINE  SULPHATES  AND  CARBONATES. 

Tissier :  Only  2.65  grammes  of  aluminium  introduced  into 
melted  red-hot  sodium  sulphate  (Na2SO4)  decomposed  that  salt 
with  such  intensity  that  the  crucible  was  broken  into  a  thousand 
pieces,  and  the  door  of  the  furnace  blown  to  a  distance.  Heated 
to  redness  with  alkaline  carbonate,  the  aluminium  was  slowly 
oxidized  at  the  expense  of  the  carbonic  acid,  carbon  was  set  free, 
and  an  aluminate  formed.  The  reaction  takes  place  without 
deflagration. 

METALLIC  OXIDES. 

Tissier  Brothers  made  a  series  of  experiments  on  the  action  of 
aluminium  on  metallic  oxides.  Aluminium  leaf  was  carefully 
mixed  with  the  oxide,  the  mixture  placed  in  a  small  porcelain 
capsule  and  heated  in  a  small  earthen  crucible,  which  served  as  a 
muffle.  The  results  were  as  follows  : — 

Manganese  dioxide. — No  reaction. 

Zinc  oxide. — No  reaction  even  at  white  heat. 

Ferric  oxide. — By  heating  to  white  heat  1  equivalent  of  ferric 
oxide  and  3  of  aluminium  the  reaction  took  place  with  detona- 
tion, and  by  heating  sufficiently  we  obtained  a  metallic  but- 
ton, well  melted,  containing  69.3  per  cent,  of  iron  and  30.7  per 
cent,  of  aluminium.  Its  composition  corresponds  very  nearly  to 
the  formula  AlFe.  It  would  thus  appear  that  the  decomposition 


CHEMICAL   PROPERTIES   OF   ALUMINIUM.  83 

of  ferric  oxide  will  not  pass  the  limit  where  the  quantity  of  iron 
reduced  is  sufficient  to  form  with  the  aluminium  the  alloy  AlFe. 

Lead  oxide. — We  mixed  2  equivalents  of  litharge  with  1  of  alu- 
minium, and  heated  the  mixture  slowly  up  to  white  heat,  when 
the  latter  reacted  on  the  litharge  with  such  intensity  as  to  produce 
a  strong  detonation.  We  made  an  experiment  with  50  grammes 
of  litharge  and  2.9  grammes  of  aluminium  leaf,  when  the  crucible 
was  broken  to  pieces  and  the  doors  of  the  furnace  blown  off. 

Copper  oxide. — Three  grammes  of  black  oxide  of  copper  mixed 
with  1.03  grammes  of  aluminium  detonated,  producing  a  strong 
explosion,  when  the  heat  reached  whiteness. 

Beketoff*  reduced  baryta  (BaO)  with  metallic  aluminium  in 
excess,  and  obtained  alloys  of  aluminium  and  barium  containing 
in  one  case  24  per  cent,  in  another  33  per  cent,  of  barium. 

MISCELLANEOUS  AGENTS. 

Phosphate  of  lime.  —  Tissier  Brothers  heated  to  whiteness  a 
mixture  of  calcium  phosphate  with  aluminium  leaf,  without  the 
metal  losing  its  metallic  appearance  or  any  reaction  being  noted. 

Hydrogen. — This  gas  appears  to  have  no  action  on  aluminium, 
except  to  be  dissolved  in  it  in  a  moderately  large  quantity. 

Chlorine. — Gaseous  chlorine  attacks  the  metal  rapidly.  Alu- 
minium foil  heated  in  an  atmosphere  of  chlorine  takes  fire  and 
burns  with  a  vivid  light. 

Bromine,  iodine,  fluorine  act  similarly  to  chlorine. 

Silver  chloride. — Fused  silver  chloride  is  decomposed  by  alu- 
minium, the  liberated  silver  as  well  as  the  excess  of  aluminium 
being  melted  by  the  heat  of  the  reaction. 

Mercurous  chloride.— If  vapors  of  mercurous  chloride  are  passed 
through  a  tube  in  which  some  hot  aluminium  is  placed,  mercury 
is  separated  out,  aluminium  chloride  deposits  in  the  cooler  part  of 
the  tube,  and  the  aluminium"  is  melted  by  the  heat  developed. 

*  Bull,  de  la  Soc.  Chimique,  1887,  p.  22. 


84  ALUMINIUM. 

GENERAL  OBSERVATIONS  ON  THE  PROPERTIES  OF  ALUMINIUM. 

Deville  :  "  Aluminium  at  a  low  temperature  conducts  itself  as 
a  metal  which  can  give  a  very  weak  base ;  in  consequence,  its  re- 
sistance to  acids,  hydrochloric  excepted,  is  very  great.  It  con- 
ducts itself  with  the  alkalies  as  a  metal  capable  of  giving  a  quite 
energetic  acid,  it  being  attacked  by  alkaline  oxides  dissolved  in 
water.  But  this  affinity  is  still  insufficient  to  determine  the 
decomposition  of  melted  caustic  potash.  For  a  stronger  reason 
it  does  not  decompose  metallic  oxides  at  a  red  heat.  This  is  why 
in  the  muffle  the  alloy  of  aluminium  and  copper  gives  black 
CuO,  and  this  also  accounts  for  the  alloy  of  aluminium  and  lead 
being  capable  of  being  cupelled.  But  by  a  strange  exception, 
and  which  does  not  appertain  solely,  I  believe,  to  aluminium,  as 
soon  as  the  heat  is  above  redness  the  affinities  are  quickly  in- 
verted and  the  metal  takes  all  the  properties  of  silicon,  decom- 
posing the  oxides  of  lead  and  copper  with  the  production  of  the 
aluminates. 

"  From  all  the  experiments  which  have  been  reported  and  from 
all  the  observations  which  have  been  made,  we  can  conclude  that 
aluminium  is  a  metal  which  has  complete  analogies  with  no  one 
of  the  simple  bodies  which  we  consider  metals.  In  1855,  I  pro- 
posed to  place  it  alongside  of  chromium  and  iron,  leaving  zinc 
out  of  the  group  with  which  aluminium  had  been  until  then 
classed.  Zinc  is  placed  very  well  beside  magnesium,  there  being 
intimate  analogies  between  these  two  volatile  metals.  There  may 
be  found  at  the  end  of  a  memoir  which  M.  Wohler  and  I  pub- 
lished in  the  '  Compt.  Rendue'  and  the  '  Ann.  de  Chem.  et  de 
Phys./  the  reasons  why  we  are  tempted  to  place  aluminium  near 
to  silicon  and  boron  in  the  carbon  series,  on  grounds  analogous 
to  those  on  which  antimony  and  arsenic  are  placed  in  the  nitro- 
gen series." 


ALUMINIUM   COMPOUNDS.  85 


CHAPTER  Y. 

PROPERTIES  AND  PREPARATION  OP  ALUMINIUM  COMPOUNDS. 

IN  this  chapter  we  propose  to  note  in  rather  condensed  form 
the  prominent  characteristics  of  the  various  aluminium  com- 
pounds, with  an  outline  of  the  methods  by  which  they  can  be 
produced,  reserving  for  another  chapter  however,  the  preparation 
of  those  salts  which  are  now  being  manufactured  on  a  commer- 
cial scale  for  purposes  of  further  treatment  for  aluminium.  I  do 
not  propose  this  as  a  substitute  for  the  various  chemical  treatises 
on  this  subject,  but  simply  to  add  to  the  completeness  of  this 
work  in  order  that  a  fair  understanding  of  the  other  parts  of  the 
book  may  not  be  missed  because  data  of  this  nature  are  not 
immediately  at  hand.  Parts  of  this  chapter  are  taken  from  M. 
Margottet's  treatise  on  aluminium,  in  Fremy's  Enclycopedie 
Chimique. 

GENERAL  CONSIDERATIONS. 

Structure  of  aluminium  compounds*  —  Aluminium  is  a  quad- 
rivalent element,  but  in  its  compounds  always  acts  as  a  double 
hexad  atom  (Al-  Al)vi,  one  bond  or  affinity  thus  serving  to  bind 
the  two  atoms  together.  The  double  atom  Al2  can  thus  unite 
with  six  rnonatomic  elements  or  atomic  groups,  or  their  equiva- 
lent. Thus  we  have  — 

A1203         Aluminium  oxide. 
A12(OH)6  "  oxyhydrate. 

"  chloride. 


The  salts  of  aluminium  usually  called  aluminious  salts,  are 
chemically  considered  as  derivatives  of  the  oxy  hydrate,  the  hydro- 
gen atoms  being  replaced  by  acid  radicals.  Thus  — 

*  R.  Biedermann.     Kerl  and  Stohmans,  Handbuch,  4th  ed. 


86        .  ALUMINIUM. 

A12.06.(N02)6      Aluminium  nitrate. 
A12.06.(C*H30)6  "  acetate. 

AK06.(S02)3  "          sulphate. 

A12.()6.(PO)2  «  phosphate. 

The  above  are  normal  or  neutral  salts,  all  the  hydrogen  atoms 
having  been  replaced.  Basic  salts  result  if  only  part  of  the  hy- 
drogen is  replaced. 

A12.(OH)*02.(C2H30)2  Basic  aluminium  acetate. 
A12.(OH*)02.(SO*)  "  "  sulphate. 

Aluminium  is  very  apt  to  form  these  basic  compounds  and 
others  of  even  greater  complexity. 

Aluminium  oxyhydrate  is  distinguished  from  most  of  the 
other  basic  oxides  in  that  its  hydrogen  atoms  are  not  alone 
replaced  by  acid  radicals,  but  by  metals  forming  aluminates. 
Thus— 

Al2.06.Na6    Sodium  aluminate. 
AR06.Ba3     Barium          " 

If  we  consider  aluminium  oxyhydrate  to  act  in  these  com- 
pounds as  an  acid,  these  are  its  neutral  salts.  Besides  alu- 
minates of  this  form  there  are  others,  natural  and  artificial, 
having  the  general  formula  APRO4,  R  being  diatomic.  These 
were  written  on  the  old  dualistic  theory  A12O3.RO,  but  they  are 
now  considered  as  derivatives  of  aluminium  anhydro-hydrate. 
Thus— 

A1202.(OH)2    Aluminium  anhydrohydrate, 
Al202.(02Mg)  Magnesium  aluminate. 

General  methods  of  formation  and  properties. — Hydrated  alu- 
mina, which  has  not  been  too  strongly  heated,  dissolves  in  strong 
acids  forming  salts  which  are  mostly  soluble  in  water.  In  the 
feebler  acids  and  in  all  organic  acids  it  is  completely  insoluble. 
The  salts  of  these  latter  acids  are  formed  best  by  decomposing 
solution  of  aluminium  sulphate  with  the  barium  or  lead  salt  of  the 
acid  in  question.  Alumina  forms  no  carbonate.  Most  alumin- 
ium salts  are  soluble  in  water  and  rather  difficult  to  crystallize  : 
the  few  insoluble  salts  are  white,  gelatinous,  and  similar  to  the 
hydrate  in  appearance.  In  the  neutral  salts  the  acid  is  loosely 
held,  for  their  solution  strongly  reddens  litmus  paper  and  their 


ALUMINIUM   COMPOUNDS.  .         87 

action  is  as  if  part  of  the  acid  were  free  in  the  salt.  For  in- 
stance,-a  solution  of  alum  attacks  iron  giving  off  hydrogen,  a 
soluble  basic  salt  of  aluminium  being  formed  as  well  as  sulphate 
of  iron.  The  neutral  salts  of  volatile  acids  give  off  acid  simply 
by  boiling  their  solutions,  basic  salts  being  formed.  An  aqueous 
solution  of  aluminium  chloride  loses  its  acid  almost  completely 
on  evaporation.  Gentle  ignition  is  sufficient  in  most  cases  to 
completely  decompose  aluminium  salts.  Hydrated  alumina  dis- 
solves easily  in  caustic  alkali  forming  soluble  aluminates  ;  with 
baryta  two  aluminates  are  known,  one  soluble  the  other  not ;  all 
other  known  aluminates  are  insoluble. 

Neutral  solutions  of  aluminium  salts  react  as  follows  with  the 
common  reagents  : — 

Hydrogen  sulphide  produces  no  precipitate. 

Ammonium  sulphide  precipitates  aluminium  hydrate  with  sepa- 
ration of  free  sulphur. 

Caustic  potash  or  soda  precipitates  aluminium  hydrate,  soluble 
in  excess. 

Aqua  ammonia  precipitates  aluminium  hydrate  insoluble  in 
excess,  especially  in  presence  of  ammoniacal  salts. 

Alkaline  carbonates  precipitate  aluminium  hydrate  insoluble  in 
excess. 

Sodium  phosphate  precipitates  white  gelatinous  aluminium 
phosphate,  easily  soluble  in  acids  or  alkalies. 

ALUMINIUM  OXIDE. 

Commonly  called  alumina.  Composition  APO3,  and  contains 
52.95  per  cent,  of  aluminium  when  perfectly  pure.  Colorless 
corundum  is  a  natural  pure  alumina,  in  which  state  it  is  infusible 
at  ordinary  furnace  heats,  insoluble  in  acids,  has  a  specific  gravity 
of  4,  and  is  almost  as  hard  as  the  diamond.  To  get  this  into 
solution  it  must  be  first  fused  with  potassium  hydrate  or  bisul- 
phate.  The  alumina  made  by  igniting  aluminium  hydrate  or 
sulphate  is  a  white  powder,  easily  soluble  in  acids  if  the  ignition 
has  been  gentle,  but  becoming  almost  insoluble  if  the  heat  has 
been  raised  to  whiteness.  The  specific  gravity  of  this  ignited 
alumina  also  varies  with  the  temperature  to  which  it  has  been 


88  ALUMINIUM. 

raised ;  if  simply  to  red  heat,  it  is  3.75 ;  if  to  bright-redness, 
3.8  ;  and  if  to  whiteness,  3.9.  In  the  last  case  it  acquires  almost 
the  hardness  of  corundum.  It  can  be  melted  to  a  clear,  limpid 
liquid  in  the  oxyhydrogen  blowpipe;  after  cooling  it  forms  a 
clear  glass,  often  crystallized.  Gaseous  chlorine  does  not  act  on 
it  even  at  redness,  but  if  carbon  is  present  at  the  same  time  alu- 
minium chloride  is  formed.  Similarly,  although  neither  carbon 
nor  sulphur,  alone  or  mixed  together,  acts  on  aluminium,  carbon 
bisulphide  converts  it  into  aluminium  sulphide. 

The  preparation  of  alumina  is  described  at  length  in  the  next 
chapter. 

ALUMINIUM  HYDRATES. 

There  are  three  natural  hydrates  of  aluminium,  which  may  be 
briefly  described  as  follows  : — 

Diaspore,  formula  A12O3.H2O  or  A12O2.(OH)2,  containing  85 
per  cent,  of  alumina,  occurs  in  crystalline  masses  as  hard  as 
quartz,  with  a  specific  gravity  of  3.4.  Bauxite,  of  the  general 
formula  A12O3.2H2O  or  APO.(OH)4,  with  the  aluminium  replaced 
by  variable  quantities  of  iron.  If  perfectly  pure,  it  would  con- 
tain 74  per  cent,  of  alumina.  Hydrochloric  acid  removes  from 
it  only  the  iron,  heated  with  moderately  dilute  sulphuric  acid  it 
gives  up  its  alumina,  a  concentrated  alkaline  solution  also  dis- 
solves the  alumina.  Calcined  with  sodium  carbonate  it  forms 
sodium  aluminate  without  melting.  Gibbsite,  formula  APO3.- 
3H2O  or  AP(OH)6,  containing  when  pure  65  per  cent,  of  alu- 
mina, is  a  mineral  generally  stalactitic,  white,  and  with  a  specific 
gravity  of  2.4.  It  loses  two-thirds  of  its  water  at  300°  and  the 
rest  at  redness. 

The  artificial  hydrates  are  of  two  kinds,  the  soluble  and  in- 
soluble modifications.  The  latter  is  the  common  hydrate,  such 
as  is  obtained  by  adding  ammonia  to  a  solution  containing  alu- 
minium. The  precipitate  is  pure  white,  very  voluminous,  and 
can  be  washed  free  from  the  salts  with  which  it  was  precipitated 
only  with  great  difficulty.  Its  composition  is  AP(OH)6,  corre- 
sponding to  the  mineral  gibbsite.  It  is  insoluble  in  water,  but 
easily  soluble  in  dilute  acids  or  alkali  solutions.  It  dissolves  in 


ALUMINIUM   COMPOUNDS.  89 

small  quantity  in  ammonia,  but  the  presence  of  ammonia  salts 
counteracts  this  action.  When  dissolved  in  caustic  potash  or  soda 
the  addition  of  ammoniacal  salts  reprecipitates  it.  It  loses  its 
water  on  heating,  in  the  same  manner  as  gibbsite.  Many  other 
properties  of  this  hydrate,  and  its  manufacture  on  a  large  scale, 
are  given  in  the  next  chapter.  The  soluble  modification  can  only 
be  made  by  complicated  processes,  too  long  to  be  described  here, 
and  is  principally  of  use  in  the  dyeing  industries ;  a  full  descrip- 
tion can  be  found  in  any  good  chemical  dictionary. 

ALUMINATES. 

Potassium  aluminate. — Formula  K2APO,  crystallizes  with  3 
molecules  of  water,  the  crystals  containing  40  per  cent,  alumina, 
37.5  per  cent,  potassa  and  21.5  per  cent,  of  water.  It  is  formed 
when  precipitated  alumina  is  dissolved  in  caustic  potash,  or  by 
melting  together  alumina  and  caustic  potash  in  a  silver  dish  and 
dissolving  in  water.  If  the  solution  is  evaporated  in  vacuo,  bril- 
liant hard  crystals  separate  out.  They  are  soluble  in  water  but 
insoluble  in  alcohol. 

Sodium  aluminate  has  not  been  obtained  crystallized.  Ob- 
tained in  solution  by  dissolving  alumina  in  caustic  soda  or  by 
fusing  alumina  with  caustic  soda  or  sodium  carbonate  and  dis- 
solving in  water.  If  single  equivalents  of  carbonate  of  soda  and 
alumina  are  used,  the  aluminate  seems  to  have  the  composition 
^a2APO4 ;  if  an  excess  of  soda  is  used,  the  solution  appears  to 
contain  AP(ONa)6,  or  APO.3Na2O.  If  a  solution  of  sodium 
aluminate  is  concentrated  to  20°  or  30°  B.,  alumina  separates 
out;  if  carbonic  acid  gas  is  passed  through  it,  aluminium  hydrate 
is  precipitated.  For  a  description  of  its  manufacture  on  a  large 
scale,  see  next  chapter. 

Barium  aluminate. — Formula  BaAPO.  Deville  prepared  it 
by  calcining  a  mixture  of  nitrate  or  carbonate  of  barium  with  an 
excess  of  alumina,  or  by  precipitating  sulphate  of  aluminium  in 
solution  by  baryta  water  in  excess.  The  aluminate  is  soluble  in 
about  10  times  its  weight  of  water  and  crystallizes  out  on  addition 
of  alcohol.  The  crystals  contain  4  molecules  of  water  Gaudin 
obtained  it  by  passing  steam  over  a  mixture  of  alumina  and 


90  ALUMINIUM. 

barium  chloride,  or  of  alumina,  barium  sulphate,  and  carbon,  at  a 
red  heat.  Tedesco  claimed  that  by  heating  to  redness  a  mixture  of 
alumina,  barium  sulphate,  and  carbon,  barium  aluminate  was  ex- 
tracted from  the  residue  by  washing  with  water.  He  utilized 
this  reaction  further  by  adding  solution  of  alkaline  sulphate,  bar- 
ium sulphate  being  precipitated  (which  was  used  over),  while 
alkaline  aluminate  remained  in  solution. 

Calcium  aluminate. — Lime  water  precipitates  completely  a 
solution  of  potassium  or  sodium  aluminate,  insoluble  gelatinous 
calcium  aluminate  being  formed,  of  the  formula  AP(O6Ca3)  or 
Al2O3.3CaO.  At  a  red  heat  it  melts  to  a  glass,  which,  treated 
after  cooling  with  boiling  solution  of  boric  acid,  affords  a  com- 
pound appearing  to  contain  2APO3.3CaO.  (Tissier.)  Lime  water 
is  also  completely  precipitated  by  hydrated  alumina,  the  com- 
pound formed  having  the  composition  CaAPO4  or  Al2O3.CaO. 
Also,  by  igniting  at  a  high  temperature  an  intimate  mixture  of 
equal  parts  of  aluminia  and  chalk,  Deville  obtained  a  fused  corn- 
pound  corresponding  to  the  formula  CaAPO4. 

Zinc  aluminate  occurs  in  nature  as  the  mineral  Gahnite, 
formula  ZnAPO4.  Berzelius  has  remarked  that  when  a  solution 
of  zinc  oxide  in  ammonia  and  a  saturated  solution  of  alumina  in 
caustic  potash  are  mixed,  a  compound  of  the  two  oxides  is  pre- 
cipitated, which  is  redissolved  by  an  excess  of  either  alkali. 

Copper  aluminate. — On  precipitating  a  dilute  solution  of  sodium 
aluminate  with  an  ammoniacal  solution  of  copper  sulphate,  the 
clear  solution  remaining  contained  neither  copper  nor  aluminium. 
Whether  the  precipitate  contained  these  combined  as  an  alu- 
minate I  was  not  able  to  determine. 

Magnesium  aluminate  occurs  in  nature  as  Spinell ;  iron  alu- 
minate as  Hercynite ;  beryllium  aluminate  as  Chrysoberyl.  I  can 
find  no  certain  information  of  their  artificial  production  except 
in  grains  at  a  very  high  heat. 

ALUMINIUM  CHLORIDE. 

Formula  APC1*  contains  20.2  per  cent,  of  aluminium.  The 
commercial  chloride  is  often  yellow  or  even  red  from  the  presence 
of  iron,  but  the  pure  salt  is  quite  white.  It  absorbs  water  very 


ALUMINIUM   COMPOUNDS.  91 

rapidly  from  the  air.  It  usually  sublimes  without  melting, 
especially  when  in  small  quantity,  but  if  a  large  mass  is  rapidly 
heated,  it  may  melt  and  even  boil,  but  its  melting  point  is  very 
close  to  its  boiling  point.  Its  vapor  condenses  at  180°  to  200°. 
When  sublimed  it  deposits  in  brilliant,  hexagonal  crystals.  A 
current  of  steam  rapidly  decomposes  it  into  alumina  and  hydro- 
chloric acid.  Oxygen  disengages  chlorine  from  it  at  redness,  but 
decomposes  it  incompletely.  Potassium  or  sodium  decomposes  it 
explosively,  the  action  commencing  below  redness.  Anhydrous 
sulphuric  acid  converts  it  into  aluminium  sulphate.  Aluminium 
chloride  combines  with  many  other  chlorides,  forming  the  double 
salts. 

On  dissolving  this  salt  in  water,  or  by  dissolving  alumina  in 
hydrochloric  acid,  a  solution  is  obtained  which  on  evaporation 
deposits  crystals  having  the  formula  A12C1M2H2O.  If  these 
crystals  are  heated,  they  decompose,  losing  both  water  and  acid 
and  leaving  alumina.  Thus,  it  is  not  possible  to  obtain  anhy- 
drous aluminium  chloride  by  evaporating  its  solution,  and  the 
anhydrous  salt  must  be  made  by  other  methods,  detailed  at  length 
in  the  next  chapter. 

ALUMINIUM-SODIUM  CHLORIDE. 

Formula  Al2Cl6.2NaCl  contains  14  per  cent,  of  aluminium. 
The  commercial  salt  is  often  yellow  or  brown  from  the  presence 
of  ferric  chloride,  but  the  pure  salt  is  perfectly  white.  Its  melt- 
ing point  has  been  generally  stated  to  be  180°,  but  Mr.  Baker, 
chemist  for  the  Aluminium  Company,  of  London,  states  that 
when  the  absolutely  pure  salt  is  warmed  it  melts  at  125°  to  130°. 
That  chemists  should  for  thirty  years  have  made  an  error  of  this 
magnitude  seems  almost  incredible,  and  it  would  be  satisfactory 
if  Mr.  Baker  would  advance  some  further  information  than  the 
bare  statement  above.  This  salt  volatilizes  at  a  red  heat  without 
decomposition.  It  is  less  deliquescent  in  the  air  than  aluminium 
chloride,  and  for  this  reason  is  much  easier  to  handle  on  a  large 
scale.  It  is  recently  stated  that  the  absolutely  pure  salt  deteri- 
orates less  than  the  impure  salt  in  the  air,  and  the  inference  is 
drawn  that  perhaps  the  greater  deliquescence  of  the  impure  salt 


92  ALUMINIUM. 

is  due  to  the  iron  chlorides  present.  Its  solution  in  water  behaves 
similarly  to  that  of  aluminium  chloride ;  it  cannot  be  evaporated 
to  dryness  without  decomposition,  the  residue  consisting  of  alu- 
mina and  sodium  chloride. 

The  manufacture  of  this  double  salt  on  a  large  scale  is  described 
in  the  next  chapter.  It  may  be  prepared  in  the  laboratory  by 
melting  a  mixture  of  the  two  component  salts  in  the  proper  pro- 
portions. A  similar  salt  with  potassium  chloride  may  be  prepared 
by  exactly  analogous  reactions. 

ALUMINIUM-PHOSPHORUS  CHLORIDE. 

Formula  A12C16.PC15,  contains  9  per  cent,  of  aluminium.  It 
is  a  white  salt,  easily  fusible,  volatilizes  only  about  400°  and  sub- 
limes slowly,  fumes  in  the  air  and  is  decomposed  by  water.  Pro- 
duced by  heating  the  two  chlorides  together  or  by  passing  vapor 
of  phosphorus  perchloride  over  alumina  heated  to  redness. 

ALUMINIUM-SULPHUR  CHLORIDE. 

Formula  A12C16.SC14,  contains  12.2  per  cent,  of  aluminium. 
It  forms  a  yellow  crystalline  mass,  fuses  at  100°,  may  be  distilled 
without  change,  and  is  decomposed  by  water.  May  be  obtained 
by  distilling  a  mixture  of  aluminium  chloride  and  ordinary  sul- 
phur chloride,  SCI2. 

ALUMINIUM-SELENIUM  CHLORIDE. 

Formula  Al2Cl6.SeCl4.  Obtained  by  heating  the  separate  chlor- 
ides together  in  a  sealed  tube,  when  on  careful  distillation  the 
less  volatile  double  chloride  remains.  It  is  a  yellow  mass,  melt- 
ing at  100°  and  decomposed  by  water. 

ALUMINIUM-AMMONIUM  CHLORIDE. 

Formula  A12C16.3NH3.  Solid  aluminium  chloride  absorbs 
ammonia  in  large  quantity,  the  heat  developed  liquefying  the 


ALUMINIUM   COMPOUNDS.  93 

resulting  compound.     It  may  be  sublimed  in  a  current  of  hydro- 
gen, but  loses  ammonia  thereby  and  becomes  APC1S.NH8. 

ALUMINIUM-CHLOR-SULPHYDRIDE. 

Formed  by  subliming  aluminium  chloride  in  a  current  of  hy- 
drogen sulphide.  A  current  of  hydrogen  removes  the  excess  of 
the  gas  used,  leaving  on  sublimation  fine  colorless  crystals.  In 
air  it  deliquesces  rapidly  and  loses  hydrogen  sulphide. 

ALUMINIUM-CHLOR-PHOSPHYDRIDE. 

Apparantly  of  the  formula  3A12C16.PH3.  If  phosphuretted 
hydrogen  is  passed  over  cold  aluminium  chloride  very  little  is 
absorbed,  but  at  its  subliming  point  it  absorbs  a  large  quantity, 
the  combination  subliming  and  depositing  in  crystals.  It  is  de- 
composed by  water  or  ammonium  hydrate,  disengaging  hydrogen 
phosphide. 

ALUMINIUM  BROMIDE. 

Formula  APBr8,  containing  10.1  per  cent,  of  aluminium.  It 
is  colorless,  crystalline,  melts  at  93°  to  a  clear  fluid  which  boils 
at  260°.  It  is  still  more  deliquescent  than  aluminium  chloride. 
At  a  red  heat  in  contact  with  dry  oxygen,  it  evolves  bromine 
and  forms  alumina  ;  it  is  also  decomposed  slowly  by  the  oxygen 
of  the  air.  It  dissolves  easily  in  carbon  bi-sulphide,  the  solution 
fuming  strongly  in  the  air.  It  reacts  violently  with  water,  the 
solution  on  evaporation  depositing  the  compound  Al2Br6.12H*O. 
The  same  result  is  attained  by  dissolving  alumina  in  hydrobromic 
acid  and  evaporating.  This  hydrated  chloride  is  decomposed  by 
heat  leaving  alumina.  The  specific  gravity  of  solid  aluminium 
bromide  is  2.5. 

This  compound  is  obtained  by  heating  aluminium  and  bromine 
together  to  redness,  or  by  passing  bromine  vapor  over  a  mixture 
of  alumina  and  carbon  at  bright  redness. 


94  ALUMINIUM. 

ALUMINIUM  IODIDE. 

Formula  API6,  containing  6.6  per  cent,  of  aluminium.  This 
compound  is  a  white  solid,  fusible  at  125°  and  boils  at  350°.  It 
dissolves  easily  in  carbon  bisulphide,  the  warm  saturated  solution 
depositing  it  in  crystals  on  cooling.  It  dissolves  also  in  alcohol 
and  ether.  Its  behavior  towards  water  is  exactly  analogous  to 
that  of  aluminium  bromide.  It  is  prepared  by  heating  iodine 
and  aluminium  together,  or  by  passing  iodine  vapor  over  an 
ignited  mixture  of  alumina  and  carbon. 

ALUMINIUM  FLUORIDE. 

Formula  A12F6,  containing  32.7  per  cent,  of  aluminium.  It 
is  sometimes  obtained  in  crystals  which  are  colorless  and  slightly 
phosphorescent.  They  are  insoluble  in  acids  even  in  boiling  sul- 
phuric, and  boiling  solution  of  potash  scarcely  attacks  them ;  they 
can  only  be  decomposed  by  fusion  with  sodium  carbonate  at  a 
bright  red  heat.  Melted  with  boric  acid,  aluminium  fluoride 
forms  crystals  of  aluminium  borate.  L.  Grabau  describes  the 
aluminium  fluoride  which  he  obtains  in  his  process,  as  being 
a  white  powder,  unalterable  in  air,  unaffected  by  keeping, 
insoluble  in  water,  infusible  at  redness,  but  volatilizing  at  a 
higher  temperature. 

Deville  first  produced  this  compound  by  acting  on  aluminium 
with  silicon  fluoride  at  a  red  heat.  He  afterwards  obtained  it 
by  moistening  pure  calcined  aluminium  with  hydrofluoric  acid, 
drying  and  introduced  into  a  tube  made  of  gas  carbon,  protected 
by  a  refractory  envelope.  The  tube  was  heated  to  bright  red- 
ness, a  current  of  hydrogen  passing  through  meanwhile  to  facili- 
tate the  volatilization  of  the  fluoride.  Brunner  demonstrated 
that  aluminium  fluoride  is  formed  and  volatilized  when  hydro- 
fluoric acid  gas  is  passed  over  red  hot  alumina.  Finally,  if  a 
mixture  of  fluorspar  and  alumina  is  placed  in  carbon  boats,  put 
into  a  carbon  tube,  suitably  protected,  heated  to  whiteness  and 
gaseous  hydrofluoric  acid  passed  over  it,  aluminium  fluoride  will 
volatilize  and  condense  in  the  cooler  part  of  the  tube  in  fine 
cubical  crystals,  while  calcium  chloride  remains  in  the  boats. 


ALUMINIUM  COMPOUNDS.  95 

ALUMINIUM  FLUORHYDRATE. 

When  calcined  alumina  or  kaolin  is  treated  with  hydrofluoric 
acid,  alumina  being  in  excess,  soluble  fluorhydrate  of  aluminium 
is  formed,  whiclj  deposits  on  evaporating  the  solution.  It  has 
the  formula  A12F6.7H2O,  and  easily  loses  its  water  when  heated. 

ALUMINIUM-HYDROGEN  FLUORIDE. 

If  to  a  strongly  acid  solution  of  alumina  in  hydrofluoric  acid 
alcohol  is  added,  an  oily  material  separates  out  and  crystallizes, 
having  the  formula  3A12F3.4HF.10H2O.  If  the  acid  solution  is 
simply  evaporated,  acid  fumes  escape  and  a  crystalline  mass  re- 
mains which,  washed  with  boiling  water  and  dried,  has  the  for- 
mula 2A12F3.HF.10H2O.  On  heating  these  compounds  to  400° 
or  500°  in  a  current  of  hydrogen,  pure  amorphous  aluminium 
fluoride  remains.  The  acid  solution  of  alumina  first  used  seems 
to  contain  an  acid  of  the  composition  A12F6.6HF,  which  is  capa- 
ble of  forming  salts  with  other  bases.  Thus,  if  this  solution  is 
neutralized  with  a  solution  of  soda,  a  precipitate  of  artificial  cryo- 
lite, Al2F6.6NaF,  falls.  The  similar  potash  compound  is  formed 
in  the  same  way. 

ALUMINIUM-SODIUM   FLUORIDE. 

Formula  Al2F6.6NaF,  containing  12.85  per  cent,  of  alumin- 
ium, occurs  native  as  cryolite,  a  white  mineral  with  a  waxy  ap- 
pearance, as  hard  as  calcite,  specific  gravity  2.9,  melting  below 
redness  and  on  cooling  looking  like  opaque,  milky  glass.  If  kept 
melted  in  moist  air,  or  in  a  current  of  steam,  it  loses  hydrofluoric 
acid  and  sodium  fluoride  and  leaves  a  residue  of  pure  alumina. 
When  melted  it  is  decomposable  by  an  electric  current  or  by 
sodium  or  magnesium.  It  is  insoluble  in  water,  unattacked  by 
hydrochloric  but  decomposed  by  hot  sulphuric  acid.  The  native 
mineral  is  contaminated  with  ferrous  carbonate,  silica,  phosphoric, 
and  vanadic  acids.  An  extended  description  of  its  utilization, 
manufacture,  etc.  will  be  found  in  the  next  chapter. 


96  ALUMINIUM. 

ALUMINIUM  SULPHIDE. 

Formula  APS3,  containing  36  per  cent,  of  aluminium.  The 
pure  salt  is  light  yellow  in  color  and  melts  at  a  high  temperature. 
In  damp  air  it  swells  up  and  disengages  hydrogen  sulphide,  form- 
ing a  grayish  white  powder ;  it  decomposes  water  very  actively, 
forming  hydrogen  sulphide  and  ordinary  gelatinous  aluminium 
hydrate.  Steam  decomposes  it  easily,  at  red  heat  forming  amorph- 
ous alumina,  which  is  translucent  and  very  hard.  Gaseous  hydro- 
chloric acid  transforms  it  into  aluminium  chloride.  Elements 
having  a  strong  affinity  for  sulphur  reduce  it,  setting  free 
aluminium,  but  it  is  doubtful  if  hydrogen  or  carburetted  hydro- 
gen has  this  effect. 

It  may  be  formed  by  throwing  sulphur  into  red-hot  alumin- 
ium, or  by  passing  sulphur  vapor  over  red-hot  aluminium. 
Traces  only  of  aluminium  sulphide  are  formed  by  passing  hydro- 
gen sulphide  over  ignited  alumina,  but  carbon-bisulphide  vapor 
readily  produces  this  reaction.  For  details  of  its  formation  see 
next  chapter. 

ALUMINIUM  SELENIDE. 

When  aluminium  is  heated  in  selenium  vapor,  the  two  elements 
combine  with  incandescence,  producing  a  black  powder.  In  the 
air  this  powder  evolves  the  odor  of  hydrogen  selenide  ;  in  con- 
tact with  water  it  disengages  that  gas  abundantly  and  furnishes 
a  red  deposit  of  selenium  along  with  aluminium  hydrate.  When 
a  solution  of  an  aluminium  salt  is  treated  with  an  alkaline  poly- 
selenide,  a  flesh-colored  precipitate  falls,  the  composition  of  which 
is  not  known,  which  is  decomposed  at  redness  leaving  aluminium. 

ALUMINIUM  BORIDES. 

A1B2,  containing  55.1  per  cent,  of  aluminium,  was  first  ob- 
tained by  Deville  and  Wohler  by  heating  boron  in  contact  with 
aluminium,  or  on  reducing  boric  acid  with  the  latter  metal,  the 
action  not  being  long  continued.  Also,  if  a  current  of  boron  tri- 
chloride with  carbonic  oxide  is  passed  over  aluminium  in  boats  in 


ALUMINIUM  COMPOUNDS.  97 

a  tube  heated  to  redness,  aluminium  chloride  volatilizes  and  there 
remains  in  the  boats  a  crystalline  mass,  cleavable,  and  covered 
with  large  hexagonal  plates  of  a  high  metallic  lustre.  To  re- 
move the  aluminium  present  in  excess  the  mass  is  treated  with 
hydrochloric  acid  and  then  by  caustic  soda.  The  final  residue  is 
composed  of  hexagonal  tablets,  very  thin  but  perfectly  opaque,  of 
about  the  color  of  copper.  These  crystals  do  not  burn  in  the  air, 
even  if  heated  to  redness,  but  their  color  changes  to  dark-gray. 
They  burn  in  a  current  of  chlorine,  giving  chlorides  of  the  two 
elements  contained  in  them.  They  dissolve  slowly  in  concen- 
trated hydrochloric  acid  or  in  solution  of  caustic  soda;  nitric 
acid,  moderately  concentrated,  attacks  them  quickly. 

A1BS,  containing  45  per  cent,  of  aluminium,  has  been  obtained 
by  Hampe  by  heating  aluminium  with  boric  acid  for  three  hours 
at  a  high  temperature,  carbon  being  carefully  kept  away.  On 
cooling  very  slowly,  the  upper  part  of  the  fusion  is  composed  01 
aluminium  borate,  the  centre  is  of  very  hard,  alumina  containing 
a  few  black  crystals  of  aluminium  boride,  while  at  the  bottom  is 
a  button  of  aluminium  also  containing  these  crystals.  To  free 
these  crystals,  the  aluminium  is  dissolved  by  hydrochloric  acid. 
These  crystals  are  the  compound  sought  for,  and  contain  no  other 
impurity  than  a  little  alumina,  which  can  be  removed  by  boiling 
sulphuric  acid.  These  purified  crystals  are  black,  but  are  thin 
enough  to  show  a  dark-red  by  transmitted  light.  Their  specific 
gravity  is  2.5,  they  are  harder  than  corundum,  but  are  scratched  by 
the  diamond.  Oxygen  has  no  action  on  them  at  a  high  tempera- 
ture, solution  of  caustic  potash  or  hydrochloric  acid  does  not  attack 
them,  boiling  sulphuric  acid  has  scarcely  any  action,  but  they 
dissolve  completely  in  warm,  concentrated  nitric  acid. 

If  the  operation  by  which  this  product  is  made  is  conducted  in 
the  presence  of  carbon,  the  compound  formed  contains  less  alu- 
minium and  also  some  carbon.  Its  composition  corresponds  to 
the  formula  A13C2B48,  containing  about  12  per  cent,  of  aluminium 
and  3.75  per  cent,  of  carbon.  The  crystals  of  this  compound  are 
yellow  and  as  brilliant  as  the  diamond.  Their  specific  gravity  is 
2.6,  hardness  between  that  of  corundum  and  the  diamond.  They 
are  not  attacked  by  oxygen,  even  at  a  high  temperature ;  hot 
hydrochloric  or  sulphuric  acid  attacks  them  only  superficially, 
7 


98  ALUMINIUM. 

concentrated  nitric  acid  dissolves  them  slowly  but  completely. 
They  resist  boiling  solution  of  caustic  potash  or  fused  nitre,  but 
take  fire  in  fused  caustic  potash  or  chromate  of  lead. 

ALUMINIUM  NITRIDE. 

Formula  AIN,  containing  66  per  cent,  of  aluminium,  is  formed 
when  aluminium  is  heated  in  a  carbon  crucible  to  a  high  tempera- 
ture. Mallet*  obtained  it  in  quantity  by  heating  aluminium  with 
dry  sodium  carbonate  at  a  high  heat,  for  several  hours,  in  a  car- 
bon crucible.  The  aluminium  is  partially  transformed  into  alu- 
mina, some  sodium  vaporizes  and  some  carbon  is  deposited.  After 
cooling,  there  are  found  on  the  surface  of  the  button  little  yellow 
crystals  and  amorphous  drops,  to  recover  which  the  whole  is  treated 
with  very  dilute  hydrochloric  acid.  This  product  has  the  com- 
position AIN.  Calcined  in  the  air  it  slowly  loses  nitrogen  and 
forms  alumina.  It  decomposes  in  moist  air,  loses  its  trans- 
parency, becomes  a  lighter  yellow7,  and  finally  only  alumina 
remains,  the  nitrogen  having  formed  ammonia.  Melted  with 
caustic  potash  it  disengages  ammonia  and  forms  potassium  alu- 
minate. 

ALUMINIUM  SULPHATE. 

Anhydrous. — The  salt  obtained  by  drying  hydrated  aluminium 
sulphate  at  a  gentle  heat  has  the  formula  A12(SO4)3,  containing 
15.8  per  cent,  of  aluminium,  and  of  a  specific  gravity  of  2.67. 
By  heating  this  salt  several  minutes  over  a  Bunsen  burner  it  loses 
almost  all  its  acid,  leaving  alumina.  Hydrogen  likewise  decom- 
poses it  at  redness,  forming  water  and  sulphur  dioxide  and  leav- 
ing alumina  with  hardly  a  trace  of  acid.  Melted  with  sulphur, 
Violi  states  that  it  is  transformed  into  aluminium  sulphide, 
evolving  sulphurous  acid  gas.f  Hot  hydrochloric  acid  in  excess 
partly  converts  it  into  aluminium  chloride. 

Hydrated. — This  is  the  ordinary  aluminium  sulphate;  its  form- 
ula is  A12(SO4)3.18H2O,  and  it  contains  8.4  per  cent,  of  alu- 

*  Ann.  der  Chemie  u.  Pharmacie,  186,  p.  155. 
f  Berichte  des  Deutschen  Gesellschaft,  X,  293. 


ALUMINIUM   COMPOUNDS.  99 

minium  and  47  per  cent,  of  water.  It  has  a  white,  crystalline 
appearance  and  tastes  like  alum.  It  dissolves  freely  in  water, 
from  which  it  crystallizes  out  at  ordinary  temperatures  with  the 
above  formula ;  crystallized  out  at  a  low  temperature  it  retains 
27H2O,  or  one-half  as  much  again.  Water  dissolves  one-half 
its  weight  of  this  salt,  the  solution  reacting  strongly  acid  ;  it  is 
almost  insoluble  in  alcohol.  At  a  gentle  heat  it  melts  in  its 
water  of  crystallization,  then  puifs  up  and  leaves  a  porous  mass  of 
anhydrous  sulphate  which  is  soluble  with  difficulty  in  water. 
If  heated  to  redness  it  leaves  only  alumina,  the  salt  with  18H2O 
has  a  specific  gravity  of  1.76  ;  it  is  the  salt  found  in  fibrous 
masses  in  solfataras,  its  mineralogical  name  being  Halotrichite. 
A  hydrated  sulphate  with  10H2O  is  formed  and  precipitated  when 
alcohol  is  added  to  an  aqueous  solution  of  aluminium  sulphate. 
On  heating  it  acts  similarly  to  the  other  hydrated  sulphates. 

.Basic. — On  precipitating  a  solution  of  aluminium  sulphate 
with  alkaline  hydrate  or  carbonate  a  series  of  basic  salts  are 
formed.  On  precipitating  with  ammonia,  the  compound  formed 
has  the  formula  A12O3.SO3.9H2O,  corresponding  to  the  mineral 
Aluminite.  If  the  ammonia  is  in  insufficient  quantity  to  entirely 
precipitate  the  solution,  a  precipitate  is  very  slowly  formed  hav- 
ing the  formula  3A12O3.2SO8.20H2O.  On  precipitating  a  cold 
solution  of  alum  by  alkaline  carbonate  not  in  excess,  a  precipitate 
is  very  slowly  formed  having  the  formula  2A12O3.SO3.12H2O.  If 
a  very  dilute  solution  of  acetate  of  alumina  is  precipitated  by 
adding  potassium  sulphate,  a  compound  deposits  very  slowly 
having  the  formula  2A12O3.SO3.10H2O.  Native  minerals  are  met 
with  of  analogous  composition  to  these  precipitates  :  Felsobanyte, 
2  A12O3.SO3.10H2O  ;  Paraluminite,  2A12O3.SO3.15H2O.  By  heat- 
ing a  concentrated  solution  of  aluminium  sulphate  with  aluminium 
hydrate,  and  filtering  cold,  the  solution  deposits  on  further  cooling 
a  gummy  mass  having  the  formula  A12O3.2SO8.#H2O.  On  wash- 
ing with  water  it  deposits  a  basic  salt  having  the  formula  A12O3.- 
SO3.  By  letting  stand  a  very  dilute  solution  of  sulphuric  acid 
completely  saturated  with  aluminium  hydrate,  Rammelsberg  ob- 
tained transparent  crystals  having  the  formula  3APO8.4SO3.- 
30H2O.  On  boiling  a  solution  of  aluminium  sulphate  with  zinc, 
Debray  obtained  a  granular  precipitate  having  the  formula 


100  ALUMINIUM. 

5A12O3.3SO3.20H2O.  By  leaving  zinc  a  long  time  in  a  cold  solu- 
tion of  aluminium  sulphate,  a  gelatinous  precipitate  was  obtained 
having  the  formula  4A12O3.3SO3.36H2O ;  the  same  compound 
was  formed  if  the  zinc  was  replaced  by  calcium  carbonate. 

The  manufacture  of  aluminium  sulphate  from  clay,  aluminous 
earths,  cryolite,  beauxite,  etc.  is  carried  on  industrially  on  a  very 
large  scale ;  descriptions  of  the  processes  used  may  be  found  in 
any  work  on  industrial  chemistry — they  are  too  foreign  to 
metallurgical  purposes  to  be  treated  of  here. 

ALUMS. 

Under  this  name  are  included  a  number  of  double  salts  con- 
taining water,  crystallizing  in  octahedra  and  having  the  general 
formula  R2SO4.R2(SO4)3.24H2O,  in  which  the  first  R  may  be  potass- 
ium, sodium,  rubidium,  caesum,  ammonium,  thallium  or  even  or- 
ganic radicals ;  the  second  R,  maybe  aluminium,  iron,  manganese  or 
chromium ;  the  acid  may  even  be  selenic,  chromic  or  manganic,  in- 
stead of  sulphuric.  We  will  briefly  describe  the  most  important 
alums  consisting  of  double  sulphates  of  aluminium  and  another 
metal,  remarking,  as  with  aluminium  sulphate,  that  their  prepara- 
tion may  be  found  at  length  in  any  chemical  treatise. 

POTASH  ALUM. 

Formula  K2SO4.A12(SO4)3.24H2O,  containing  10.7  per  cent,  of 
alumina  or  5.7  per  cent  of  aluminium.  Dissolves  in  25  parts  of 
water  at  0°  and  in  two-sevenths  part  at  100°.  The  solution  re- 
acts acid.  It  forms  colorless,  transparent  octahedrons,  insoluble 
in  alcohol.  On  exposure  to  air  they  become  opaque,  being  covered 
with  a  white  coating,  which  is  said  not  to  be  efflorescence — a  loss 
of  water — but  to  be  caused  by  absorption  of  ammonia  from  the 
air.  The  crystals  melt  in  their  water  of  crystallization,  but  lose 
it  all  above  100°.  Heated  to  redness  it  swells  up  strongly,  be- 
comes porous  and  friable,  giving  the  product  called  calcined  alum  ; 
at  whiteness  it  loses  a  large  part  of  its  sulphuric  acid,  leaving  a 
residue  of  potassium  sulphate  and  alumina.  If  it  is  mixed  with 
one-third  its  weight  of  carbon  and  calcined,  the  residue  inflames 


ALUMINIUM   COMPOUNDS.  101 

spontaneously  in  the  air.  If  a  mixture  of  alumina  and  bi-sul- 
phate  of  potassium  is  fused  and  afterwards  washed  with  warm 
water,  a  residue  is  obtained  of  anhydrous  alum,  or  K2SO4.- 
A12(SO4)3.  The  mineral  Alunite  is  a  basic  potash  alum,  K2SO4.- 
3(A12O3.SO3).6H2O. 

AMMONIA  ALUM. 

Formula(NH4)2SO4.Al2(SO4)3.24H2O,  containing  11.3  per  cent, 
of  alumina  or  6.0  per  cent,  of  aluminium.  Dissolves  in  20  parts 
of  water  at  0°  and  in  one-fourth  part  at  100°.  When  heated, 
the  crystals  swell  up  strongly,  forming  a  porous  mass,  losing  at 
the  same  time  water  and  sulphurous  acid  ;  if  the  temperature  is 
high  enough  there  remains  a  residue  of  pure  alumina.  The  tem- 
perature necessary  for  complete  decomposition  is  higher  than  that 
required  for  volatilising  ammonium  sulphate  alone. 

SODA  ALUM. 

Formula  Na2SO4.Al2(SO4)8.24H2O,  containing  11.1  per  cent,  of 
alumina  or  5.9  per  cent,  of  aluminium.  Dissolves  in  an  equal 
weight  of  water  at  ordinary  temperatures.  The  crystals  effloresce 
and  fall  to  powder  in  the  air.  It  is  insoluble  in  absolute  alcohol. 
On  account  of  its  great  solubility  in  water  it  cannot  be  separated 
from  ferrous  sulphate  by  crystallization,  and  therefore  it  is  either 
contaminated  with  much  iron  or  else,  to  be  obtained  pure,  special 
expensive  methods  must  be  adopted.  These  difficulties  cause  the 
manufacture  of  soda  alum  to  be  insignificant  in  amount  when 
compared  with  potash  alum. 

ALUMINIUM-METALLIC  SULPHATES. 

Sulphate  of  aluminium  forms  double  sulphates  with  iron,  man- 
ganese, magnesium  and  zinc,  but  these  compounds  are  not  analo- 
gous to  the  alums.  They  are  extremely  soluble  in  water,  do  not 
crystallize  in  octahedrons  or  any  isometric  forms,  and  their  com- 
position is  different  from  the  alums  in  the  amount  of  water  of 
crystallization.  It  has  been  determined  that  the  double  sulphates 


102  ALUMINIUM. 

with  manganese  and  zinc  contain  25  equivalents  of  water,  which 
would  permit  their  being  considered  as  combinations  of  sulphate 
of  aluminium,  A12(SO4)3.18H2O,  with  a  sulphate  of  the  magne- 
sian  series  containing  seven  equivalents  of  water,  as  ZnSO4.7H2O. 

ALUMINIUM  SELENITES. 

By  adding  a  solution  of  selenite  of  soda  to  one  of  sulphate  of 
aluminium  maintained  in  excess,  an  amorphous,  voluminous  pre- 
cipitate forms  having  the  composition  4APO3.9SeO2.3H2O.  This 
substance  decomposes  on  being  heated,  leaving  alumina.  If  vary- 
ing quantities  of  selenious  acid  are  added  to  this  first  salt,  other 
salts  of  the  formulas  Al2SO3.3SeO2.7H2O,2Al2O3.9SeO2.12H2O, 
Al2O3.6SeO2.5H2O  are  formed.  These  are  mostly  insoluble  in 
water  and  decompose  on  being  heated,  like  the  first. 

ALUMINIUM  NITRATE. 

Formula  A12(NO3)6.18H2O  is  obtained  on  dissolving  aluminium 
hydrate  in  nitric  acid.  If  the  solution  is  evaporated  keeping  it 
strongly  acid,  it  deposits  on  cooling  voluminous  crystals  having 
the  formula  A12(NO3)6.15H2O.  This  salt  is  deliquescent,  melts  at 
73°  and  gives  a  colorless  liquid  which,  on  cooling,  becomes  crystal- 
line. It  is  soluble  in  water,  nitric  acid,  and  alcohol ;  on  evapo- 
rating these  solutions  it  is  obtained  as  a  sticky  mass.  It  is  easily 
decomposed  by  heat;  if  kept  at  100°  for  a  long  time  it  loses  half 
its  weight,  leaving  as  residue  a  soluble  salt  of  the  formula  2A12O3.- 
3N2O5.3H2O.  Carried  to  140°,  this  residue  loses  all  its  nitric 
acid,  leaving  alumina.  On  this  property  is  based  a  separation  of 
alumina  from  lime  or  magnesia,  si  nee  the  nitrates  of  these  latter 
bases  resist  the  action  of  heat  much  better  than  aluminium  nitrate. 

ALUMINIUM  PHOSPHATES. 

The  normal  phosphate,  A12(PO4)2,  is  obtained  as  a  white,  gelat- 
inous precipitate  when  a  neutral  aluminium  solution  is  treated 
with  sodium  phosphate.  It  is  soluble  in  alkalies  or  mineral 
acids  but  not  in  acetic  acid.  If  a  solution  of  this  salt  in  acids  is 


ALUMINIUM   COMPOUNDS.  103 

neutralized  with  ammonia,  a  basic  phosphate  is  precipitated  hav- 
ing the  composition  3 A12(OH)3PO4  4- A12(OH)6.  The  mineral 
Wavellite  has  this  composition,  with  nine  molecules  of  water.  The 
mineral  Kalait  contains  A12(PO4)2  +  A12(OH)6  +  2H2O,  and  when 
it  is  colored  azure  blue  by  a  little  copper  it  forms  the  Turquois. 

ALUMINIUM  CARBONATE.  ' 

If  to  a  cold  solution  of  alum  a  cold  solution  of  sodium  carbon- 
ate is  added  drop  by  drop,  stirring  constantly  until  the  solution 
reacts  feebly  alkaline,  a  precipitate  is  obtained  which,  after  being 
washed  with  cold  water  containing  carbonic  acid  gas,  contains 
when  damp  single  equivalents  of  alumina  and  carbonic  acid, 
A12O3.CO2.  If  the  precautions  indicated  are  not  used,  the  pre- 
cipitate contains  a  very  small  proportion  of  carbonic  acid. 

ALUMINIUM  BORATE. 

Formula  3A12O3.BO3.  Prepared  by  Ebelman  by  heating 
together  alumina,  oxide  of  cadmium,  and  boric  acid.  After 
three  days'  heating  the  platinum  capsule  containing  the  mixture 
was  found  covered  with  transparent  crystals  of  the  above  com- 
position, hard  enough  to  scratch  quartz  and  having  a  specific 
gravity  of  3.  Troost  obtained  the  same  substance  by  heating 
alumina  in  the  vapor  of  boron  trichloride.  Fremy  prepared  it 
by  heating  fluoride  of  aluminium  with  boric  acid.  Ebelman 
also  obtained  it  by  heating  a  mixture  of  alumina  and  borax  to 
whiteness ;  under  these  conditions  crystals  of  corundum  were 
formed  at  the  same  time. 

By  precipitating  a  cold  solution  of  alum  with  sodium  borate, 
double  salts  are  obtained  containing  soda,  but  which  leave  on 
washing  with  warm  water  two  compounds  having  the  formulae 
2A12O3.BO3.5H2O  and  3A12O3.2BO3.8H2O.  If  the  washing  is 
prolonged  too  far  the  two  salts  are  completely  decomposed, 
leaving  a  residue  of  pure  alumina. 

ALUMINIUM  SILICATES. 

Compounds  of  alumina  and  silica,  or  aluminium,  silicon,  and 
oxygen  are  of  wide  occurrence  in  nature.  In  them  these  bases 


104  ALUMINIUM. 

occur  in  many  proportions ;  the  following  proportions  of  alumina 
to  silica,  A12O3  to  SiO2,  have  been  observed:  2-1,  3-2,  1-1, 
2-3,  1-2,  1-3,  1-4,  1-8,  thus  varying  from  tri-basic  silicates  to 
pent-acid  silicates.  Some  are  anhydrous,  others  hydrous;  in 
many  of  these  silicates  ferric  oxide  replaces  varying  quantities 
of  alumina  and  an  immense  number  of  silicates  are  known 
containing  other  metallic  bases  besides  aluminium.  These  by 
their  various  combinations  form  the  basis  of  most  rocks. 

APO3.SiO2,  or  APSiO5,  occurs  in  nature  as  Disthene,  Andalusite, 
and  Fibrolite.  They  are  not  attacked  by  acids,  are  infusible 
before  the  blowpipe,  specific  gravity  3  to  3.5,  and  hardness 
about  that  of  quartz. 

Al2O3.2SiO2.2H2O  or  Al2Si2O7  +  2H2O  forms  kaolin  or  white 
china  clay,  and  mixed  with  various  impurities  forms  the  basis 
of  many  common  clays.  It  is  produced  mostly  from  orthoclase,  a 
feldspar  containing  silica,  alumina,  and  potash,  by  the  decompos- 
ing influence  of  the  atmosphere.  The  moisture  and  carbonic 
acid  of  the  air  produce  the  following  reaction — 

K2A12S16O16  +  2H2O  +  CO2  =  Al2Si2O7.2H2O  +  K2CO3  4-  4SiO2. 

Kaolin  acquires  a  certain  plasticity  when  mixed  with  water. 
Hydrochloric  or  nitric  acids  have  no  action  on  it,  but  cold  sul- 
phuric acid  dissolves  its  alumina  setting  the  silica  at  liberty. 
It  is  infusible  unless  contaminated  with  particles  of  feldspar  or 
calcium  sulphate,  carbonate,  or  phosphate.  The  specific  gravity  of 
kaolin  is  2.3.  If  fused  with  six  times  its  weight  of  caustic  potash 
the  resulting  mass  gives  up  potassium  aluminate  when  washed 
with  water.  An  analogous  result  is  obtained  with  sodium  carbon- 
ate. Pure  kaolin  with  the  formula  Al2Si2O7.2H2O  contains 
39.4  per  cent,  of  alumina  or  20.9  per  cent,  of  aluminium ;  if  it 
is  calcined  enough  to  drive  off  the  water,  the  residue  will  con- 
tain 45.9  per  cent,  of  alumina  or  24.3  per  cent,  of  aluminium. 

Common  clays  contain  from  50  to  70  per  cent,  of  silica  and 
15  to  35  per  cent,  of  alumina,  and  are  not  often  amenable  to 
a  formula.  Two  of  somewhat  constant  composition  have  been 
given  the  formula  Al2O3.3SiO2.4H2O  and  Al2O3.5SiO2.3H2O. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  105 


CHAPTER  VI. 

PREPARATION  OF  ALUMINIUM  COMPOUNDS  FOR  REDUCTION. 

WE  will  consider  this  division  under  four  heads  : — 

I.  Alumina. 
II.  Aluminium  chloride  and  aluminium -sodium  chloride. 

III.  Aluminium  fluoride  and  aluminium-sodium  fluoride. 

IV.  Aluminium  sulphide. 

I. 

THE  PREPARATION  OF  ALUMINA. 
We  will  treat  this  subject  in  three  divisions  : — 

1.  From  Aluminium  Sulphate  or  Alums. 

2.  From  Beauxite. 

3.  From  Cryolite. 

1.  PREPARATION  OF  ALUMINA  FROM  ALUMS  OR  ALUMINIUM 

SULPHATE. 

Hydrated  alumina  can  be  precipitated  from  a  solution  of  any 
aluminium  salt  by  ammonium  hydrate,  an  excess  of  which  re-dis- 
solves a  portion.  Its  chemical  formula  is  ordinarily  written  APO3.- 
3H2O  or  AP(OH)6.  The  aluminium  hydrate  thus  precipitated  is  a 
pure  white,  very  voluminous,  almost  pasty  mass,  very  hard  to  wash. 
By  boiling  and  washing  with  boiling  water  it  becomes  more 
dense,  but  always  remains  very  voluminous.  Washing  on  a  fil- 
ter with  a  suction  apparatus  gives  the  best  results.  At  a  freezing 
temperature  this  hydrate  changes  into  a  dense  powder  which  is 
more  easily  washed.  On  drying  it  shrinks  very  much  in  volume 
and  forms  dense,  white  pieces,  transparent  on  the  edges.  When 
dried  at  ordinary  temperatures  it  has  the  composition  A12O3.H2O. 


106  ALUMINIUM. 

On  ignition,  the  other  molecule  of  water  is  driven  off,  leaving  an- 
hydrous alumina.  After  gentle  ignition  it  remains  highly  hygro- 
scopic, and  in  a  very  short  time  will  take  up  from  the  air  15  per 
cent,  of  water.  In  this  condition  it  is  easily  soluble  in  hydrochloric  or 
sulphuric  acid.  On  stronger  ignition  it  becomes  harder  and  soluble 
only  with  difficulty  in  concentrated  acid  ;  after  ignition  at  a  high 
temperature  it  is  insoluble,  and  can  only  be  brought  into  solution 
again  by  powdering  finely  and  fusing  with  potassium  acid-sul- 
phate or  alkaline  carbonate.  At  ordinary  furnace  temperatures 
alumina  does  not  melt,  but  in  the  oxy-hydrogen  blow-pipe  or 
the  electric  arc  it  fuses  to  a  limpid  liquid  and  appears  crystalline 
on  cooling. 

The  precipitation  in  aqueous  solution  and  subsequent  ignition 
is  not  economical  enough  to  be  practised  on  a  large  scale,  and  for 
industrial  purposes  the  aluminium  sulphate  or  alum  is  ignited 
directly.  About  the  easiest  way  to  proceed  is  to  take  ammonia 
alum  crystals,  put  them  into  a  clean  iron  pan  and  heat  gently,  when 
the  salt  melts  in  its  water  of  crystallization.  When  the  water 
has  evaporated,  a  brittle,  shining,  sticky  mass  remains,  which  on 
further  heating  swells  up  and  decomposes  into  a  dry,  white 
powder.  This  is  let  cool,  powdered,  put  into  a  crucible  and  heated 
to  bright  redness.  All  the  ammonia  and  almost  all  the  sulphuric 
acid  are  thus  removed.  The  rest  of  the  acid  can  be  removed  by 
moistening  the  mass  with  a  solution  of  sodium  carbonate,  drying 
and  again  igniting  ;  on  washing  with  water  the  acid  is  removed 
as  sodium  sulphate.  The  residue,  however,  will  contain  some 
caustic  soda,  which  for  its  further  use  in  making  aluminium  chlor- 
ide is  not  harmful.  Potash  alum  can  be  treated  in  a  similar  way, 
the  potassium  sulphate  being  washed  away  after  the  first  igni- 
tion. Still  more  easily  and  cheaply  can  alumina  be  made  by  ignit- 
ing a  mixture  of  4  parts  aluminium  sulphate  and  1  of  sodium 
carbonate.  On  washing,  sodium  sulphate  is  removed  from  the  alu- 
mina.* 

Deville  used  the  following  method  at  Javel :  Ammonia  alum 
or  even  the  impure  commercial  aluminium  sulphate  was  calcined, 
the  residue  appearing  to  be  pure,  white  alumina,  but  it  still  con- 

*  Kerl  and  Stohraan,  4th  Ed.  p.  739. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  107 

tained  sulphuric  acid,  potassium  sulphate,  and  a  notable  propor- 
tion of  iron.  This  alumina  is  very  friable,  and  is  passed  through 
a  fine  sieve  and  put  into  an  iron  pot  with  twice  its  weight 
of  solution  of  caustic  soda  of  45  degrees.  It  is  then  boiled  and 
evaporated,  and  the  alumina  dissolves  even  though  it  has  been 
strongly  calcined.  The  aluminate  of  soda  produced  is  taken  up 
in  a  large  quantity  of  water,  and  if  it  does  not  show  clear  im- 
mediately a  little  sulphuretted  hydrogen  is  passed  in,  which 
hastens  the  precipitation  of  the  iron.  The  liquor  is  let  stand,  the 
clear  solution  decanted  off  and  subjected  while  still  warm  to  the 
action  of  a  stream  of  carbonic  acid  gas.  This  converts  the  soda 
into  carbonate  and  precipitates  the  alumina  in  a  particularly 
dense  form  which  collects  in  a  space  not  one-twentieth  of  the 
volume  which  would  be  taken  up  by  gelatinous  alumina.  This 
precipitate  is  best  washed  by  decantation,  but  a  large  number  of 
washings  are  necessary  to  remove  all  the  sodium  carbonate  from 
it ;  it  is  even  well,  before  finishing  the  washing,  to  add  a  little  sal- 
ammoniac  to  the  wash-water  in  order  to  hasten  the  removal  of 
the  soda.  The  well-dried  alumina  is  calcined  at  a  red  heat. 

*Tilghman  decomposes  commercial  sulphate  of  alumina,  Al2- 
(SO4)3.18H2O,  by  filling  a  red-hot  fire-clay  cylinder  with  it.  This 
cylinder  is  lined  inside  with  a  magnesia  fettling,  is  kept  at  a  red 
heat,  the  sulphate  put  in  in  large  lumps,  and  steam  is  passed 
through  the  retort,  carrying  with  it  vapor  of  sodium  chloride. 
This  last  arrangement  is  effected  by  passing  steam  into  a  cast-iron 
retort  in  which  the  salt  named  is  kept  melted,  and  as  the  steam 
leaves  this  retort  it  carries  vapor  of  the  salt  with  it.  It  is  pref- 
erable, however,  to  make  a  paste  of  the  sulphate  of  alumina  and 
the  sodium  chloride,  forming  it  into  small  hollow  cylinders,  which 
are  well  dried,  and  then  the  fire-clay  cylinder  filled  with  these. 
Then,  the  cylinder  being  heated  to  whiteness,  highly  superheated 
steam  is  passed  over  it.  The  hydrochloric  acid  gas  which  is 
formed  is  caught  in  a  condensing  apparatus,  and  there  remains  a 
mass  of  aluminate  of  soda,  which  is  moistened  with  water  and 
treated  with  a  current  of  carbon  dioxide  and  steam.  By  washing 

*  Mierzinski. 


108  ALUMINIUM. 

the  mass,  the  soda  goes  into  solution  and  hydrated  alumina  re- 
mains, which  is  washed  well  and  is  ready  for  use. 

Mr.  Webster's  process  for  making  pure  alumina  at  a  low  price 
is  now  incorporated  as  a  part  of  the  Aluminium  Co.  Ld.'s  pro- 
cesses, but  whether  it  is  that  there  have  been  no  advances  made 
in  this  line  during  the  past  few  years  or  that  valuable  advances 
have  been  made  but  are  sedulously  kept  secret,  I  am  unable  to 
say.  The  late  descriptions  of  the  Deville-Castner  processes  all 
commence  with  the  sentiment :  In  the  beginning  we  have  alu- 
minium hydrate.  Such  being  the  case,  the  only  description  we 
can  give  of  Webster's  process  is  one  dated  1883. 

*Three  parts  of  potash  alum  are  mixed  with  one  part  of  pitch, 
placed  in  a  calcining  furnace  and  heated  to  200°  or  250°.  About 
40  per  cent,  of  water  is  thus  driven  off,  leaving  sulphate  of  pot- 
ash and  aluminium,  with  some  ferric  oxide.  After  heating  about 
three  hours,  the  pasty  mass  is  taken  out,  spread  on  a  stone  floor 
and  when  cold  broken  to  pieces.  Hydrochloric  acid  (20  to  25 
per  cent.)  is  poured  upon  these  pieces,  placed  in  piles,  which  are 
turned  over  from  time  to  time.  When  the  evolution  of  sulphu- 
retted hydrogen  has  stopped ,  about  five  per  cent,  of  charcoal- 
powder  or  lampblack,  with  enough  water  to  make  a  thick  paste, 
is  added.  The  mass  is  thoroughly  broken  up  and  mixed  in  a  mill, 
and  then  worked  into  balls  of  about  a  pound  each.  These  are 
bored  through  to  facilitate  drying,  and  heated  in  a  drying  chamber 
at  first  to  40°,  then  in  a  furnace  from  95°  up  to  150°.  The  balls 
are  then  kept  for  three  hours  at  a  low  red  heat  in  retorts  while  a 
mixture  of  two  parts  steam  and  one  part  air  is  passed  through,  so 
that  the  sulphur  and  carbon  are  converted  into  sulphurous  oxide 
and  carbonic  oxide,  and  thus  escape.  The  current  of  gas  carries 
over  some  potassium  sulphate,  ferrous  sulphate,  and  alumina,  and 
is  therefore  passed  through  clay  condensers. 

The  residue  in  the  retorts  consists  of  alumina  and  potassium 
sulphate ;  it  is  removed,  ground  to  fine  powder  in  a  mill,  treated 
with  about  seven  times  its  weight  of  water,  boiled  in  a  pan  or 
boiler  by  means  of  steam  for  about  one  hour,  then  allowed  to 
stand  till  cool.  The  solution  containing  the  potassium  sulphate 

*  Austrian  Patent,  Sept.  28,  1882  ;  English  patent,  No.  2580,  1881.  Ding- 
ier, 1883,  vol.  259,  p.  86. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  109 

is  run  off  and  evaporated  to  dryness,  the  alumina  is  washed  and 
dried.  The  potassium  sulphate,  as  a  by-product,  is  said  to  pay 
one-half  the  cost  of  the  process. 

This  deposit  contains  about  84  per  cent,  of  alumina,  while  that 
obtained  by  the  old  process  of  precipitation  has  only  65  per  cent. 
Thus  a  large  saving  is  effected  in  cost  and  19  per  cent,  more  alu- 
mina is  obtained.  In  addition  to  this,  the  whole  of  the  by-pro- 
ducts are  recovered,  consisting  of  potassium  sulphate,  sulphur 
(which  is  used  in  making  sulphuric  acid),  and  aluminate  of  iron. 

2.  PREPAEATION  OF  ALUMINA  FROM  BEAUXITE. 

At  Salindres,  the  alumina  used  in  the  Deville  process  is  ob- 
tained from  beauxite  by  the  following  processes,  which  are  in 
general  use  for  extracting  pure  alumina  from  this  mineral.* 
Beauxite  is  plentiful  enough  in  the  south  of  France,  principally 
in  the  departments  of  Herault,  Bouches-du-Khone,  and  Var.  It 
contains  at  least  seventy-five  per  cent,  alumina.  To  separate  the 
alumina  from  ferric  oxide,  it  is  treated  with  carbonate  of  soda, 
under  the  influence  of  a  sufficiently  high  temperature,  the  alumina 
displacing  the  carbonic  acid  and  forming  an  aluminate  of  soda, 
APO3.3Na2O,  while  the  ferric  oxide  remains  unattacked.  A  simple 
washing  with  water  then  permits  the  separation  of  the  former 
from  the  insoluble  ferric  oxide.  The  beauxite  is  first  finely  pul- 
verized by  means  of  a  vertical  mill-stone,  then  intimately  mixed 
with  some  sodium  carbonate.  The  mixture  is  made,  for  one  opera- 
tion, of — 

480  kilos,  beauxite. 

300     "       sodium  carbonate  of  90  alkali  degrees. 

This  mixture  is  introduced  into  a  reverberatory  furnace,  resem- 
bling in  form  a  soda  furnace,  and  which  will  bear  heating  strongly. 
The  mass  is  stirred  from  time  to  time,  and  it  is  kept  heated  until 
all  the  carbonate  has  been  attacked,  which  is  recognized  by  a  test 
being  taken  which  does  not  effervesce  with  acids.  The  operation 
lasts  from  five  to  six  hours. 

The  aluminate  thus  obtained  is  separated  from  ferric  oxide  by 
a  washing  with  warm  water.  This  washing  is  made  at  first  with 

*  Fremy's  Ency.  Chimique. 


110 


ALUMINIUM. 


a  feeble  solution  which  has  served  for  the  complete  exhaustion  of 
the  preceding  charge,  which  was  last  washed  with  pure  water, 
forming  thus  this  feeble  solution.  This  gives,  on  the  first  leach- 
ing, solutions  of  aluminate  concentrated  enough  to  be  called  strong 
liquor,  which  are  next  treated  by  the  current  of  carbonic  acid  gas 
to  precipitate  the  hydrated  alumina.  The  charge  is  next  washed 
with  pure  water,  which  completely  removes  the  aluminate ;  this 
solution  is  the  weak  liquor,  wrhich  is  put  aside  in  a  special  tank, 
and  used  as  the  first  leaching  liquor  on  the  next  charge  treated. 
This  treatment  takes  place  in  the  following  apparatus  (see  Fig. 
1)  :  B  is  a  sheet-iron  vessel,  in  the  middle  of  which  is  a  metallic 


Fig.  1, 
B 


1-f.vYTfpe  o 


grating,  F,  on  which  is  held  all  round  its  edges,  by  pins,  a  cloth, 
serving  as  a  filter.  The  upper  part  of  this  vessel  is  called  sim- 
ply the  filter.  A  ought  to  be  closed  by  a  metallic  lid  held  on 
firmly  by  bolts.  To  work  the  apparatus,  about  500  kilos  of  the 


PREPARATION    OF   ALUMINIUM   COMPOUNDS.  Ill 

charge  to  be  washed  is  placed  on  the  filter  cloth,  the  lid  is  closed, 
then  the  steam-cock  /  of  the  reservoir  A  is  opened.  In  A  is  the 
weak  solution  from  the  last  washing  of  the  preceding  charge. 
The  pressure  of  the  steam  makes  it  rise  by  the  tube  T  into  the 
filter;  another  jet  of  steam,  admitted  by  the  cock  6,  rapidly 
warms  the  feeble  liquor  as  it  soaks  into  the  charge.  After  filter- 
ing through,  the  strong  liquor  is  drawn  off  by  turning  the  stop- 
cock G.  The  weak  solution  of  the  reservoir  A  is  put  into  the 
filter  in  successive  portions,  and  not  all  at  once ;  and  after  each 
addition  of  solution  has  filtered  through,  its  strength  in  B.°  is 
taken,  before  any  more  solution  is  run  in  ;  then,  when  the  solu- 
tion marks  3°  to  4°,  it  is  placed  in  a  special  tank  for  weak  liquor, 
with  all  that  comes  through  afterwards.  Just  about  this  time, 
the  weak  liquor  of  the  reservoir  A  is  generally  all  used  up,  and 
is  replaced  by  pure  water  introduced  by  the  tube  d.  All  the  solu- 
tions which  filtered  through,  marking  over  3°  to  4°  B.,  are  put 
together,  and  form  the  strong  liquor  which  marks  about  12°  B. 
This  extraction  of  the  aluminate  being  completed  by  the  pure 
water,  the  residue  on  the  filter  is  taken  out,  and  a  new  operation 
may  be  commenced. 

The  strong  liquor  is  introduced  into  a  vessel  having  an  agita- 
tor, where  a  strong  current  of  carbonic  acid  gas  may  precipitate 
the  alumina  from  it.  The  gas  is  produced  by  small  streams  of 
hydrochloric  acid  continuously  falling  on  some  limestone  con- 
tained in  a  series  of  earthenware  jars.  The  precipitation  vessel  is 
called  a  baratte.  The  carbonic  acid  after  having  passed  through 
a  washing  flask,  is  directed  to  a  battery  of  three  barattes,  where 
the  precipitation  is  worked  methodically,  so  as  to  precipitate  com- 
pletely the  alumina  of  each  baratte,  and  utilize  at  the  same  time  all 
the  carbon  dioxide  produced.  In  order  to  do  this,  the  gas  always 
enters  first  into  a  baratte  in  which  the  precipitation  is  nearest 
completion,  and  arrives  at  last  to  that  in  which  the  solution  is 
freshest.  When  the  gas  is  not  all  absorbed  in  the  last  baratte, 
the  first  is  emptied,  for  the  precipitation  in  it  is  then  completed, 
and  it  is  made  the  last  of  the  series,  the  current  being  now  directed 
first  into  the  baratte  which  was  previously  second,  while  the 
newly  charged  one  is  made  the  last  of  the  series.  The  process  is 
thus  kept  on  continuously.  The  apparatus  used  is  shown  in  Fig.  2. 


112 


ALUMINIUM. 


Each  baratte  holds  about  1200  litres  of  solution,  and  the  complete 
precipitation  of  all  the  alumina  in  it  takes  five  to  six  hours.     A 
mechanical  agitator  stirs  the  contents  continually,  and  a  current 
of  steam  is  let  into  the  double  bottom  so  as  to  keep  the  tempera- 
Fig.  2. 


a.  Charging  pipe.  6.  Steam  pipe.  c.  Steam  drip.  d.  CO2  enters.  /.  Discharge 
pipe.  A.  Agitator,  made  of  iron  rods.  (7.  Tank  in  which  the  precipitate  settles. 
B.  "Baratte  body.  D.  Steam  jacket. 

ture  of  the  solution  about  70°.  The  precipitated  alumina  and  the 
solution  of  sodium  carbonate  which  remain  are  received  in  a  vat 
placed  beneath  each  baratte.  The  solution  is  decanted  off  clear, 
after  standing,  and  then  evaporated  down  to  dry  ness,  regenerating 
the  sodium  carbonate  used  in  treating  the  beaux  ite  to  make  the 
alumiuate,  less  the  inevitable  losses  inseparable  from  all  indus- 
trial operations.  The  deposit  of  alumina  is  put  into  a  conical 
strainer  to  drain,  or  else  into  a  centrifugal  drying  machine,  which 
rapidly  drives  out  of  the  hydrated  alumina  the  solution  of  sodium 
carbonate  which  impregnates  it ;  a  washing  with  pure  water  in 
the  drier  itself  terminates  the  preparation  of  the  alumina.  At 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  113 

the  works  at  Salindres,  a  part  of  this  alumina  is  converted  into 
sulphate  of  alumina,  which  is  sold,  the  remainder  being  used  for 
the  aluminium  manufacture.  After  washing  in  the  dryer,  the 
alumina  presents  this  composition  : — 

Alumina         .......     47.5 

Water    .         .         .         .         .         .         .          .     50.0 

Sodium  carbonate  .         .         .         .         .       2.5 

Behnke*  produces  alumina  by  igniting  beauxite  or  a  similar 
mineral  with  sodium  sulphate,  carbon,  and  ferric  oxide,  using  for 
each  equivalent  of  alumina  present  at  least  one  equivalent  of 
alkali  and  one-half  an  equivalent  of  ferric  oxide.  The  mixture 
is  heated  in  a  muffle  or  reverberatory  furnace.  The  fritted  prod- 
uct is  ground,  exposed  to  the  air,  and  washed  with  water.  Sod- 
ium aluminate  goes  into  solution  along  with  some  sodium  sul- 
phate, while  ferrous  sulphide  and  undecomposed  material  remains 
as  a  residue.  By  passing  carbonic  acid  gas  or  gases  from  com- 
bustion through  the  solution,  the  alumina  is  precipitated.  The 
residue  spoken  of  is  roasted,  the  sulphurous  oxide  given  off 
utilized,  and  the  residue  used  over  in  place  of  fresh  ferric  oxide. 

R.  Lieberf  proposes  to  treat  beauxite,  aluminous  iron  ore,  etc. 
in  a  somewhat  similar  way.  These  materials  are  to  be  ground 
fine,  mixed  with  sodium  chloride  and  magnesium  sulphate  (Kieser- 
ite),  moistened  with  water,  and  pressed  into  bricks  or  balls. 
These  are  dried  and  put  into  a  retort  heated  red-hot  by  generator 
gas.  Hydrochloric  acid  gas  is  first  given  off4,  sodium  sulphate 
and  magnesium  chloride  being  formed.  In  a  further  stage  of  the 
process  sulphurous  oxide  is  evolved,  the  alumina  reacting  on  the 
sodium  sulphate  to  form  sodium  aluminate.  The  latter  is  washed 
out  of  the  residue,  and  its  alumina  precipitated  by  the  ordinary 
methods. 

H.  MullerJ  proposes  to  extract  the  alumina  from  silicates  con- 
taining it  by  mixing  them  with  limestone,  dolomite,  or  magnesite, 
also  with  alkali  caustic,  carbonate,  or  sulphate  (in  the  last  case 
also  with  carbon),  and  heating  the  mixture  to  bright-redness. 

*  German  Patent  (D.  R.  P.),  No.  7256. 
f  German  Patent  (D.  R.  P.),  No.  5670. 
|  German  Patent  (D.  R.  P.),  No.  12,947. 


114  ALUMINIUM. 

Alkaline  aluminate  is  washed  out  of  the  resulting  mass,  while  the 
residue,  consisting  of  lime,  magnesia,  iron  oxide,  etc.,  is  mixed 
with  water-glass  and  moulded  into  artificial  stone. 

Common  salt  is  said  not  to  react  on  beauxite  if  fused  with  it 
alone,  but  will  decompose  it  if  steam  is  used.  Tilghman*  first 
used  this  reaction  in  1847.  It  is  said  that  it  was  also  used  at 
Nanterre  and  Salindres  previously  to  1865.  A  mixture  of  sodium 
chloride  and  beauxite  was  treated  in  a  closed  retort  and  steam 
passed  through,  or,  better,  in  a  reverberatory  furnace  and  steam 
passed  over  it,  at  a  high  temperature.  Much  sodium  chloride 
must  have  been  lost  by  the  latter  arrangement.  The  fused  mass 
was  treated  with  water,  when  sodium  aluminate  dissolved  out. 

R.  Wagnerf  proposed  to  make  a  solution  of  sodium  sulphide, 
by  reducing  sodium  sulphate  by  carbon  bisulphide,  and  to  boil 
the  beauxite  in  it.  The  sulphuretted  hydrogen  evolved  was  to 
be  absorbed  by  ferric  hydrate ;  while  the  sodium  aluminate  was 
converted  into  soda  and  alumina  by  any  of  the  ordinary  methods. 

According  to  Lowig's  experiments,  solution  of  sodium  alu- 
minate can  be  precipitated  by  calcium,  barium,  strontium,  or 
magnesium  hydrates,  forming  caustic  soda  and  hydrated  alumina, 
the  latter  being  precipitated,  together  with  lime,  baryta,  strontia, 
or  magnesia.  The  precipitate  is  washed  by  decantation  and  then 
divided  into  two  portions,  one  of  which  is  dissolved  in  hydro- 
chloric acid,  the  other  made  into  a  mush  with  water  and  gradually 
added  to  the  solution  of  the  first  half  until  the  filtrate  shows  only 
a  very  little  alumina  in  solution.  Chloride  of  calcium,  barium, 
strontium,  or  magnesium  has  been  formed,  and  the  alumina  all 
precipitated. 

Dr.  K.  J.  Bayer  has  made  an  improvement  in  the  process  of 
extracting  alumina  from  beauxite,  which  has  received  great  com- 
mendation from  those  directly  interested  in  the  business,  and  who 
may  be  supposed  to  have  proved  its  merits.  Dr.  Bayer  thus 
describes  it  :J  Beauxite  is  fused  with  sodium  carbonate  or  sul- 
phate, and  the  solution  obtained  by  washing,  containing  sodium 

*  Polytechnisehes  Journal,  106,  p.  196. 
f  Wagner's  Jahresb.,  1865,  p.  332. 
t  Stahl  und  Eisen,  Feb.  1889,  p.  112. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  115 

aluminate,  is  not  decomposed  by  carbonic  acid  as  formerly,  but 
by  the  addition  of  aluminium  hydrate  with  constant  stirring. 
The  decomposition  of  the  solution  goes  on  until  the  quantity  of 
alumina  remaining  in  solution  is  to  the  sodium  protoxide  as 
1  to  6.  This  precipitation  takes  place  in  the  cold,  and  the  pul- 
verulent aluminium  hydrate  separated  out  is  easily  soluble  in 
acids.  The  alkaline  solution  remaining  is  concentrated  by  evap- 
oration, taken  up  by  ground  beauxite,  dried,  calcined,  and  melted, 
and  thus  goes  through  the  process  again.  The  use  of  this  caustic 
soda  solution  containing  alumina  is  thus  much  more  profitable 
than  using  soda,  because  by  using  the  latter  only  75  per  cent,  of 
the  beauxite  used  is  utilized,  whereas  by  the  former  all  the  alu- 
mina dissolved  by  the  solution  is  obtained  again. 

3.  PREPARATION  OF  ALUMINA  FROM  CRYOLITE. 

By  the  dry  way.  —  The  following  method  was  invented  by 
Julius  Thomson ;  the  description  is  taken  principally  from  Mier- 
zinski's  "Fabrikation  des  Aluminiums:"  The  cryolite  is  pul- 
verized, an  easy  operation,  and  to  every  100  parts,  130  to  150 
parts  of  chalk  are  added,  and  a  suitable  quantity  of  fluorspar  is 
also  used,  which  remains  in  the  residue  on  washing  after  ignition. 
More  chalk  is  used  than  is  theoretically  necessary,  in  order  to 
make  the  mass  less  fusible  and  keep  it  porous.  But,  to  avoid 
using  too  much  chalk  merely  for  this  purpose,  a  certain  quantity 
of  coke  may  be  put  into  the  mixture.  It  is  of  the  first  im- 
portance that  the  mixture  be  very  intimate  and  finely  pulverized. 
It  is  of  greater  importance  that  the  mixture  be  subjected  to  just 
the  proper  well-regulated  temperature  while  being  calcined. 
The  cryolite  will  melt  very  easily,  but  this  is  to  be  avoided.  On 
this  account,  the  calcination  cannot  take  place  in  an  ordinary 
smelting  furnace,  because,  in  spite  of  stirring,  the  mass  will  melt  at 
one  place  or  another,  while  at  another  part  of  the  hearth  it  is  not 
even  decomposed,  because  the  heat  at  the  fire-bridge  is  so  much 
higher  than  at  the  farther  end  of  the  hearth.  Thomson  con- 
structed a  furnace  for  this  special  purpose  (see  Figs.  3  and  4),  in 
which  the  flame  from  the  fire  first  went  under  the  bed  of  the  fur- 
nace, then  over  the  charge  spread  out  on  the  bed,  and  finally  in 


116 


ALUMINIUM. 


a  flue  over  the  roof  of  the  hearth..    The  hearth  has  an  area  of 
nearly  9  square  metres,  being  4  metres  long  and  2.5  metres  wide. 


It  is  charged  twelve  times  each  day,  each  time  with  500  kilos  of 
mixture,  thus  roasting  6000  kilos  daily,  with  a  consumption  of 
800  kilos  of  coal.  The  waste  heat  of  the  gases  escaping  from 

Fig.  4. 


the  furnace  is  utilized  for  drying  the  soda  solution  to  its  crystal- 
lizing point,  and  the  gases  finally  pass  under  an  iron  plate  on 
which  the  chalk  is  dried.  In  this  furnace  the  mass  is  ignited 
thoroughly  without  a  bit  of  it  melting,  so  that  the  residue  can  be 
fully  washed  with  water. 

The  decomposition  takes  place  according  to  the  formula — 
Al2F6.6NaF  +  6CaCO3  -  Al203.3Na2O  +  6CaF2  +  6CO2, 
the  resultant  product  containing  aluminate  of  soda,  soluble  in 


PREPARATION    OF   ALUMINIUM    COMPOUNDS.  117 

water,  and  insoluble  calcium  fluoride.  The  reaction  commences  at  a 
gentle  heat,  but  is  not  completed  until  a  red  heat  is  reached.  Here 
is  the  critical  point  of  the  whole  process,  since  a  very  little  raising 
of  the  temperature  above  a  red  heat  causes  it  to  melt.  However, 
it  must  not  be  understood  that  the  forming  of  lumps  is  altogether 
to  be  avoided.  These  lumps  would  be  very  hard  and  unwork- 
able when  cold,  but  they  can  be  broken  up  easily  while  hot,  so 
that  they  may  be  drawn  out  of  the  furnace  a  few  minutes  before 
the  rest  of  the  charge  is  removed,  and  broken  up  while  still  hot 
without  any  trouble.  The  whole  charge,  on  being  taken  out,  is 
cooled  and  sieved,  the  hard  lumps  which  will  not  pass  the  sieve 
are  ground  in  a  mill  and  again  feebly  ignited,  when  they  will 
become  porous  and  may  be  easily  ground  up.  However,  the 
formation  of  these  lumps  can  be  avoided  by  industrious  stirring 
of  the  charge  in  the  furnace.  A  well-calcined  mixture  is  porous, 
without  dust  and  without  lumps  which  are  too  hard  to  be  crushed 
between  the  fingers.  We  would  here  remark  that  mechanical 
furnaces  of  similar  construction  to  those  used  in  the  manufacture 
of  soda,  potash,  sulphate  of  soda,  etc.,  are  more  reliable  and  give 
the  best  results  if  used  for  this  calcination.  The  mixture,  or 
ashes,  as  the  workmen  call  it,  is  drawn  still  hot,  and  washed 
while  warm  in  conical  wooden  boxes  with  double  bottoms,  or  the 
box  may  have  but  one  bottom,  with  an  iron  plate  about  76  milli- 
metres above  it.  A  series  of  such  boxes,  or  a  large  apparatus 
having  several  compartments,  may  be  so  arranged  that  the  wash- 
ing is  done  methodically,  i.  e.,  the  fresh  water  comes  first  in  con- 
tact with  a  residue  which  is  already  washed  nearly  clean,  and  the 
fresh  charge  is  washed  by  the  strong  liquor.  This  is  known  as 
the  "  Lessiveur  rnethodique,"  and  an  apparatus  constructed  espe- 
cially for  this  purpose  is  described  in  Dingier  186,  376,  by  P.  J. 
Havrez,  but  the  subject  is  too  general  and  the  description  too 
long  to  be  given  here.  A  very  suitable  washing  apparatus  is  also 
that  of  Schank,  used  in  the  soda  industry  for  washing  crude  soda, 
and  described  in  "  Lunge's  Handbook  of  the  Soda  Industry," 
Book  II.  p.  410.  Since  the  ashes  are  taken  warm  from  the  fur- 
nace the  washing  water  need  not  be  previously  heated,  but  the 
final  wash-water  must  be  warmed,  as  the  ashes  have  been  cooled 
down  by  the  previous  washings.  As  soon  as  the  strong  liquor 


118  ALUMINIUM. 

does  not  possess  a  certain  strength,  say  20°  B.,  it  is  run  over  a 
fresh  charge  and  so  brought  up.  The  solution  contains  sodium 
aluminate. 

The  carbon  dioxide  necessary  for  precipitating  the  hydrated 
alumina  may  be  made  in  different  ways.  The  gases  coming  from 
the  furnace  in  calcining  the  cryolite  might  be  used  if  they  were 
not  contaminated  with  dust ;  and  there  is  also  the  difficulty  that 
exhausting  the  gases  from  the  furnace  would  interfere  with  the 
calcination.  It  has  also  been  recommended  to  use  the  gases  from 
the  fires  under  the  evaporating  pans,  by  exhausting  the  air  from 
the  flues  and  purifying  it  by  washing  with  water.  This  can  only 
be  done  where  the  pans  are  fired  with  wood  or  gas.  However, 
the  lime-kiln  is  almost  exclusively  used  to  furnish  this  gas.  The 
kiln  used  is  shaped  like  a  small  blast  furnace.  Leading  in  at  the 
boshes  are  two  flues  from  five  fire-places  built  in  the  brickwork 
of  the  furnace,  and  the  heat  from  these  calcines  the  limestone. 
The  gases  are  taken  off  by  a  cast-iron  down-take  at  the  top.  At' 
the  bottom  of  the  furnace,  corresponding  with  the  tap  hole  in  a 
blast  furnace,  is  an  opening,  kept  closed,  from  which  lime  is  with- 
drawn at  intervals.  A  strong  blast  is  blown  in  just  above  the 
entrance  of  the  side  flues,  and  by  keeping  up  a  pressure  in  the 
furnace,  leakings  into  it  may  be  avoided.  The  gas  is  sucked 
away  from  the  top  by  a  pump,  which  forces  it  through  a  cleaning 
apparatus  constructed  like  a  wash-bottle,  and  it  is  then  stored  in 
a  gasometer.  Instead  of  the  pump,  a  steam  aspirator  may  be 
used,  which  is  always  cheaper  and  takes  up  less  room. 

The  precipitation  with  carbonic  acid  gas  is  made  by  simply 
forcing  it  through  a  tube  into  the  liquid.  The  apparatus  used  at 
Salindres  is  oue  of  the  most  improved  forms.  (See  p.  112.)  The 
precipitate  is  granular,  and  settles  easily.  However,  it  is  not  pure 
hydrated  alumina,  but  a  compound  of  alumina,  soda,  carbonic 
acid,  and  water,  containing  usually  about — 

Alumina 45  per  cent. 

Sodium  carbonate        .         .         .         .         .         .     20       " 

Water 35       " 

The  sodium  carbonate  can  be  separated  by  long-continued  boil- 
ing with  water,  but  by  this  treatment  the  alumina  becomes  very 
gelatinous  and  very  difficult  of  further  treatment.  The  precip- 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  119 

itate  was  formerly  separated  on  linen  filters,  but  centrifugal 
machines  are  now  preferred.  The  evaporated  solution  gives  a 
high  grade  of  carbonate  of  soda  free  from  iron.  The  heavy  resi- 
due which  is  left  after  the  ashes  have  been  lixiviated  consists  of 
calcium  fluoride  with  small  quantities  of  ferric  oxide,  lime,  un- 
decomposed  cryolite,  and  aluminate  of  soda,  and  has  not  been 
utilized  for  any  purpose. 

R.  Biederrnan*  states  that  if  steam  is  passed  over  molten  cryo- 
lite at  a  white  heat,  hydrofluoric  acid  gas  and  sodium  fluoride 
are  formed  and  driven  over,  while  a  white,  pure  crystalline  mass 
of  alumina  remains. 

Utilization  of  aluminous  fluoride  slags. — At  Nanterre,  DeviDe 
used  the  following  process  for  utilizing  in  one  operation  the  slags 
from  the  aluminium  manufacture  and  the  residues  from  the  so- 
dium manufacture. 

"  The  slags  from  making  aluminium  contain  60  per  cent,  of 
sodium  chloride  and  40  per  cent,  of  insoluble  matter;  the  former 
can  be  removed  by  a  single  washing.  The  insoluble  material  is 
almost  entirely  aluminium  fluoride,  with  a  little  alumina  and  un- 
clecomposed  cryolite.  When  fluorspar  is  used  as  a  flux,  the  sodium 
chloride  in  the  slag  is  in  part  replaced  by  calcium  chloride ;  but, 
in  general,  all  the  fluorine  in  the  slag  is  found  combined  with 
the  aluminium,  which  shows  the  great  affinity  between  these  two 
elements.  The  residues  left  in  the  sodium  retorts  deteriorate 
quickly  when  exposed  to  the  air,  and  contain  ordinarily,  according 
to  my  analysis — 

Carbon 20.0 

Carbonate  of  soda        .         .         .         .         .         .         .14.5 

Caustic  soda        ........       8.3 

Sulphate  of  soda 2.4 

Carbonates  of  lime  and  iron         .....     29.8 
Water 25.0 

100.0 

"To  utilize  these  two  materials,  5  to  6  parts  of  the  sodium 
residues  are  mixed  carefully  with  one  part  of  the  washed  slag, 
and  the  whole  calcined  at  a  red  heat.  The  fusion  becomes  pasty  ; 

*  Kerl  and  Stohman,  4th  Ed.,  p.  819. 


120  ALUMINIUM. 

it  is  cooled  and  washed,  when  aluminate  of  soda  goes  into  solu- 
tion and  on  treatment  with  carbon  dioxide  gives  sodium  carbonate 
and  alumina.  According  to  my  laboratory  experiments — 

1000  grammes  of  sodium  residues 
160         "         "  washed  slags 

have  given 

110         "         "  calcined  alumina 

225         "         "  dry  sodium  carbonate. 

"  The  residue  left  on  washing  the  fusion  weighs  about  one-half 
the  weight  of  the  soda  residues  used,  and  contains — 

Carbon         .         .         . 30.0 

Calcium  fluoride          .  .         .         .  •       .         .         .     32.0 

Alumina      .         .         .  .         .         .         .         .         .0.6 

Various  other  materials  ......     37.4 

"  The  latter  item  is  formed  of  ferric  oxide,  oxide  of  manganese, 
a  little  silica  and  some  oxysulphide  of  calcium.7' 

Decomposition  of  cryolite  in  the  wet  way. — Devi  lie  used  the  fol- 
lowing method  at  Javel,  which  he  thus  describes  : — 

"  In  the  Greenland  cryolite  there  are  to  be  found  numerous 
pieces  containing  siderite  (ferrous  carbonate).  It  is  necessary  to 
extract  all  these  pieces  before  using  the  mineral  as  a  flux  in  pro- 
ducing the  aluminium.  The  rejected  fragments  are  then  utilized 
by  pulverizing  them  finely,  mixing  with  about  three-fourths  of 
their  weight  of  pure,  burnt  lime  and  the  whole  carefully  slaked. 
After  the  slaking,  water  is  added  in  large  quantity,  and  the  ma- 
terial is  heated  in  a  large  cast-iron  vessel  by  means  of  a  steam- 
coil.  A  reaction  takes  place  at  once,  and  is  complete  if  the  pro- 
cess is  well  conducted.  Some  insoluble  aluminate  of  lime  may 
be  formed,  but  it  can  be  recovered  from  the  residue  by  digesting 
it  with  some  solution  of  carbonate  of  soda.  The  residue  re- 
maining is  calcium  fluoride,  which  settles  easily,  and  the  clear 
liquor  decanted  off  contains  aluminate  of  soda,  from  which 
alumina  can  be  precipitated  as  before.  The  calcined  alumina  ob- 
tained may  contain  iron  when  the  cryolite  used  contains  a  large 
amount  of  ferrous  carbonate.  It  has  appeared  to  me  that  the 
latter  mineral  may  be  decomposed  by  the  lime,  and  some  prot- 
oxide of  iron  be  thus  dissolved  by  the  soda  in  small  quantity. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  121 

"  We  make  alumina  by  this  method  at  Nanterre  only  because 
it  utilizes  the  impure  pieces  of  cryolite  and  works  in  conveniently 
with  the  previously-described  processes  for  utilizing  the  slags." 

An  ingenious  modification  of  the  above  process  was  devised  by 
Sauerwein.  The  first  reaction  is  the  same,  five  parts  of  finely- 
powdered  cryolite  being  boiled  with  four  parts  of  burnt  lime,  as 
free  as  possible  from  iron,  producing  a  solution  of  sodium  alumin- 
ate  and  a  residue  of  insoluble  calcium  fluoride.  Tissier  recom- 
mended using  two  parts  of  cryolite  to  one  of  lime,  but  with  these 
proportions  only  about  one-third  of  the  aluminium  in  the  cryolite 
is  converted  into  soluble  aluminate.  Hahn  claims  that  complete 
decomposition  takes  place  by  using  100  parts  of  cryolite  to  88 
parts  of  burnt  lime.  The  solution  is  settled,  washed  by  decan- 
tation,  and  these  washings  put  with  the  strong  solution  first 
poured  off;  the  next  wrashings  are  reserved  for  the  fresh  wash- 
water  of  another  operation.  The  solution  of  sodium  aluminate 
is  then  boiled  with  a  quantity  of  cryolite  equal  to  the  amount 
first  used,  when  sodium  fluoride  is  formed  and  alumina  precipi- 
tated. This  operation  is  in  no  way  difficult,  only  requiring  a 
little  more  attention  than  the  first.  The  alumina  thus  made  is 
very  finely  divided.  The  reactions  involved  are  : — 

Al2F6.61NaF  +  6CaO= Al2O3.3Na2O  +  6CaF2. 
Al2F6.6NaF  +  Al2O3.3Na2O  -f  6H2O==  2(A12O3.3H2O)  +  12NaF. 

During  this  last  operation  it  is  best  to  add  an  excess  of  cryo- 
lite, and  keep  the  liquid  in  motion  to  prevent  that  mineral  from 
caking  at  the  bottom.  Lead  is  the  best  material  to  make  these 
precipitating  tanks  of,  since  iron  would  contaminate  the  alumina. 
The  precipitate  is  washed  as  in  the  previous  operation.  The  so- 
lution of  sodium  fluoride  is  boiled  with  the  requisite  quantity  of 
burnt  lime,  which  converts  it  into  caustic  soda,  NaOH,  which  is 
separated  from  the  precipitated  calcium  fluoride  by  decantation 
and  washing. 

In  the  establishment  of  Weber,  at  Copenhagen,  where  at  one 
time  all  the  cryolite  produced  in  Greenland  was  received,  the 
mineral  was  decomposed  by  acid.  Hydrochloric  acid  attacks  the 
mineral  slowly,  but  sulphuric  acid  immediately  dissolves  the  sod- 
ium fluoride,  with  disengagement  of  hydrofluoric  acid ;  gelatin- 


122  ALUMINIUM. 

ous  aluminium  fluoride  separates  out  and  is  attacked  more  slowly. 
The  cryolite  requires  nearly  1J  parts  of  sulphuric  acid  to  dissolve 
it,  the  reaction  being  — 


The  solution  is  evaporated  and  crystallized,  when  the  sodium  sul- 
phate crystallizes  out  and  the  mother  liquor  is  treated  for  its 
alumina.  This  method  is  too  costly  when  compared  with  more 
recent  processes  to  be  used  at  present. 

According  to  Schuch*  very  finely-powdered  cryolite  is  dis- 
solved by  a  large  excess  of  hot  dilute  soda  solution,  but  is 
thrown  down  unaltered  when  carbonic  acid  gas  is  passed  through 
the  solution.  An  excess  of  concentrated  soda  liquor  converts  the 
mineral  into  sodium  aluminate  and  sodium  fluoride,  the  former 
being  soluble  but  the  latter  almost  insoluble  in  the  soda  solution. 

II. 

THE  PREPARATION  OF  ALUMINIUM  CHLORIDE  AND 
ALUMINIUM-SODIUM  CHLORIDE. 

Anhydrous  aluminium  chloride  cannot  be  made  by  evaporating 
the  solution  of  alumina  in  hydrochloric  acid,  for,  as  we  have 
seen,  decomposition  of  the  salt  sets  in,  hydrochloric  acid  is  evolved 
and  alumina  remains.  The  same  phenomena  occur  on  evaporat- 
ing a  solution  of  the  double  chloride.  These  anhydrous  chlorides 
are  prepared  by  a  method  discovered  by  Oerstedt,  applicable  to 
producing  a  number  of  similar  metallic  chlorides,  which  consists 
in  passing  a  current  of  dry  chlorine  gas  over  an  ignited  mixture 
of  alumina  and  carbon. 

Wohlerf  proceeded  as  follows  in  preparing  the  aluminium 
chloride  which  was  used  in  his  early  experiments:  "Alumina  is 
mixed  writh  charcoal  powder  and  made  plastic  with  oil.  Cylin- 
ders of  about  5  millimetres  diameter  are  made  of  this  paste, 
placed  in  a  crucible  with  charcoal  powder  and  heated  until  no 
more  combustible  gases  distil.  After  cooling  the  crucible  the 

; 

*  Poly  tech  ni  sch  es  Journal,  166,  p.  443. 
f  Pogg.  Aim.,  11,  p.  146. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS. 


123 


cylinders  are  taken  out,  and  a  porcelain  or  glass  tube  open  at 
both  ends  filled  with  them.  This  is  then  placed  in  a  combustion 
furnace,  connected  at  one  end  with  a  chlorine  generator,  and  at 
the  other  with  a  tubular  extension  from  the  further  end  of  which 
the  gases  escape,  either  into  the  air  or  into  a  flask  filled  with  milk 
of  lime.  When  the  whole  apparatus  is  ready,  and  filled  with 
well-dried  chlorine  gas,  the  tube  is  heated  to  glowing,  when  alu- 
minium chloride  is  formed  and  condenses  in  the  extension  of  the 
tube/7 

Deville  paid  great  attention  to  the  production  and  purification 
of  aluminium  chloride;  the  following  is  his  account  of  the  pro- 
cesses used  at  Javel : — 

Manufacture  on  a  small  scale. — "  I  took  5  kilos  of  alumina  and 
mixed  it  with  2  kilos  of  carbon  and  a  little  oil ;  the  paste  was 
made  into  balls  and  ignited  at  a  bright-red  heat.  The  compact, 
coke-like  mass  resulting  was  broken  in  pieces  and  put,  with  its 
powder,  into  a  stoneware  retort,  C  (Fig.  5),  having  a  capacity  of 


Fig.  5. 


about  10  litres,  and  terminating  in  a  neck,  D.  This  retort  was 
put  in  a  furnace  and  heated  to  redness,  while  a  current  of  dry 
chlorine  gas  passed  in  by  the  tube  A.  During  the  first  few 
moments  considerable  quantities  of  water  vapor  escape  from  the 
neck.  When  aluminium  chloride  distils,  as  is  shown  by  dense, 
white  fumes,  a  porcelain  or  stoneware  funnel,  E,  is  adjusted  to  the 
neck  D,  and  kept  in  place  by  filling  the  joint  with  fine  asbestos 
and  then  luting  it  over  with  a  little  potter's  clay  mixed  with  hair. 


1 24  ALUMINIUM. 

Against  this  funnel  fits  a  globular  vessel,  F,  the  joint  being  made 
tight  in  a  similar  way.  This  apparatus  condenses  and  holds  all 
the  chloride  distilled.  However  fast  the  chlorine  may  pass  into 
the  retort,  it  is  so  well  absorbed  during  three-fourths  of  the  opera- 
tion that  not  a  trace  is  mixed  with  the  carbonic  oxide  escaping. 
However,  the  gas  always  fumes  a  little  because  of  a  small  quantity 
of  silicon  chloride  being  formed  by  the  chlorine  and  carbon  attack- 
ing the  sides  of  the  retort,  or  from  chloride  of  sulphur  or  a  little 
chloroxycarbonic  acid.  When  the  globe  F  is  filled  it  is  taken 
away  to  extract  the  coherent,  crystalline  aluminium  chloride  it 
contains,  and  is  replaced  immediately  by  another.  During  one 
operation  three  jars  were  thus  filled,  and  altogether  a  little  over 
10  kilos  of  chloride  obtained.  In  the  retort  there  remained 
almost  a  kilo  of  coke  mixed  with  alumina  in  the  proportion  of 
two  of  carbon  to  one  of  alumina,  making  330  grammes  of  the 
latter  remaining  unattacked  out  of  5  kilos.  This  coke  contains 
also  some  double  chloride  of  alumina  and  potassium  and  a  little 
calcium  chloride,  which  render  it  deliquescent.  This  residue  was 
washed,  mixed  with  a  fresh  quantity  of  alumina,  and  employed  in 
a  new  operation." 

Manufacture  on  a  large  scale. — "  In  applying  this  process  on  a 
large  scale,  the  oil  and  carbon  were  replaced  by  tar,  the  alembic 
by  a  gas-retort  and  the  glass  receiver  by  a  small  brick  chamber 
lined  with  glazed  tiles.  The  alumina  was  obtained  by  calcining 
ammonia  alum  in  iron  pots ;  the  residue  obtained  by  one  calcina- 
tion at  a  bright-red  heat  was  mixed  with  pitch,  to  which  a  little 
charcoal  dust  was  added.  The  paste  was  well  mixed,  introduced 
into  iron  pots,  covered  carefully  and  heated  until  all  vapors  of 
tar  ceased  burning.  The  aluminous  carbon  is  used  while  it  is  still 
hot,  if  possible,  as  it  is  quite  hygroscopic.  (This  aluminous  car- 
bon conducts  electricity  wonderfully  well ;  it  is  the  best  electrode 
to  use  in  inaking  aluminium  by  the  battery,  since  its  alumina 
regenerates  the  bath.)  The  residue  is  hard,  porous,  and  cracked, 
and  contains  sulphur  from  the  sulphuric  acid  of  the  alum,  a  little 
iron,  phosphoric  acid  in  small  quantity,  a  perceptible  proportion 
of  lime,  and  finally  potash,  which  is  always  present  in  alums 
made  from  clay.  The  chlorine  gas  used  was  conducted  by  lead 
pipes  and  passed  over  calcium  chloride  before  being  used.  The 


PREPARATION   OF   ALUMINIUM   COMPOUNDS. 


125 


retort  used  was  of  about  300  litres  capacity,  and  was  placed  ver- 
tically in  a  sort  of  chimney,  C  (Fig.  6),  the  flame  circulating  all 
around  it.  In  the  bottom  was  a  square  opening,  x,  about  20 
centimetres  square,  which  could  be  closed  by  a  tile  kept  in  place 

Fig.  6. 


by  a  screw,  V.  A  porcelain  tube  pierced  the  sides  of  the  furnace 
and  entered  the  retort  at  0  ;  it  was  protected  from  the  flame  by  a 
fire-clay  cylinder  inclosing  it.  At  the  top,  the  retort  was  closed 
by  a  tile,  Z,  of  refractory  brick,  in  the  centre  of  which  was  made 
a  square  opening,  W,  of  10  to  12  centimetres  side.  Finally,  an 
opening,  Xy  placed  30  centimetres  below  the  plate  Z,  gave  issue 
to  the  vapors  distilled,  conducting  them  into  the  chamber  L. 
This  condension  chamber  was  about  1  metre  cube ;  it  had  one 
wall  of  bricks  in  common  with  the  furnace,  thus  keeping  it  rather 
hot.  The  other  walls  should  be  thin  and  set  with  close  joints 
and  very  little  mortar.  The  cover,  M,  was  movable;  it  and  the 
sides  of  the  chamber  were  of  glazed  tiles.  An  opening  20-30 
centimetres  square  in  the  lower  part  of  the  chamber  communicated 
with  flues  lined  with  lead,  for  a  little  chloride  was  drawn  into 
them.  The  uncondensed  gas  passed  to  a  chimney. 

"  To  work  such  an  apparatus  it  is  necessary,  first  of  all,  to  dry 


126  ALUMINIUM. 

it  with  the  greatest  care  in  all  its  parts,  especially  the  condensa- 
tion chamber.  The  retort  is  slowly  heated  and  is  left  open  at  Z 
until  it  is  judged  quite  dry,  and  is  then  filled  with  red-hot,  freshly 
calcined  mixture  of  carbon  and  alumina.  The  top  cover  is  then 
replaced  and  the  fire  urged  until  the  retort  is  at  a  dark-red  heat 
all  over.  Finally,  chlorine  is  passed  in,  but  the  opening  at  Wis 
kept  open ;  the  gas  is  allowed  to  pass  into  the  condensation 
chamber  only  when  fumes  of  aluminium  chloride  appear  very 
abundantly  at  W.  When  the  operation  proceeds  right,  almost 
all  the  aluminium  chloride  is  found  attached  in  a  dense,  solid 
mass  to  the  cover  M.  I  have  taken  out  at  one  time  a  plate  weigh- 
ing almost  50  kilogrammes,  which  was  less  than  10  centimetres 
thick  ;  it  was  made  up  of  a  large  number  of  sulphur-yellow  crys- 
tals penetrating  each  other  and  looking  like  stalactites  and  long 
soda  crystals.  When  it  is  judged  that  the  material  in  the  retort 
is  almost  exhausted,  the  hole  x  is  opened,  the  residue  scraped  out, 
and  fresh  mixture  put  in.  During  the  operation  there  should  be 
no  white  vapors  coming  from  the  condensation  chamber,  but  the 
odor  of  the  gas  will  always  be  sharp  because  of  the  silicon 
chloride  present,  formed  unavoidably  by  the  chlorine  attacking 
the  retort.  A  gas  retort,  handled  well,  should  last  continuously 
two  or  three  months,  or  even  more.  The  furnace  should  be  con- 
structed so  as  to  permit  its  easy  replacement  without  much 
expense.  When  in  use,  the  retort  is  closely  watched  through  spy- 
holes in  the  wall,  and  any  cracks  which  may  appear  promptly 
plastered  up,  if  not  large,  with  a  mixture  of  fine  asbestos  and 
soda  glass." 

Purification  of  aluminium  chloride. — "  It  often  happens  that 
the  chloride  obtained  is  not  pure,  either  from  the  nature  of  the 
apparatus  employed,  or  from  neglect  of  the  many  precautions 
which  should  be  taken.  In  this  case,  to  purify  it,  it  is  heated  in 
an  earthen  or  cast-iron  vessel  with  fine  iron  turnings.  When  the 
hydrochloric  acid,  hydrogen  and  permanent  gases  are  driven  from 
the  apparatus,  it  is  closed  and  heated  hotter,  which  produces  a 
light  pressure  under  which  influence  the  aluminium  chloride  melts 
and  enters  into  direct  contact  with  the  iron.  The  ferric  chloride, 
which  is  as  volatile  as  aluminium  chloride,  is  transformed  into 
ferrous  chloride,  which  is  much  less  volatile,  and  the  aluminium 


PREPARATION    OF   ALUMINIUM   COMPOUNDS.  127 

chloride  can  be  obtained  pure  by  being  volatilized  away  or  dis- 
tilled in  an  atmosphere  of  hydrogen." 

When  the  processes  just  described  were  put  in  use  at  the  chemi- 
cal works  at  La  Glaeiere,  great  care  had  to  be  taken  to  avoid 
letting  vapors  and  acid  gases  escape  into  the  air,  since  the  works 
were  surrounded  by  dwellings.  To  avoid  these  inconveniences, 
the  vapor  of  aluminium  chloride  was  made  to  enter  a  heated  space 
in  which  was  sodium  chloride,  in  order  to  produce  the  less  vola- 
tile double  chloride  ;  but  the  apparatus  choked  up  so  persistently 
that  the  attempt  was  given  up.  It  then  occurred  to  Deville  to  put 
sodium  chloride  into  the  mixture  itself  in  the  retort.  The  same 
apparatus  was  used  as  before,  except  that  the  large  gas-retort  had 
to  be  replaced  by  a  smaller  earthen  one  which  could  be  heated 
much  hotter,  the  grate  being  carried  half  way  up  the  retort.* 
The  condensation  chamber  had  to  be  replaced  by  a  small  earthen 
vessel.  The  double  chloride  produced  is  fusible  at  about  200°, 
and  is  quite  colorless  when  pure,  but  colored  yellow  by  iron.  It 
is,  moreover,  very  little  altered  in  dry  air  when  in  compact  masses 
and  can  be  easily  handled.  When  the  double  chloride  is  obtained 
quite  pure,  it  gives  up  its  aluminium  completely  when  reduced 
by  sodium. 

The  following  description  by  M.  Margottetf  will  show  the  form 
of  apparatus  used  in  1882  by  the  French  company  carrying  on 
the  Deville  process  at  Salindres  : — 

The  double  chloride  may  be  obtained  in  the  same  manner  as 
the  simple  chloride ;  it  is  sufficient  to  put  some  common  salt, 
NaCl,  into  a  mixture  of  alumina  and  carbon,  and,  on  heating  this 
mixture  strongly,  there  is  formed  by  the  action  of  the  chlorine, 
aluminium-sodium  chloride,  which  distils  at  a  red  heat  and  con- 
denses in  a  crystalline  mass  at  about  200°.  The  hydrated  alu- 
mina obtained  in  the  preceding  operation  is  mixed  with  salt  and 
finely  pulverized  charcoal,  in  proper  proportions,  the  whole  is 
sifted,  and  a  mixture  produced  as  homogeneous  as  possible  ;  then 
it  is  agglomerated  with  water  and  made  into  balls  the  size  of  the 

*  It  was  when  first  using  this  process  that  Deville  borrowed  some  zinc  re- 
torts from  the  Vielle  Montagne  works,  and  since  they  contained  a  little  zinc 
in  their  composition  the  aluminium  made  for  a  while  was  quite  zinciferrous. 

f  Fremy's  Ency.  Chimique. 


128 


ALUMINIUM. 


fist.  These  balls  are  first  dried  in  a  drying  stove,  at  about  150°, 
then  calcined  at  redness  in  retorts,  where  the  double  chloride 
should  commence  to  be  produced  just  as  the  balls  are  completely 
dried.  These  retorts  are  vertical  cylinders  of  refractory  earth, 
each  one  is  furnished  with  a  tube  in  its  lower  part  for  the  intro- 
duction of  chlorine,  and  with  another  towards  its  upper  end  for 
the  exit  of  the  vapor  of  double  chloride.  (See  Fig.  7.)  A  lid 


Fig.  7. 


carefully  luted  during  the  operation  with  a  mixture  of  fine  clay 
and  horse-dung  serves  for  the  charging  and  discharging  of  the 
retort.  The  double  chloride  is  condensed  in  earthen  pots  like 
flower  pots,  made  of  ordinary  clay,  and  closed  by  a  well-luted 
cover,  into  which  passes  a  pipe  of  clay  to  conduct  the  gas  result- 
ing from  the  operation  into  flues  connected  with  the  main  chimney. 
Each  retort  is  heated  by  a  fire,  the  flame  of  which  circulates  all 
round  it,  and  permits  keeping  it  at  a  bright  red  heat.  An  operation 
is  conducted  as  follows  :  The  retort  is  filled  with  stove  dried  balls, 
the  lid  is  carefully  luted,  and  the  retort  is  heated  gently  till  all 
the  moisture  is  driven  off.  This  complete  desiccation  is  of  great 
importance,  and  requires  much  time.  Then  chlorine,  furnished 
by  a  battery  of  three  generating  vessels,  is  passed  in.  During 
the  first  hours,  the  gas  is  totally  absorbed  by  the  balls;  the 
double  chloride  distils  regularly  for  about  three  hours,  and  runs 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  129 

into  the  earthen  pots  where  it  solidifies.  Toward  the  end,  the 
distillation  is  more  difficult  and  less  regular,  and  the  chlorine  is 
then  only  incompletely  absorbed.  After  each  operation  there  re- 
mains a  little  residue  in  the  retort,  which  accumulates  and  is  re- 
moved every  two  days,  when  two  operations  are  made  per  day. 
One  operation  lasts  at  least  twelve  hours,  and  a  retort  lasts  some- 
times a  month.  The  double  chloride  is  kept  in  the  pots  in  which  it 
was  condensed  until  the  time  it  is  to  be  used  in  the  next  operation  ; 
it  is  almost  chemically  pure,  save  traces  of  iron,  and  is  easy  to 
keep  and  handle. 

The  following  estimate  was  made  by  Wurtz,  in  1872,  showing 
the  cost  of  a  kilo  of  aluminium-sodium  chloride  as  made  by  the 
above  process : — 

Anhydrous  alumina  0.59  kilos  (5)  86  fr.  per  100  kilos  =  0  fr.  50.7  cent. 


Manganese  dioxide  3.74  "  "  14  " 
Hydrochloric  acid  15.72  "  "  3  " 
Coal  25.78  "  "  1.40 


Wages 
Expenses 


52.3 
47.1 


23.8 
38.0 


Total 2  "  48.0     " 

This  is  equal  to  about  22J  cents  per  pound.  An  average  of 
10  kilos  of  this  was  used  to  produce  one  kilo  of  aluminium,  which 
shows  a  yield  of  only  70  per  cent,  of  the  contained  aluminium, 
and  an  increased  cost  of  67  cents  on  every  pound  of  aluminium 
from  the  imperfection  of  reduction.  In  this  respect  there  certainly 
seems  large  room  for  improvement. 

The  largest  plant  ever  erected  for  the  manufacture  of  alu- 
minium-sodium chloride  is  that  of  the  Aluminium  Co.  Ltd.  at 
Oldbury  near  Birminghajn,  England.  The  plant  was  commenced 
in  the  latter  part  of  1887,  and  was  in  working  order  in  July,  1888. 
The  process  is  in  principle  identical  with  that  used  at  Salindres, 
but  the  whole  is  on  such  a  large  commercial  scale  that  the  appara- 
tus deserves  description. 

Twelve  large  regenerative  gas  furnaces  are  used,  in  each  of 
which  are  placed  five  horizontal  fire-clay  retorts  about  10  feet  in 
length,  into  which  the  mixture  is  placed.  These  furnaces  are  in 
two  rows,  of  six  each,  along  each  side  of  a  building  about  250 
feet  long,  leaving  a  clear  passage  down  the  centre  50  feet  wide- 
9 


130  ALUMINIUM. 

Above  this  central  passage  is  a  platform  swung  from  the  roof, 
which  carries  the  large  lead  mains  to  supply  chlorine  to  the  re- 
torts ;  opposite  each  retort  is  a  branch  pipe  controlled  by  a  valve. 
The  valves  are  designed  so  that  the  chlorine  must  pass  through  a 
certain  depth  of  (non-aqueous)  liquid,  thus  regulating  the  flow 
and  preventing  any  back  pressure  in  the  retort  from  forcing 
vapor  into  the  main.  The  opposite  or  back  ends  of  the  retorts 
are  fitted  with  pipes  which  convey  the  vapor  of  the  double  chlor- 
ide into  cast-iron  condensers  and  thence  into  brick  chests  or  boxes, 
the  outsides  or  ends  of  which  are  closed  by  wooden  doors  fitting 
tightly.  Convenient  openings  are  arranged  for  clearing  out  the 
passages,  which  may  become  choked  because  of  the  quickness 
with  which  the  double  chloride  condenses.  On  looking  down  the 
centre  of  the  building  it  presents  the  appearance  of  a  double  bank 
of  gas  retorts  for  making  ordinary  illuminating  gas,  except  that 
the  retorts  are  only  one  high. 

The  chlorine  plant  is  on  a  correspondingly  large  scale,  the 
usual  manganese-dioxide  method  being  employed  and  the  spent 
liquor  regenerated  by  Weldon's  process.  The  chlorine  gas  is 
stored  in  large  gasometers  from  which  it  is  supplied  to  the  retorts 
at  a  certain  pressure.  The  mixture  for  treatment  is  made  by 
mixing  hydrated  alumina  with  common  salt  and  carbon  in  the 
form  of  charcoal  powder  or  lamp-black.  This  being  well  mixed 
is  moistened  with  water,  thrown  into  a  pug-mill  from  which  it  is 
forced  out  as  solid  cylinders,  and  cut  into  about  3  inch  lengths  by 
a  workman.  The  lumps  are  then  piled  on  top  of  the  large  chlor- 
ide furnaces  to  dry.  In  a  few  hours  they  are  hard  enough  to 
allow  handling,  and  are  put  into  large  wagons  and  wheeled  to  the 
front  of  the  retorts. 

When  the  retorts  are  at  the  proper  temperature  for  charging, 
the  balls  are  thrown  in  until  the  retort  is  quite  full,  the  fronts  are 
then  put  up  and  luted  tightly  with  clay,  and  the  charge  left  alone 
for  about  four  hours,  during  which  the  water  of  the  hydrated 
alumina  is  completely  expelled,  the  rear  end  of  the  retort  being 
disconnected  from  the  condensing  chamber,  which  must  be  kept 
perfectly  dry,  and  connected  directly  with  the  chimney.  At  the 
end  of  this  time  the  chlorine  is  turned  on  and  the  retort  con- 
nected with  the  receiver.  At  first  the  chlorine  passed  in  is  all 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  131 

absorbed  by  the  charge  and  only  carbonic  oxide  escapes  into  the 
boxes,  where  it  is  ignited  and  burns,  thus  warming  them  up. 
After  a  certain  time  dense  fumes  are  evolved,  and  then  the  con- 
densers are  shut  tightly  and  the  uncondensed  gases  pass  into 
the  chimney.  The  chlorine  is  passed  in  for  72  hours  in  varying 
quantity,  the  boxes  at  the  rear  being  opened  from  time  to  time  by 
the  workmen  to  note  the  progress  of  the  distillation.  The  greater 
part  of  the  double  chloride  liquefies  and  trickles  down  to  the  floor 
of  the  chambers,  but  a  portion  sublimes  and  condenses  on  the 
walls  as  a  yellow  crystalline  powder.  These  chambers  are 
emptied  from  time  to  time  and  the  contents  packed  away  in  air- 
tight wooden  chests  that  it  may  keep  without  absorbing  moisture 
from  the  air.  At  the  end  of  the  distillation  the  chlorine  valves 
are  closed  and  the  condenser  boxes  cleaned  out ;  the  retorts  are 
also  opened  at  their  front  end  and  the  residue  raked  out.  This 
residue  consists  of  a  small  quantity  of  alumina,  charcoal  and  salt, 
and  is  remixed  in  certain  proportions  with  fresh  material  and  used 
over  again.  The  retorts  are  then  immediately  re-charged  and  the 
operations  repeated.  Each  set  of  five  retorts  produces  about 
1600  to  1800  Ibs.  in  one  operation,  or  say  3500  Ibs.  per  week. 
The  twelve  furnaces  are  therefore  capable  of  producing  easily 
1,500,000  Ibs.  of  double  chloride  per  annum.  Since  10  Ibs.  of 
this  salt  are  required  to  produce  1  Ib.  of  aluminium,  the  capacity 
of  the  works  is  thus  seen  to  be  150,000  Ibs.  or  over  of  metal  per 
year. 

This  last  remark  as  to  the  proportion  of  chloride  required  to 
form  the  metal  will  show  the  absolute  necessity  there  is  to  keep 
iron  from  contaminating  the  salt.  This  gets  in,  in  varying  pro- 
portions, from  the  iron  in  the  materials  used  and  in  the  fire-clay 
composing  the  retort,  and  exists  as  ferrous  and  ferric  chlorides. 
Exercising  the  utmost  care  as  to  the  purity  of  the  alumina  and 
charcoal  used,  and  after  having  the  retorts  made  of  a  special  fire- 
clay containing  a  very  small  percentage  of  iron,  it  was  found 
impossible  to  produce  a  chloride  on  a  large  scale  containing  less 
than  0.3  per  cent,  of  iron.  This  crude  chloride  is  highly  deliques- 
cent and  varies  in  color  from  light  yellow  to  dark  red — the  color 
depending  not  so  much  on  the  absolute  amount  of  iron  present  as 
on  the  proportion  of  iron  present  as  ferric  salt,  which  has  a  high 


132  ALUMINIUM. 

color.  Since  practically  all  the  iron  present  in  the  salt  passes 
into  the  aluminium,  it  is  seen  that  the  latter  would  contain  3  per 
cent,  or  more  of  iron.  For  some  time  the  only  way  to  obviate 
this  difficulty  was  to  resort  to  purifying  the  aluminium,  by  which 
the  content  of  iron  was  finally  reduced  to  2  per  cent.  Mr. 
Castner  has  since  perfected  a  process  for  purifying  the  double 
chloride  by  which  only  0.01  per  cent,  of  iron  is  left  in  it.  The 
principle  employed  in  doing  this  is  described  in  the  patent  claims* 
to  be  the  reduction  of  the  iron  salts  to  metallic  iron  by  melting 
the  chloride  (single  or  double)  with  a  quantity  of  metallic  alumin- 
ium or  sodium  sufficient  for  this  purpose.  The  purified  chloride 
is  quite  white  and  far  less  deliquescent  than  the  crude  salt,  which 
seems  to  indicate  that  the  iron  chlorides  have  a  large  share  in  ren- 
dering the  crude  salt  so  deliquescent.  The  purified  chloride  is 
preserved  by  melting  and  running  into  tight  iron  drums. 

The  success  of  the  manufacture  of  the  double  chloride  is  said 
to  depend  on  the  proportions  of  the  mixture,  the  temperature  of 
the  furnace,  the  quantity  of  chlorine  introduced  and  the  details 
of  construction  of  the  retorts ;  but  very  little  information  on  these 
points  has  been  made  public.  The  following  figures  may  give 
some  idea  of  the  quantities  of  materials  used :  The  production 
of  100  Ibs.  of  double  chloride  is  said  to  require — 

Common  salt 357  Ibs. 

Hydrated  alumina  .         .         .         .         .     491    " 

Chlorine  gas .     674   " 

Coal 1800   " 

The  salt  and  hydrated  alumina  are  therefore  mixed  in  about 
the  same  proportions  as  those  indicated  by  the  formula  which 
represents  the  reaction 

APO3 + 2NaCl  +  3C  +  6C1 = APCl6.2NaCl  +  3CO. 

for  if  we  assume  the  hydrated  alumina  used  to  contain  90  per 
cent,  of  that  compound,  the  491  Ibs.  of  it  used  would  correspond 
to  very  nearly  the  amount  of  salt  said  to  be  used.  As  to  the 
cost  of  this  double  chloride,  so  many  uncertain  elements  enter 
into  it  that  it  cannot  be  satisfactorily  estimated  from  the  data  at 

*  U.  S.  Patent,  No.  409668,  Aug.  27,  1889. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  133 

hand.  We  are  informed,  however,*  that  the  double  chloride  used 
represents  43  per  cent,  of  the  cost  of  aluminium  to  this  company. 
If  we  place  the  total  cost  at  8  shillings  per  Ib.  this  would  indicate 
a  trifle  over  4  pence  per  Ib.  as  the  cost  of  the  double  chloride. 
I  think  it  is  probably  not  over  3  pence. 

H.  A.  Gadsden,f  of  London,  has  patented  a  method  of  obtain- 
ing aluminium  in  which  the  aluminium  chloride  used  is  obtained 
by  a  method  similar  in  all  respects  to  the  process  as  described  by 
Deville  except  that  the  corundum  or  beauxite  used  is  mixed  with 
about  10  per  cent,  of  sodium  or  potassium  fluoride  and  a  small 
quantity  of  fluorspar.  After  this  has  been  mixed  and  calcined 
it  is  pulverized,  10  per  cent,  of  charcoal  dust  added,  made  into 
balls  and  heated  in  a  muffle  until  pasty.  Taken  out  of  the  muf- 
fle they  are  then  put  into  a  retort,  heated  highly,  and  chlorine  gas 
passed  over  them,  when  aluminium  chloride  distils. 

Count  R.  de  MontgelasJ  patents  a  process  for  producing  alu- 
minium chloride  and  the  double  chloride  with  sodium,  in  which 
the  only  difference  from  the  preceding  methods  is  that  molasses  is 
used  instead  of  pitch  for  moulding  the  mixture  into  balls,  the 
mixture  otherwise  containing  alumina,  charcoal,  and  sodium  chlor- 
ide, and  it  is  claimed  that  by  regulating  the  heat  at  which  chlorine 
is  passed  over  this  mixture,  previously  calcined,  aluminium  chlor- 
ide can  be  volatilized  while  aluminium-sodium  chloride  remains 
in  the  retort.  The  use  of  horizontal  retorts  is  recommended,  and 
these  certainly  possess  advantages  over  the  vertical  ones,  but  I  am 
unable  to  say  if  this  process  has  the  merit  of  being  the  pioneer  in 
this  direction. 

Prof.  Chas.  F.  Mabery,§  of  the  Case  School  of  Applied  Science, 
Cleveland,  patented  and  assigned  to  the  Cowles  Bros,  the  process 
of  making  aluminium  chloride,  consisting  in  passing  dry  chlorine 
or  hydrochloric  acid  gas  over  an  alloy  of  aluminium  and  some 
other  metal  kept  in  a  closed  vessel  at  a  temperature  sufficient  to 
volatilize  the  aluminium  chloride  formed,  which  is  caught  in  a 
condenser.  Or,  hydrochloric  acid  gas  is  passed  through  an  elec- 

*  Zeitschrift  des  Vereins  Deutscher  Ingenieure,  1889,  p.  301. 
f  German  Patent  (D.  R.  P.)  No.  27572  (1884). 
J  English  Patent,  Nos.  10011,  10012,  10013,  Aug.  4,  1886. 
§   U.  S.  Patent,  Oct.  26,  1886. 


134  ALUMINIUM. 

trically  heated  furnace  in  which  alumina  is  being  decomposed  by 
carbon,  a  condenser  being  attached  to  the  opposite  end  of  the 
furnace. 

Mr.  Paul  Curie*  states  that  aluminium  chloride  can  be  made 
by  passing  vapors  of  carbon  disulphide  and  hydrochloric  acid 
either  simultaneously  or  successively  over  ignited  alumina  or  clay. 
The  first  forms  aluminium  sulphide  which  the  latter  converts 
into  the  volatile  chloride,  which  distils. 

H.  W.  AVarrenf  recommends  the  following  process  as  of  gen- 
eral application  in  producing  anhydrous  metallic  chlorides : 
Petroleum  is  saturated  with  either  chlorine  or  hydrochloric  acid 
gas,  both  gases  being  soluble  in  it  to  a  large  extent,  particularly 
the  latter  gas.  This  operation  is  performed  at  a  low  temperature, 
as  more  of  the  gases  is  then  dissolved.  The  oxide  of  the  metal, 
alumina  for  instance,  is  put  into  large  earthenware  retorts  and 
raised  to  red  heat.  The  saturated  oil  is  then  boiled  and  its  vapor 
passed  into  the  retort.  On  contact  with  the  oxide  a  strong  reac- 
tion commences,  fumes  of  aluminium  chloride  are  at  once  evolved 
and  distil  into  a  condenser,  the  operation  being  continued  until 
no  more  white  fumes  appear.  Then  fresh  alumina  is  supplied, 
and  the  reaction  continues.  The  aluminium  chloride  may  be 
purified  from  any  oil  by  gentle  application  of  heat.  Mr.  War- 
ren also  used  naphthaline  chloride  with  advantage,  as  also  chloride 
of  carbon,  but  their  high  price  rendered  them  unable  to  compare 
with  petroleum  in  economy.  Aluminium  bromide  can  be  simi- 
larly prepared  by  substituting  bromine  for  chlorine. 

Camille  A.  Faure,  of  New  York,  the  well-known  inventor  of 
the  Faure  storage  battery,  has  patented^  a  process  for  producing 
aluminium  chloride  which  is  very  similar  to  the  above  method. 
The  manipulation  is  described  as  follows :  An  oxygenated  ore  of 
aluminium  is  brought  to  about  a  red  heat  by  bringing  it,  in  a 
furnace,  into  direct  contact  with  the  flame.  When  at  proper  heat 
the  flame  is  cut  off  and  a  gas  containing  carbon  and  chlorine  in- 
troduced. A  mixture  of  petroleum  vapor  or  a  similar  hydro- 

*  Chemical  News,  1873,  p.  307. 

f  Chemical  News,  April  29,  1887. 

t  U.  S.  Patent,  No.  385345,  July  3,  1888. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  135 

carbon   with   hydrochloric   acid    gas    is   preferred.      Vaporized 
chloride  of  aluminium  immediately  passes  off  into  a  condenser. 

In  a  paper  written  by  Mr.  Faure,  and  read  before  the  French 
Academy  of  Sciences  by  M.  Berthelot,*  it  was  stated  that  the 
aim  of  this  process  was  to  suppress  the  prominent  disadvantages 
of  the  older  methods :  viz.,  cost  and  wear  and  tear  of  retorts, 
great  consumption  of  fuel,  slowness  of  the  operation,  large  amount 
of  labor,  and  cost  of  the  chlorine.  For  this  purpose  the  chlorine 
is  replaced  by  hydrochloric  acid  gas  and  the  carbon  by  a  hydro- 
carbon, Since  all  pure  hydrocarbons  are  decomposed  at  a  red  heat 
with  deposition  of  carbon  the  process  would  appear  impracticable, 
but  a  proper  mixture  of  hydrochloric  acid  gas  and  naphtha- 
line vapor  is  said  not  to  decompose  by  the  highest  temperature 
alone,  a  new  compound  being  formed,  a  sort  of  naphthaline  chlo- 
ride, which  is  exceedingly  corrosive  and  powerful  enough  to 
attack  any  oxide  and  convert  it  into  chloride.  To  carry  out  the 
process  a  gas  furnace  with  large  bed  is  used.  On  this  is  spread  a 
layer  of  small  pieces  of  beauxite  about  two  feet  deep.  The  flame 
comes  in  over  the  ore,  passes  downward  through  it  and  through 
numerous  holes  arranged  in  the  hearth,  and  thence  to  a  chimney. 
In  this  way  the  heat  of  the  gases  is  well  utilized,  while  the 
layer  of  beauxite  is  heated  to  whiteness  on  top  and  to  low-red  at 
the  bottom.  The  flames  are  then  turned  off  and  the  mixture  of 
naphthaline  and  hydrochloric  acid  vapors  passed  upward  through 
the  bed,  and  by  their  reaction  producing  aluminium  chloride, 
which  is  diverted  by  suitable  flues  into  a  condenser.  It  is  claimed 
that  by  careful  fractional  condensation  the  chlorides  of  silicon, 
iron,  calcium,  etc.,  formed  from  impurities  in  the  beauxite,  can  be 
easily  separated,  that  of  silicon  being  more  volatile  and  those  of 
iron  and  calcium  less  volatile  than  aluminium  chloride.  As  naph- 
thaline is  a  bye  product  from  gas-works,  it  is  claimed  that  it  can 
be  bought  for  1|  cents  per  lb.,  and  that  only  J  of  a  Ib.  is  used 
per  lb.  of  aluminium  chloride  produced.  It  is  also  claimed  that 
one  furnace,  with  two  men  to  work  it,  will  produce  4000  Ibs.  of 
chloride  a  day.  The  estimated  cost  of  the  chloride  is  about  1 J 
cents  per  pound,  of  which  17  per  cent,  is  for  beauxite,  47  per 

*  July  30,  1888. 


136  ALUMINIUM. 

cent,  for  hydrochloric  acid,  27  per  cent,  for  naphthaline,  and  9  per 
cent,  for  labor.  Mr.  Faure  has  been  experimenting  in  the  vicinity 
of  New  York  during  the  last  few  months,  and  is  sanguine  of 
having  the  process  at  work  commercially  in  1890.  (See  further, 
Chap.  XL) 

In  all  the  processes  for  producing  aluminium  chloride  so  far 
considered  the  use  of  common  clay  was  not  recommended,  since 
silicon  chloride  is  formed  as  well  as  aluminium  chloride.  The 
only  method  proposed  for  using  clay  for  this  purpose  is  that  of 
M.  Dullo,  nearly  twenty  years  ago,  and  which  cannot  have  been 
very  successful,  since  it  has  not  been  heard  of  in  operation.  We 
will  repeat  his  remarks,  however,  for  there  is  still  a  large  field 
open  in  the  utilization  of  clay  for  the  manufacture  of  aluminium, 
and  since  the  metal  is  becoming  so  cheap  the  manufacturers  are 
not  above  looking  for  and  utilizing  the  cheapest  raw  material 
available. 

*  "  Aluminium  chloride  may  be  obtained  easily  by  direct  treat- 
ment of  clay.  For  this  purpose  a  good  clay,  free  from  iron  and 
sand,  is  mixed  with  enough  water  to  make  a  thick  pulp,  to  which 
are  added  sodium  chloride  and  pulverized  carbon.  For  every  100 
parts  of  dry  clay  there  are  taken  120  parts  of  salt  and  30  of  car- 
bon. The  mixture  is  dried  and  broken  up  into  small  fragments, 
which  are  then  introduced  into  a  red-hot  retort  traversed  by  a 
current  of  chlorine.  Carbonic  oxide  is  disengaged,  while  at  the 
same  time  aluminium  chloride  and  a  little  silicon  chloride  are 
formed.  It  is  not  necessary  that  the  chlorine  should  be  absolutely 
dry,  it  may  be  employed  just  as  it  comes  from  the  generator.  The 
gas  is  absorbed  very  rapidly,  because  between  the  aluminium  and 
silicon  there  are  reciprocal  actions  under  the  influence  of  which 
the  chemical  actions  are  more  prompt  and  energetic.  The  alu- 
minium having  for  chlorine  a  greater  affinity  than  silicon  has,  alu- 
minium chloride  is  first  formed,  and  it  is  only  when  all  the  alu- 
minium is  thus  transformed  that  any  silicon  chloride  is  formed. 
When  the  latter  begins  to  form  the  operation  is  stopped,  the  in- 
candescent mixture  is  taken  out  of  the  retort  and  treated  with 
water.  The  solution  is  evaporated  to  dryness  to  separate  out  a 

*  Bull,  de  la  Soc.  Chem.  1860,  vol.  v.  p.  472. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  137 

small  quantity  of  silica  which  is  in  it,  the  residue  is  taken  up 
with  water,  and  aluminium-sodium  double  chloride  remains  when 
the  filtered  solution  is  evaporated  to  dry  ness." 

"We  must  say  of  M.  Dullo's  suggestions  that  it  is  the  general 
experience  that  the  more  volatile  silicon  chloride  is  formed  first ; 
it  is  also  very  improbable  that  a  solution  of  aluminium-sodium 
chloride  can  be  evaporated  without  decomposition. 

III. 

THE  PREPARATION  OF  ALUMINIUM  FLUORIDE  AND 
ALUMINIUM-SODIUM  FLUORIDE.     (CRYOLITE.) 

Natural  cryolite  is  too  impure  for  use  in  many  operations  which 
aim  to  produce  very  pure  aluminium.  Schuh  has  proposed  boil- 
ing the  mineral  in  solution  of  soda.  Under  certain  conditions 
sodium  aluminate  is  formed  (see  p.  1 22),  but  if  the  solution  of  soda 
is  dilute  the  liquor  remains  clear  after  taking  up  the  cryolite,  and 
on  passing  a  current  of  carbonic  acid  gas  through  it  aluminium- 
sodium  fluoride  is  precipitated.  In  this  way  the  pure  double 
fluoride  can  be  separated  from  impure  cryolite. 

Berzelius  recommended  preparing  artificial  cryolite  by  decom- 
posing aluminium  hydrate  by  a  solution  of  sodium  fluoride  and 
hydrofluoric  acid,  the  hydrate  being  added  to  the  liquid  until  its 
acidity  was  just  neutralized  : — 

A12O3.3H2O  -f  6NaF  +  6HF  =  Al2F6.6NaF  -f  6H2O. 

If  a  solution  of  sodium  fluoride  alone  is  used,  half  the  alu- 
minium and  half  the  sodium  will  remain  in  the  solution  as  sod- 
ium aluminate : — 

2A12O3.3H2O  +  12NaF  =  Al2F6.6NaF  +  Al2O3.3Na2O  +  3H2O. 

Deville  states  that  on  adding  sodium  chloride  to  a  solution  ob- 
tained by  dissolving  alumina  in  an  excess  of  hydrofluoric  acid,  a 
precipitate  of  cryolite  is  obtained.  Since  cryolite  is  hardly  at- 
tacked at  all  by  hydrochloric  acid,  it  is  probable  that  the  reaction 
occurring  is 

A12F6  +  6HF  +  6NaCl  =  Al2F6.6NaF  +  6HC1. 


138  ALUMINIUM. 

The  process  which  Deville  recommended  as  best,  however,  is 
the  treatment  of  a  mixture  of  calcined  alumina  and  carbonate  of 
soda,  mixed  in  the  proportions  in  which  their  bases  exist  in  cryo- 
lite, by  an  excess  of  pure  hydrofluoric  acid  :  — 

A12O3  +  3Na2CO3  +  12HF  =  Al2F6.6NaF  +  SCO2  +  6H2O. 

100  parts  of  pure  alumina  requiring  310  parts  of  sodium  carbonate 
and  245  of  anhydrous  hydrofluoric  acid,  there  being  410  parts  of 
cryolite  formed.  On  drying  the  mass  and  melting  it  there  results 
a  limpid,  homogeneous  bath  having  all  the  characteristics  of  cryo- 
lite, being  reduced  by  sodium  or  by  an  electric  current,  which 
would  not  result  from  a  mere  mixture  of  alumina  and  sodium 
fluoride  melted  together. 

Deville  also  states  that  when  anhydrous  aluminium  chloride 
is  heated  with  sodium  fluoride  in  excess,  a  molten  bath  results  of 
great  fluidity,  and  on  cooling  and  dissolving  away  the  excess  of 
sodium  fluoride  by  repeated  washings  the  residue  is  similar  to 
cryolite,  while  the  solution  contains  no  trace  of  any  soluble  alu- 
minium salt  :  — 

A12C16  +  12NaF  =  Al2F6.6NaF  +  6NaCl. 

It  is  evident,  however,  that  the  above  reaction  would  be  the  re- 
verse of  a  profitable  one,  and  is  therefore  not  of  economical  utility. 

Pieper*  patents  a  very  similar  reaction  but  operates  in  the  wet 
way.  A  solution  of  aluminium  chloride  is  decomposed  by  adding 
to  it  a  suitable  quantity  of  sodium  fluoride  in  solution.  Sodium 
chloride  is  formed  and  cryolite  precipitated,  as  in  the  last  reaction 
given.  By  adding  different  proportions  of  sodium  fluoride  solu- 
tion precipitates  of  double  salts  are  obtained  containing  varying 
proportions  of  the  two  fluorides.  The  use  of  aluminium  chloride 
in  solution  would  dispense  with  the  objection  made  to  Deville's 
analogous  method,  and  this  process  would  very  probably  produce 
cryolite  quite  cheaply. 

Brunerf  produced  aluminium  fluoride  by  passing  hydrofluoric 
acid  gas  in  the  required  quantity  over  alumina  heated  red  hot  in 
a  platinum  crucible  :  — 

APO3  +  6HF  =  A12F6  +  3H2O. 


German  Patent  (D.  R.  P.),  No.  35212.        f  p°gg-  Annalen,  98,  p.  488. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  139 

Deville*  states  that  it  can  be  made  by  melting  together  equiva- 
lent quantities  of  cryolite  and  aluminium  sulphate  : — 

APF6.6NaF  +  AP(SO4)3.tfH2O  =  2A12F6  +  3Na2SO4  +  o:H2O. 

On  washing  the  fusion,  sodium  sulphate  goes  into  solution.  It 
is  also  stated  that  hydrochloric  acid  gas  acting  on  a  mixture  of 
fluorspar  arid  alumina  at  a  high  temperature  will  produce  alumin- 
ium fluoride : — 

APO3  +  3CaF2  +  6HC1  =  APF6  +  3CaCP  +  3H2O. 

The  calcium  chloride  would  be  partly  volatilized  and  the  re- 
mainder washed  out  of  the  fusion. 

Hautefeuillef  obtained  crystallized  aluminium  fluoride  by  pass- 
ing hydrofluoric  acid  gas  and  steam  together  over  red-hot  alumina. 

Ludwig  Grabau,  of  Hanover,  bases  his  process  of  producing 
aluminium  on  the  reduction  of  aluminium  fluoride  (see  Chap.  X.), 
which  is  prepared  on  a  commercial  scale  by  the  following  inge- 
nious methods  : — 

JThe  process  is  based  on  the  conversion  of  aluminium  sulphate 
into  fluoride  by  reaction  with  cryolite,  the  fluoride  being  after- 
wards reduced  by  sodium  in  such  manner  that  a  double  fluoride 
of  sodium  and  aluminium'  results  which  is  used  over  again,  thus 
forming  a  continuous  process.  The  purest  obtainable  cryolite  is 
used  to  start  the  process,  after  which  no  more  is  needed,  the  ma- 
terial supplying  the  aluminium  being  its  sulphate,  which  can  be 
obtained  cheaply  in  large  quantities  and  almost  perfectly  pure. 
The  process  is  outlined  by  the  reactions — 

APF6.6NaF  +  AP(SO4)3=  2APF6  +  3Na2SO4 
2  APF6  4-  6Na=  2  Al  +  Al2F6.61STaF. 

It  is  thus  seen  that  theoretically  the  cryolite  would  be  exactly  re- 
produced, but  the  losses  and  incomplete  reactions  unavoidable  in 
practice  would  cause  less  to  be  obtained  and  necessitate  the  con- 
tinual addition  of  fresh  cryolite;  since,  however,  it  is  not  desired 
to  base  the  process  on  the  continual  use  of  cryolite,  because  of  the 

*  Ann.  de  Chim.  et  de  Phys.  [3],  61,  p.  333  ;  [3],  49,  p.  79 

f  Idem,  [4 J,  4,  p.  153. 

t  German  Patent  (D.  R.  P.)  No.  48535,  March  8,  1889. 


140  ALUMINIUM. 

impurities  in  that  mineral,  an  indirect  process  is  used  consisting 
of  two  reactions,  in  place  of  the  first  given  above,  in  which 
theoretically  a  larger  quantity  of  cryolite  is  finally  obtained  than 
is  used  to  begin  with.  This  is  operated  by  introducing  fluorspar 
into  the  process,  the  base  of  which  goes  out  as  calcium  sulphate 
or  gypsum  and  so  supplies  the  fluorine  needed. 

In  practice,  a  solution  of  aluminium  sulphate  is  heated  with 
powdered  fluorspar  (obtained  as  pure  as  possible  and  further 
cleaned  by  treatment  with  dilute  hydrochloric  acid).  The  alu- 
minium sulphate  will  not  be  entirely  converted  into  fluoride,  as 
has  been  previously  observed  by  Friedel,  but  about  two-thirds 
of  the  sulphuric  acid  is  replaced  by  fluorine,  forming  a  fluor- 
sulphate  of  aluminium.  This  latter  compound  remains  in  solution, 
while  gypsum  and  undecomposed  fluorspar  remain  as  a  residue 
and  are  filtered  out. 

A12(SO4)3  +  2CaF2= A12F4(SO4)  +  2CaSO4. 

This  solution  is  concentrated  and  mixed  with  cryolite  in  such 
proportion  that  the  alkali  in  the  latter  is  just  equivalent  to  the 
sulphuric  acid  in  the  fluor-sulphate.  The  mass  is  dried  and 
ignited,  and  the  product  washed  and  dried. 

3A12F4(SO4)  +  Al2F6.6NaF= 4A12F6  +  3Na2SO4. 

On  reduction  with  sodium,  the  4  molecules  of  aluminium  fluoride, 
treated  with  sodium  as  by  the  reaction  given,  produce  2  molecules 
of  the  double  fluoride.  It  is  thus  seen  that  after  allowing  for 
reasonable  losses  in  the  process  there  is  much  more  cryolite  pro- 
duced than  is  used,  and  the  excess  can  be  very  profitably  sold  as 
pure  cryolite,  being  absolutely  free  from  iron  or  silica. 

IV. 

THE  PREPARATION  OF  ALUMINIUM  SULPHIDE. 

Until  the  researches  of  M.  Fremy,  no  other  method  of  pro- 
ducing aluminium  sulphide  was  known  save  by  acting  on  the 
metal  with  sulphur  at  a  very  high  heat.  Fremy  was  the  first 
to  open  up  a  different  method,  and  it  may  be  that  his  discoveries 
will  yet  be  the  basis  of  successful  industrial  processes.  In  order 


PREPARATION  OF   ALUMINIUM   COMPOUNDS.  141 

to  understand  just  how  much  he  discovered  we  here  give  all  that 
his  original  paper  contains  concerning  this  sulphide.* 

"  We  know  that  sulphur  has  no  action  on  silica  or  boric  oxide, 
magnesia,  or  alumina.  I  thought  that  it  might  be  possible  to 
replace  the  oxygen  by  sulphur  if  I  introduced  or  intervened  a 
second  affinity,  as  that  of  carbon  for  oxygen  These  decomposi- 
tions produced  by  two  affinities  are  very  frequent  in  chemistry ;  it 
is  thus  that  carbon  and  chlorine,  by  acting  simultaneously  on 
silica  or  alumina,  produce  silicon  or  aluminium  chloride,  while 
either  alone  could  not  decompose  it ;  a  similar  case  is  the  decom- 
position of  chromic  oxide  by  carbon  bisulphide,  producing  chrom- 
ium sesquisulphide.  Reflecting  on  these  relations,  I  thought 
that  carbon  bisulphide  ought  to  act  at  a  high  heat  on  silica, 
magnesia,  and  alumina,  producing  easily  their  sulphides.  Experi- 
ment has  confirmed  this  view.  I  have  been  able  to  obtain  in  this 
way  almost  all  the  sulphides  which  until  then  had  been  produced 
only  by  the  action  of  sulphur  on  the  metals. 

"  To  facilitate  the  reaction  and  to  protect  the  sulphide  from 
the  decomposing  action  of  the  alkalies  contained  in  the  porcelain 
tube  which  was  used,  I  found  it  sometimes  useful  to  mix  the 
oxides  with  carbon  and  to  form  the  mixture  into  bullets  resem- 
bling those  employed  in  the  preparation  of  aluminium  chloride. 
I  ordinarily  placed  the  bullets  in  little  carbon  boats,  and  heated 
the  tube  to  whiteness  in  the  current  of  vaporized  carbon  bisul- 
phide. The  presence  of  divided  carbon  does  not  appear  useful 
in  the  preparation  of  this  sulphide. 

"  The  aluminium  sulphide  formed  is  not  volatile ;  it  remains 
in  the  carbon  boats  and  presents  the  appearance  of  a  melted 
vitreous  mass.  On  contact  with  water  it  is  immediately  decom- 
posed. 

APS3  +  3H2O= APO3  +  3H2S. 

"  The  alumina  is  precipitated,  no  part  of  it  going  into  solution. 
This  precipitated  alumina  is  immediately  soluble  in  weak  acids. 
The  clear  solution,  evaporated  to  dryness,  gives  no  trace  of 
alumina.  It  is  on  this  phenomenon  that  I  base  the  method  of 
analysis. 

*  Ann.  de  Chem.  et  de  Phys.  [3]  xxxviii.  312. 


142  ALUMINIUM. 

u  Aluminium  sulphide  being  non-volatile,  it  is  always  mixed 
with  some  undecomposed  alumina.  It  is,  in  fact,  impossible  to 
entirely  transform  all  the  alumina  into  sulphide.  I  have  heated 
less  than  a  gramme  of  alumina  to  redness  five  or  six  hours  in 
carbon  bisulphide  vappr,  and  the  product  was  always  a  mixture 
of  alumina  and  aluminium  sulphide.  The  reason  is  that  the 
sulphide  being  non-volatile  and  fusible  coats  over  the  alumina 
and  prevents  its  further  decomposition.  The  alumina  thus  mixed 
with  the  sulphide,  and  which  has  been  exposed  to  a  red  heat  for 
a  long  time,  is  very  hard,  scratches  glass,  and  is  in  grains  which 
are  entirely  insoluble  in  acids.  By  reason  of  this  property  I 
have  been  able  to  analyze  the  product  exactly,  for  on  treating  the 
product  with  water  and  determining  on  the  one  hand  the  sulphu- 
retted hydrogen  evolved,  and  on  the  other  the  quantity  of  soluble 
alumina  resulting,  I  have  determined  the  two  elements  of  the 
compound.  One  gramme  of  my  product  contained  0.365  grrn. 
of  aluminium  sulphide,  or  36.5  per  cent.,  the  remainder  being 
undecomposed  alumina."  The  composition  of  this  sulphide  was — 

Aluminium   .....     0.137  grm.  =  37.5  per  cent. 
Sulphur 0.228     "     =  62.5  " 


0.365     "        100.0       " 

The  formula  APS3  requires — 

Aluminium .36.3  per  cent. 

Sulphur        , 63.7       " 

The  above  is  the  substance  of  Fremy's  investigations  and 
results.  Reichel*  next  published  an  account  of  further  experi- 
ments in  this  line.  He  found  that  by  melting  alumina  and  sul- 
phur together  no  reaction  ensued.  In  the  case  of  magnesia,  the 
sulphide  was  formed  if  carbon  was  mixed  with  the  magnesia  and 
sulphur,  but  this  change  did  not  alter  the  alumina.  Hydrogen 
gas  passed  over  a  mixture  of  alumina  and  sulphur  likewise  gave 
negative  results.  Sulphuretted  hydrogen  passed  over  ignited  alu- 
mina did  not  succeed.  By  filling  a  tube  with  pure  alumina,  pass- 
ing in  hydrogen  gas  and  the  vapor  of  carbon  bisulphide,  the  heat- 
ing being  continued  until  carbon  bisulphide  condensed  in  the 

*  Jahresb.  der  Chemie,  1867,  p.  155. 


PREPARATION   OF   ALUMINIUM   COMPOUNDS.  143 

outlet  tube,  and  then  hydrogen  being  passed  through  until  the 
tube  was  cold,  a  product  was  obtained  containing  aluminium  sul- 
phide and  undecomposed  alumina. 

In  1886,  I  made  a  series  of  experiments  on  the  production 
and  reduction  of  aluminium  sulphide.  Alumina,  either  alone  or 
mixed  with  carbon  or  with  carbon  and  sulphur,  was  put  in  porce- 
lain or  carbon  boats  into  a  hard  glass  or  porcelain  tube.  This 
was  then  heated  and  vapor  of  carbon  bisulphide  passed  over  it. 
The  product  was  analyzed  according  to  Fremy's  directions.  The 
proportion  of  aluminium  sulphide  obtained  in  the  product  varied 
from  13  to  40  per  cent.  The  best  result  was  obtained  at  the 
highest  heat — almost  whiteness.  The  presence  of  sulphur  or  car- 
bon, or  both  together,  mixed  with  the  alumina  did  not  promote 
to  any  degree  the  formation  of  a  richer  product.  The  conditions 
for  obtaining  the  best  results  seem  to  be  high  heat  and  fine  divis- 
ion of  the  alumina  to  facilitate  its  contact  with  the  carbon 
bisulphide  vapor.  The  product  was  light -yellow  when  not 
mixed  with  carbon,  easily  pulverized,  and  evolved  sulphuretted 
hydrogen  gas  energetically  when  dropped  into  water.  Since  car- 
bon bisulphide  can  now  be  manufactured  at  a  very  low  price,  say 
2  to  3  cents  per  lb.,  it  is  not  impossible  that  it  may  be  found  pro- 
fitable to  produce  aluminium  from  its  sulphide.  In  such  a  case, 
large  retorts  would  be  used,  a  stirring  apparatus  would  facilitate 
the  formation  of  a  richer  product,  and  the  unused  carbon  bisul- 
phide could  be  condensed  and  saved. 

M.  Comenge,*  of  Paris,  proposed  to  prepare  aluminium  sul- 
phide by  using  a  clay  retort  similar  to  those  used  in  gas-works, 
filling  it  one-half  its  length  with  charcoal  or  coke  and  the  other 
half  with  alumina.  The  retort  being  heated  to  redness,  sulphur 
is  introduced  at  the  coke  end,  when  in  contact  with  the  carbon  it 
forms  carbon  bisulphide,  which  acts  upon  the  alumina  at  the 
other  end,  producing  the  sulphide. 

Messrs.  Reillon,  Montague,  and  Bourgerelf  obtained  a  patent 
in  England  for  producing  aluminium,  in  which  aluminium  sul- 
phide is  obtained  by  mixing  powdered  alumina  with  40  per  cent. 

*  English  Patent,  1858,  No.  461. 

f  English  Patent,  No.  4756,  March  28,  1887. 


144  ALUMINIUM. 

of  its  weight  of  charcoal  or  lampblack  and  formed  into  a  paste 
with  a  sufficient  quantity  of  oil  or  tar.  This  is  then  calcined  in 
a  closed  vessel  and  an  aluminous  coke  obtained.  This  is  broken 
into  pieces,  put  into  a  retort,  and  treated  with  carbon  bisulphide 
vapor.  The  inventors  state  that  the  reaction  takes  place  accord- 
ing to  the  formula  2Al2O3-f-3C  +  3CS2=2Al2S3-f  6CO. 

Petitjean*  states  that  if  alumina  is  mixed  with  tar  or  turpen- 
tine and  ignited  in  a  carbon-lined  crucible,  and  the  coke  obtained 
mixed  intimately  with  sulphur  and  carbonate  of  soda  and  ignited 
a  long  time  at  bright  redness,  there  results  a  double  sulphide  of 
aluminium  and  sodium,  from  which  aluminium  can  be  easily 
extracted. 

It  has  been  statedf  that  if  aluminium  fluoride  is  heated  with 
calcium  sulphide,  aluminium  sulphide  results.  F.  LauterbornJ 
also  makes  the  same  claim  in  a  patent  twenty  years  later,  but  the 
possibility  of  this  reaction  taking  place  is  not  yet  beyond  ques- 
tion. 


CHAPTER  VII. 

THE   MANUFACTURE   OF   SODIUM. 

SOME  years  ago,  in  order  to  treat  fully  of  the  metallurgy  of 
aluminium,  it  would  have  been  as  necessary  to  accompany  it 
with  all  the  details  of  the  manufacture  of  sodium  as  to  give  the 
details  of  the  reduction  of  the  aluminium,  because  the  manufac- 
ture of  the  former  was  carried  on  solely  in  connection  with  that 
of  the  latter.  But  now  sodium  has  come  out  of  the  list  of 
chemical  curiosities  and  has  become  an  article  of  commerce,  used 
for  many  other  purposes  than  the  reduction  of  aluminium,  though 
that  is  still  its  chief  use.  So  we  regard  the  manufacture  of 
sodium  as  a  separate  metallurgical  subject,  still  intimately  con- 

*  Polytechnisches  Central.  Blatt.,  1858,  p.  888. 

t  Chemical  News,  1860. 

J  German  Patent  (D.  R.  P.),  No.  14495  (1880). 


THE   MANUFACTURE   OF   SODIUM. 


145 


nected  with  that  of  aluminium,  but  yet  so  far  distinct  from  it  as 
to  deserve  a  metallurgical  treatise  of  its  own. 


Davy  to  Devllle  (1808-1855). 

Sodium  was  first  isolated  by  Davy  by  the  use  of  electricity  in 
the  year  1808.*  Later  Gay  Lussac  and  Thenard  made  it  by  de- 
composing at  a  very  high  temperature  a  mixture  of  sodium  car- 
bonate and  iron  filings,  f  In  1808,  also,  Curaudau  announced 
that  he  had  succeeded  in  producing  potassium  or  sodium  without 
using  iron,  simply  by  decomposing  their  carbonates  by  means  of 
animal  charcoal.  Briinner,  continuing  this  investigation,  used 
instead  of  animal  charcoal  the  so-called  black  flux,  the  product 
obtained  by  calcining  crude  tartar  from  wine  barrels.  He  was 
the  first  to  use  the  wrought-iron  mercury  bottles.  The  mixture 
was  heated  white  hot  in  a  furnace,  the  sodium  volatilized,  and 
was  condensed  in  an  iron  tube  screwed  into  the  top  of  the  flask, 
which  projected  from  the  furnace  and  was  cooled  with  water. 
In  Briinner's  experiments  he  only  obtained  three  per  cent,  of  the 
weight  of  the  mixture  as  metallic  sodium,  the  rest  of  the  metal 
being  lost  as  vapor. 

Donny  and  Mareska  gave  the  condenser  the  form  which  with 
a  few  modifications  it  retains  to-day. 
It   was  of  iron,  4  millimetres  thick,  FlS-  8- 

and  was  made  in  the  shape  of  a  book, 
having  a  length  of  about  100  centi- 
metres, breadth  50,  and  depth  6  (see 
Fig.  8).  This  form  is  now  so  well 
known  that  a  further  description  is 
unnecessary.  With  this  condenser  the 
greatest  difficulty  of  the  process  was 
removed,  and  the  operation  could  be 
carried  on  in  safety.  This  apparatus 

was  devised  and  used  by  Donny  and  Mareska  in  1854,  with  the 
supervision  of  Deville. 


*  Phil.  Trans.,  1808. 

f  Recherches  Physico-chemiques,  1810. 


10 


146  ALUMINIUM. 

Devitte's  Improvements  at  Javel  (1 855). 

The  followiDg  is  Deville's  own  description  of  the  attempts 
which  he  made  to  reduce  the  cost  of  producing  sodium.  As  far 
as  we  can  learn  these  experiments  were  commenced  in  1854,  but 
the  processes  about  to  be  given  are  those  which  were  carried  out 
at  Javel,  March  to  June,  1855.  As  the  description  contains  so 
many  allusions  to  the  difficulties  met  not  only  in  producing  but 
also  in  handling  and  preserving  sodium,  its  perusal  is  yet  of  value 
to  all  concerned  in  this  subject,  although  the  actual  methods  here 
described  have  been  superseded  by  much  more  economical  ones. 

Properties  of  sodium. — The  small  equivalent  of  sodium  and 
the  low  price  of  sodium  carbonate  should  long  since  have  caused 
it  to  be  preferred  to  potassium  in  chemical  operations,  but  a  false 
idea  prevailed  for  a  long  time  concerning  the  difficulties  accom- 
panying the  reduction.  When  I  commenced  these  researches  the 
cost  of  sodium  was  at  least  double  that  of  potassium.  In  this 
connection  I  can  quote  from  my  memoir  published  in  the  Ann. 
de  China,  et  de  Phys.,  Jan.  1,  1855  :  "I  have  studied  with  care 
the  preparation  of  sodium  and  its  properties  with  respect  to 
oxygen  and  the  air,  in  order  to  solve  the  difficulties  which  ac- 
company its  reduction  and  the  dangers  of  handling  it.  In  this 
latter  respect,  sodium  is  not  to  be  compared  to  potassium.  As 
an  example  of  how  dangerous  the  latter  is,  I  will  relate  that 
being  used  to  handle  sodium  and  wishing  once  to  replace  it  with 
potassium,  the  simple  rubbing  of  the  metal  between  two  sheets 
of  paper  sufficed  to  ignite  it  with  an  explosion.  Sodium  may  be 
beaten  out  between  two  sheets  of  paper,  cut  and  handled  in  the 
air  without  accident  if  the  fingers  and  tools  used  are  not  wet.  It 
may  be  heated  with  impunity  in  the  air,  even  to  its  fusing  point, 
without  taking  fire,  and,  when  melted,  oxidation  takes  place 
slowly,  and  only  at  the  expense  of  the  moisture  of  the  air.  I 
have  even  concluded  that  the  vapor  alone  of  sodium  is  inflam- 
mable, but  the  vivid  combustion  of  the  metal  can  yet  take  place 
at  a  temperature  which  is  far  below  its  boiling  point,  but  at  which 
the  tension  of  the  metallic  vapors  has  become  sensible."  I  will 
add  to  these  remarks  that  sodium  possesses  two  considerable  ad- 
vantages :  it  is  obtained  pure  at  the  first  operation,  and,  thanks 


THE  MANUFACTURE  OF  SODIUM.  147 

to  a  knack  which  I  was  a  long  time  in  finding  out,  the  globules 
of  the  metal  may  be  reunited  and  treated  as  an  ordinary  metal 
when  melting  and  casting  in  the  air.  I  have  thus  been  able  to 
dispense  with  the  distillation  of  the  raw  products  in  the  manu- 
facture— an  operation  which  had  become  to  be  believed  necessary, 
and  which  occasioned  a  loss  of  50  per  cent,  or  so  on  the  return 
without  appreciable  advantage  to  the  purity  of  the  metal.  The 
manufacture  of  sodium  is  in  no  manner  incumbered  by  the  carbu- 
retted  products,  or  perhaps  nitrides,  which  are  very  explosive  and 
render  the  preparation  of  potassium  so  dangerous.  I  ought  to 
say,  however,  that  by  making  potassium  on  a  large  scale  by  the 
processes  I  am  about  to  describe  for  sodium,  Rousseau  Bros,  have 
diminished  the  dangers  of  its  preparation  very  much,  and  practise 
the  process  daily  in  their  chemical  works. 

Method  employed. — The  method  of  manufacture  is  founded  on 
the  reaction  of  carbon  on  alkaline  carbonate.  This  method  has 
been  very  rarely  applied  to  sodium,  but  is  used  every  day  for 
producing  potassium.  Briinner's  process  is,  in  fact,  very  difficult 
to  apply,  great  trouble  being  met,  especially,  in  the  shape  of  con- 
denser used.  It  is  Donny  and  Mareska  who  have  mastered  the 
principles  which  should  guide  in  constructing  these  condensers. 

Composition  of  mixtures  used. — The  mixture  which  has  given 
me  excellent  results  in  the  laboratory  is — 

Sodium  carbonate           .         .         .         *         .         .     717  parts. 
Wood  charcoal       .         .         .         .         .     *    .         .     175     " 
Chalk 108     " 

1000 

Dry  carbonate  of  soda  is  used,  the  carbon  and  chalk  pulverized, 
the  whole  made  into  a  paste  with  oil  and  calcined  in  a  crucible. 
The  end  of  a  mercury  bottle,  cut  off,  serves  very  well,  and  can  be 
conveniently  closed.  Oil  may  be  used  altogether  in  place  of  char- 
coal, in  which  case  the  following  proportions  are  used  : — 

Sodium  carbonate 625  parts. 

Oil 280     " 

Chalk 95     " 

That  a  mixture  be  considered  good,  it  should  not  melt  at  the 
temperature  at  which  sodium  is  evolved,  becoming  liquid  at  this 


148  ALUMINIUM. 

point,  and  so  obstructing  the  disengagement  of  the  gas.*  But  it 
should  become  pasty,  so  as  to  mould  itself  evenly  against  the  lower 
side  of  the  iron  vessel  in  which  it  is  heated.  The  considerable 
latent  heat  required  by  carbonic  oxide  and  sodium  in  assuming 
the  gaseous  state  is  one  cause  of  cooling  which  retards  the  com- 
bustion of  the  iron.  When  soda  salt  is  introduced  in  place  of 
dried  soda  crystals,  the  mixture,  whatever  its  composition,  always 
melts,  the  gases  making  a  sort  of  ebullition,  the  workmen  saying 
that  the  apparatus  "sputters."  This  behavior  characterizes  a 
bad  mixture.  It  has  been  demonstrated  to  me  that  the  economy 
made  at  the  expense  of  a  material  such  as  carbonate  of  soda,  the 
price  of  which  varies  with  its  strength  in  degrees,  and  which 
forms  relatively  a  small  portion  of  the  cost  of  sodium,  is  annulled 
by  a  decrease  of  20  to  25  per  cent,  in  the  return  of  sodium.  The 
oil  used  ought  to  be  dry  and  of  long  flame.  It  acts  as  a  reducing 
agent,  and  also  furnishes  during  the  whole  operation  hydrogenous 
gases,  and  even,  towards  the  close,  pure  hydrogen,  which  help  to 
carry  the  sodium  vapor  rapidly  away  into  the  condenser,  and  to 
protect  the  condensed  metal  from  the  destructive  action  of  the 
carbonic  oxide.  Oil  renders  a  similar  service  in  the  manufacture 
of  zinc.  The  role  of  the  chalk  is  easy  to  understand.  By 
its  infusibility  it  decreases  the  liability  of  the  mixture  to  melt. 
Further,  it  gives  off  carbonic  acid,  immediately  reduced  by  the 
carbon  present  to  carbonic  oxide.  Now,  the  sodium  ought  to  be 
carried  rapidly  away,  out  of  the  apparatus,  because  it  has  the 
property  of  decomposing  carbonic  oxide,  which  is  simultaneously 
formed,  within  certain  limits  of  temperature,  especially  if  the 
sodium  is  disseminated  in  little  globules  and  so  presents  a  large 
surface  to  the  destructive  action  of  the  gas.  It  is  necessary,  then, 
that  the  metallic  vapors  should  be  rapidly  conducted  into  the  con- 
denser and  brought  into  the  liquid  state — not  into  that  state  com- 
parable to  "  flowers  of  sulphur,"  in  which  the  metal  is  very 
oxidizable  because  of  its  fine  division.  A  rapid  current  of  gas, 
even  of  carbonic  oxide,  actively  carries  the  vapors  into  the  con- 

*  It  seems  plain,  however,  granting  that  vapors  would  be  evolved  most 
freely  from  a  perfectly  infusible  charge,  that  a  pasty  condition,  such  as  is  recom- 
mended in  the  next  sentence,  would  be  the  worst  possible  state  of  the  charge 
for  evolving  gas,  being  manifestly  inferior  to  a  completely  fluid  bath. — J.  W.  R. 


THE   MANUFACTURE   OF   SODIUM.  149 

denser,  which  they  keep  warm  and  so  facilitate  the  reunion  of  the 
globules  of  sodium.  At  La  Glaciere  and  Nanterre  a  mixture 
was  used  in  which  the  proportion  of  chalk,  far  from  being  dimin- 
ished, was,  on  the  contrary,  increased.  The  proportions  used 
were — 

Sodium  carbonate        .         .         .         .40  kilos  =  597  parts. 

Oil 18      "     =  269     " 

Chalk 9      "     =  134     " 

67      "         1000 

This  quantity  of  mixture  ought  to  give  9.4  kilos  of  sodium, 
melted  and  cast  into  ingots,  without  counting  the  metal  di- 
vided and  mixed  with  foreign  materials,  of  which  a  good  deal  is 
formed.  This  return  would  be  one-seventh  of  the  weight  of 
the  mixture  or  one-quarter  of  the  sodium  carbonate  used. 

Use  of  these  mixtures. — The  carbonate  of  soda,  charcoal,  and 
chalk  ought  to  be  pulverized  and  sieved,  well  mixed  and  again 
sieved  in  order  to  make  a  very  intimate  mixture;  the  mixture 
ought  to  be  used  as  soon  as  possible  after  preparing,  that  it  may 
not  take  up  moisture.  The  mixture  may  be  put  just  as  it  is  into 
the  apparatus  where  it  should  furnish  sodium,  but  it  may  very 
advantageously  be  previously  calcined  so  as  to  reduce  its  volume 
considerably,  and  so  permit  a  greater  weight  being  put  into  the 
same  vessel.  I  believe  that  whenever  this  calcination  may  be 
made  with  economy,  as  with  the  waste  heat  of  a  furnace,  a  gain 
is  made  by  doing  so,  but  the  procedure  is  not  indispensable. 
However,  the  utility  of  it  may  be  judged  when  it  is  stated  that 
a  mercury  bottle  held  2  kilos  of  non-calcined  mixture,  but  3.6 
kilos  were  put  into  one  when  previously  calcined.  These  two 
bottles  heated  in  the  same  fire  for  the  same  time  gave  quantities 
of  sodium  very  nearly  proportional  to  the  weight  of  soda  in  them. 
In  working  under  the  direction  of  a  good  workman,  who  made 
the  bottles  serve  for  almost  four  operations,  I  have  been  able 
to  obtain  very  fine  sodium  at  as  low  a  price  as  9.25  francs  per 
kilo  ($0.84  per  pound).  In  the  manufacture  of  sodium  by  the 
continuous  process,  where  the  materials  may  be  introduced  red 
hot  into  the  apparatus,  this  preliminary  calcination  is  a  very 
economical  operation. 


150  ALUMINIUM. 

Apparatus  for  reducing,  condensing,  and  heating. — M.  Briin- 
ner  had  the  happy  idea  of  employing  mercury  bottles  in  manu- 
facturing potassium,  thus  the  apparatus  for  reduction  was  in  the 
hands  of  any  chemist,  and  at  such  a  low  price  that  any  one  has 
been  able  to  make  potassium  without  much  trouble.  These  bot- 
tles are  equally  suitable  for  preparing  sodium,  and  the  quantity 
which  may  be  obtained  from  such  apparatus  and  the  ease  with 
which  they  are  heated,  are  such  that  they  might  have  been,  used 
a  long  time  for  the  industrial  manufacture,  except  for  two  reasons 
which  tend  to  increase  the  price  of  these  bottles  continually. 
For  some  time  a  large  number  of  bottles  have  been  sent  to  the 
gold  workers  of  Australia  and  California,  also  large  quantities 
have  been  used  in  late  years  in  preparing  the  alkaline  metals ; 
these  two  facts  have  diminished  the  number  to  such  a  point  that 
from  0.5  to  1  franc  the  price  has  been  raised  to  2.5  or  3  francs. 
It  has  thus  become  necessary  to  replace  them,  which  has  been 
done  by  substituting  large  wrought  iron  tubes  which  have  the 
added  advantage  of  being  able  to  be  worked  continuously.  I 
will  first  describe  the  manufacture  in  mercury  bottles,  which  may 
still  be  very  advantageously  used  in  the  laboratory,  and  after- 
wards the  continuous  production  in  large  iron  cylinders  as  now 
worked  industrially. 

Manufacture  in  mercury  bottles. — The  apparatus  needed  is  com- 
posed of  a  furnace,  a  mercury  bottle,  and  a  condenser. 

The  form  of  furnace  most  suitable  is  a  square  shaft,  C  (Fig.  9)? 
the  sides  of  which  are  refractory  brick,  while  the  grate  G  ought 
to  have  movable  grate  bars,  the  furnace  being  connected  above 
with  a  chimney  furnishing  good  draft.  The  flue  F,  connecting 
with  the  chimney,  should  have  a  damper,  R,  closing  tightly  and 
should  lead  exactly  from  the  centre  of  the  top  of  the  shaft,  thus 
dividing  the  draft  equally  all  over  the  grate.  Coke  is  charged 
through  lateral  openings  at  0.  A  small  opening  closed  by  a 
brick  should  be  left  a  short  distance  above  the  grate  bars,  in 
order  to  poke  down  the  coke  around  the  bottle  should  it  not 
fall  freely.  The  space  between  the  grate  and  bottle  should 
always  be  full  of  fuel  in  order  to  keep  the  iron  of  the  bottle 
from  being  burnt.  In  front  of  the  furnace  is  a  square  opening, 
P,  closed  with  an  iron  plate,  which  has  a  hole  in  it  by  which 
the  tube  T  issues  from  the  furnace. 


151 


THE    MANUFACTURE    OF   SODIUM. 


The  mercury  bottle  is  supported  on  two  refractory  bricks, 
cut  on  their  top  side  to  the  curve  of  the  bottle.     These  should  be 

Fig.  9. 


at  least  20  centimetres  high,  to  maintain  between  the  grate  and 
bottle  a  convenient  distance.  The  illustration  gives  the  vertical 
dimensions  correctly,  but  the  horizontal  dimensions  are  somewhat 
shortened.  There  should  be  at  least  12  centimetres  between  the 
bottle  and  the  sides  of  the  furnace.  However,  all  these  dimen- 
sions should  vary  with  the  strength  of  the  chimney  draft  and  the 
kind  of  fuel  used ;  the  furnace  should  be  narrower  if  the  draft  is 
very  strong  and  the  coke  dense.  The  iron  tube  T7,  which  may 
conveniently  be  made  of  a  gun  barrel,  is  either  screwed  into  the 
bottle  or  it  may  be  simply  fitted  and  forced  into  place,  provided 
it  holds  tightly  enough.  It  should  be  about  5  to  6  centimetres 
long,  and  should  project  scarcely  1  centimetre  from  the  furnace. 
The  end  projecting  should  be  tapered  off  in  order  to  fit  closely 
into  the  neck  of  the  condenser. 

The  condenser  is  constructed  with  very  little  deviation  from 
that  given  by  Donny  and  Mareska  (see  Fig.  8,  p.  145).  I  have 
tried  my  best  to  make  this  apparatus  as  perfect  as  possible,  but 
have  always  reverted  to  the  form  described  by  those  authors ;  yet 
even  the  very  small  differences  I  have  made  are  indispensable 
and  must  be  rigidly  adhered  to  if  it  is  wished  to  get  the  best 


152 


ALUMINIUM. 


Fig.  10. 


results  obtainable.     Two  plates  of  sheet  iron,  2  to  3  millimetres 

thick,  are  taken  and  cut  into  the  shape  indicated  by  Fig.  10.  One 
plate,  A,  remains  flat  except  at  the  point  C, 
where  it  is  drawn  by  hammering  into  a 
semi-cylindrical  neck  of  about  25  millime- 
tres inside  diameter.  This  corresponds  with 
a  similar  neck  in  the  other  plate,  so  that  on 
joining  the  two  there  is  a  short  cylinder 
formed.  The  edges  of  the  plate  A  are 
raised  all  around  the  sides  about  5  to  6 
millimetres,  so  that  when  the  two  plates  are 

put  together  the  longitudinal  section  from  D  to  C  is  as  in  Fig. 

11.     As  to  the  end,  in  one  form  the  edge  was  not  turned  up,  leav- 

Fig.  11. 


Fig.  12.       Fig.  13. 


Fig.  14. 


ing  the  end  open  as  in  Fig.  12.  Another  form,  which  I  use 
when  wishing  to  let  the  sodium  accumulate  in  the  condenser  till 
it  is  quite  full,  is  made  by  turning  up  the  edge  at  the  end  all  but 
a  small  space  left  free,  thus  giving  the  end  the  appearance  of  Fig. 
13,  this  device  also  being  shown  in  Fig.  10.  The  gas  evolved 
during  the  reaction  then  escapes  at  the  hole  0.  The  most  rational 
arrangement  of  the  apparatus  is  that  shown  in  Fig.  14.  In  this 
condenser  the  lower  part,  instead  of  being  horizontal,  is  inclined, 
and  the  end  having  two  openings,  0  and  #',  the  sodium  trickles 
out  at  the  lower  one  as  it  condenses,  while  the  gas  escapes  by  the 
slightly  larger  upper  opening.  In  placing  the  plates  together, 
the  raised  edges  are  washed  with  lime  so  as  to  form  a  good  joint 
with  the  flat  plate,  and  the  plates  are  kept  together  by  strong 
pressure  grips. 

To  conduct  the  operation,  the  bottles  are  filled  entirely  with 


THE   MANUFACTURE   OF   SODIUM.  153 

mixture,  the  tube  T  adjusted,  and  then  placed  on  the  two  sup- 
ports, there  being  already  a  good  bed  of  fire  on  the  grate.  The 
front  is  put  up,  the  shaft  filled  with  coke,  and  the  damper  opened. 
The  gases  disengaged  from  the  bottle  are  abundant,  of  a  yellow 
color ;  at  the  end  of  half  an  hour  white  fumes  of  carbonate  of 
soda  appear.  The  condenser  should  not  yet  be  attached,  but  it 
should  be  noted  if  any  sodium  condenses  on  a  cold  iron  rod  pushed 
into  the  tube,  which  would  be  indicated  by  it  fuming  in  the  air. 
As  soon  as  this  test  shows  that  sodium  is  being  produced  the 
condenser  is  attached  and  the  fire  kept  quite  hot.  The  condenser 
soon  becomes  warm  from  the  gases  passing  through  it,  while  the 
sodium  condenses  and  flows  out  at  the  end  D  (Fig.  9).  It  is 
received  in  a  cast-iron  basin  L,  in  which  some  non- volatile 
petroleum  is  put.  When  at  the  end  of  a  certain  time  the  con- 
denser becomes  choked,  it  is  replaced  by  another  which  has  been 
previously  warmed  up  to  200°  or  300°  by  placing  it  on  top  of 
the  furnace.  If  the  closed  condenser  is  used,  care  must  be  taken 
to  watch  when  it  becomes  full,  on  the  point  of  running  from  the 
upper  opening,  and  the  condenser  then  replaced  and  plunged  into 
a  cast-iron  pot  full  of  petroleum  at  a  temperature  of  150°.  The 
sodium  here  melts  at  the  bottom  of  this  pot  and  is  ladled  out  at 
the  end  of  the  day.  The  oil  is  generally  kept  up  to  150°  by  the 
hot  condensers  being  plunged  in  constantly.  The  pot  ought  to 
have  a  close  cover,  to  close  it  in  case  the  oil  takes  fire ;  the  ex- 
tinction of  the  fire  can  thus  be  assured  and  no  danger  results.  If 
the  oil  fires  just  as  a  condenser  is  being  introduced,  the  sodium  is 
run  out  in  the  air  without  igniting,  the  only  drawback  being  that 
the  condenser  must  be  cleaned  before  using  again.  This  method 
occasions  a  large  loss  of  oil,  however,  and  has  been  completely 
abandoned  for  the  other  form  of  condensers.  When  the  opera- 
tion proceeds  well  only  pure  sodium  is  obtained,  the  carbonized 
products  which  accompany  in  so  provoking  a  manner  the  pre- 
paration of  potassium  not  occurring  in  quantity  sufficient  to  cause 
any  trouble.  Before  using  a  condenser  a  second  time  it  is  put  on 
a  grating  over  a  basin  of  petroleum  and  rubbed  with  a  chisel- 
pointed  tool  in  order  to  remove  any  such  carbonized  products. 
From  time  to  time  this  material  is  collected,  put  into  a  mercury 
bottle,  and  heated  gently.  The  oil  first  distils,  and  is  condensed 


154  ALUMINIUM. 

in  another  cold  bottle.  The  fire  is  then  urged,  a  condenser  at- 
tached, and  the  operation  proceeds  as  with  a  fresh  charge,  much 
sodium  being  thus  recovered. 

The  raw  sodium  is  obtained  from  the  bottles  in  quantities  of 
over  half  a  kilo ;  it  is  perfectly  pure,  dissolving  in  absolute  al- 
cohol without  residue.  It  is  melted  and  moulded  into  ingots  just 
as  lead  or  zinc.  The  operation  I  have  described  is  executed  daily, 
and  only  once  has  the  sodium  ignited.  To  prevent  such 
accidents  it  is  simply  necessary  to  keep  water  away  from  the  ap- 
paratus. The  reduction  of  carbonate  of  soda  and  the  production 
of  sodium  are  such  easy  operations  that  when  tried  by  those  con- 
versant with  the  manufacture  of  potassium  or  who  have  read 
about  the  difficulties  of  the  production  of  sodium,  success  is  only 
gained  after  several  attempts — the  failure  being  due  solely  to  ex- 
cess of  precautions.  The  reduction  should  be  carried  on  rapidly, 
so  that  a  bottle  charged  with  two  kilos  of  mixture  may  be  heated 
and  emptied  in,  at  most,  two  hours.  It  is  unnecessary  to  prolong 
the  operation  after  the  yellow  flame  stops  issuing  from  the  con- 
denser, for  no  more  sodium  is  obtained  and  the  bottle  may  fre- 
quently be  destroyed.  The  temperature  necessary  for  the  re- 
duction is  not  so  high  as  it  has  been  so  far  imagined.  M.  Rivot, 
who  has  assisted  in  these  experiments,  thinks  that  the  bottles  are 
not  heated  higher  than  the  retorts  in  the  middle  of  the  zinc  fur- 
naces at  Vielle  Montagne.  I  have  been  even  induced  to  try  cast- 
iron  bottles,  but  they  did  not  resist  the  first  heating,  without  doubt 
because  they  were  not  protected  from  the  fire  by  any  luting  or 
covering.  But  I  was  immediately  successful  in  using  cast-iron 
bottles  decarburised  by  the  process  used  for  making  malleable 
castings.  The  mercury  bottles  heated  without  an  envelope  ought 
to  serve  three  or  four  operations  when  entrusted  to  a  careful 
workman.  Besides  all  these  precautions,  success  in  this  work  de- 
pends particularly  on  the  ability  and  experience  of  the  workman, 
who  can  at  any  time  double  the  cost  of  the  sodium  by  careless- 
ness in  managing  the  fire. 

.  Continuous  manufacture  in  cylinders. — It  might  be  thought  that 
by  increasing  proportionately  in  all  their  parts  the  dimensions  of 
the  apparatus  just  described  it  would  be  easy  to  produce  much 
larger  quantities  of  sodium.  This  idea,  which  naturally  presented 


THE   MANUFACTURE   OF   SODIUM. 


155 


itself  to  me  at  once,  has  been  the  cause  of  many  unfruitful  at- 
tempts, into  the  details  of  which  I  will  not  enter.  I  must,  how- 
ever, explain  some  details  which  may  appear  insignificant  at  first 
sight,  but  which  were  necessitated  during  the  development  of  the 
process.  For  instance,  it  will  perhaps  look  irrational  for  me  to 
keep  the  same  sized  outlet  tubes  and  condensers  that  were  used 
with  the  mercury  bottles,  for  tubes  five  times  as  large ;  but  I 
was  forced  to  adopt  this  arrangement  after  trying  the  use  of  tubes 
and  condensers  of  all  sizes ;  indeed,  it  is  fortunate  for  the  suc- 
cess of  the  operation  that  this  was  so,  for  it  became  very  injurious 
to  the  workmen  to  handle  the  large  and  weighty  apparatus  in  the 
face  of  a  large  sodium  flame. 

The  mixture  of  sodium  carbonate  and  carbon  is  made  in  the 
manner  already  described.  I  would  say  again  that  a  previous 
strong  calcination  of  the  materials  presents  a  great  advantage, 
not  only  because  it  permits  putting  a  much  larger  weight  into  the 
retorts  at  once  but  also  that,  being  more  compact,  the  mixture 
will  not  rise  as  powder  and  be  violently  thrown  out  of  the  strongly- 

Fig.  15. 


heated  retorts.  The  mixture  should  also  be  calcined  as  needed 
and  used  to  fill  the  tubes  while  still  red  hot.  When  cold,  un- 
calcined  mixture  is  used,  it  is  put  into  large  cartridges  of  thick 
paper  or  canvas,  8  centimetres  diameter  and  35  centimetres  long. 


156  ALUMINIUM. 

The  furnace  and  tubes  are  shown  in  section  in  Fig.  15.  The 
tubes  Tare  120  centimetres  long,  14  centimetres  inside  diameter, 
and  10  to  12  millimetres  in  thickness.  They  are  formed  from 
one  piece  of  boiler  iron,  bent  and  welded  along  one  side.  The 
iron  plate  P  which  closes  one  end  is  about  2  centimetres 
thick,  and  pierced  on  one  of  its  edges  quite  close  to  the  side  of  the 
cylinder  by  a  hole  in  which  is  screwed  or  fitted  an  iron  tube,  L, 
5  to  6  centimetres  long  and  15  to  20  millimetres  inside  diameter, 
and  tapering  off  at  the  end  to  fit  into  the  condenser  neck.  The 
other  end  of  the  tube  is  closed  by  an  iron  plug,  0,  terminated  by 
a  knob.  The  welded  side  of  the  tube  is  kept  uppermost.  These 
iron  tubes  should  not,  like  the  mercury  bottles,  be  heated  in  the 
bare  fire ;  it  is  necessary  to  coat  them  with  a  resistant  luting 
which  is  itself  enveloped  by  a  refractory  jacket  1  centimetre 
thick,  22  centimetres  interior  diameter,  and  the  same  length  as  the 
retorts.  This  protection  is  commenced  by  plastering  the  retorts 
over  with  a  mixture  of  equal  parts  of  raw  clay  and  stove  ashes, 
which  have  been  made  into  a  paste  with  water  and  as  much  sand 
worked  into  the  mixture  as  it  will  take  without  losing  its  plas- 
ticity, also  adding  some  horse  manure.  This  luting  should  be 
dried  slowly,  and  the  tube  thus  prepared  is  introduced  into  the 
refractory  jacket,  the  open  space  between  the  two  being  filled 
with  a  powdered  refractory  brick.  Finally,  luting  is  put  on  the 
iron  plate  P9  so  that  no  part  of  it  is  exposed  to  the  flame. 

The  furnace  I  have  used  is  a  reverberatory,  but  I  do  not  re- 
commend its  use  without  important  modifications  because  it  does 
not  realize  all  the  conditions  of  easy  and  economic  heating.  The 
grate  is  divided  into  two  parts  by  a  little  wall  of  refractory  brick, 
on  which  the  middle  of  the  reduction  cylinders  rests.  The  tubes 
are  thus  seen  to  be  immediately  over  the  bed  of  fuel.  The  top  of 
the  bridge  is  a  little  higher  than  the  upper  edge  of  the  cylinders, 
this  and  the  very  low  arch  making  the  flame  circulate  better  all 
around  the  tubes.  A  third  cylinder  might  easily  be  placed  above 
these  two,  and  be  heated  satisfactorily,  without  any  more  fuel  be- 
ing burnt.  This  reverberatory  receives  on  its  bed  the  mixtures  to 
be  calcined,  placed  in  cast-iron  or  earthen  pots  according  to  their 
composition.  When  the  furnace  is  kept  going  night  and  day  pro- 
ducing sodium,  the  temperature  rises  on  the  bed  to  clear  cherry- 


THE    MANUFACTUKE   OF   SODIUM.  157 

red,  and  experience  has  shown  that  other  reducing  cylinders 
might  be  placed  there,  under  such  conditions,  and  be  heated 
sufficiently  for  the  reduction. 

All  that  I  have  said  of  the  manufacture  of  sodium  in  mercury 
bottles  applies  equally  to  its  manufacture  in  cylinders.  The  only 
difference  consists  in  the  charging  and  discharging,  and  I  have 
only  to  add  several  precautions  to  be  taken.  On  introducing  the 
cartridges  containing  uncalcined  mixture,  only  8  to  9  kilos  can 
be  heated  at  once ;  double  as  much  can  be  used  of  previously 
calcined  mixture.  The  plug  0  is  put  in  place,  not  so  tightly 
that  it  cannot  easily  be  taken  out  again  ;  a  little  luting  stops  all 
leakages  which  show  themselves.  The  reduction  lasts  about 
four  hours.  When  it  is  finished,  a  little  water  is  thrown  on 
the  plug  0,  and  it  is  easily  loosened  and  removed.  On  looking 
into  the  cylinder,  the  cartridges  are  seen  to  have  kept  their  shape, 
but  have  shrunken  so  much  that  their  diameter  is  only  about  2 
to  3  centimetres ;  they  are  very  spongy.  This  shows  that  the 
mixture  has  not  melted  ;  the  remainder  is  principally  lime  and 
carbon,  and  free  from  sodium  carbonate.  While  opening  the 
cylinder,  a  bright-red-hot  iron  is  thrust  into  the  outlet  tube  L,  to 
keep  dirt  from  getting  into  it,  and  it  is  kept  in  until  the  charging 
is  finished.  The  cartridges  are  put  in  by  means  of  semi-cylin- 
drical shovels.  The  sudden  heating  of  the  mixture  disengages 
soda  dust  from  uncalcined  mixtures,  which  is  very  disagreeable 
to  the  workmen.  The  cylinders  are  closed,  and  when  the  sodium 
flame  appears  at  the  outlet  tube  the  condenser  is  attached,  and 
the  operation  proceeds  as  already  described. 

The  envelopes  of  the  cylinders  are  thick  enough  to  prevent 
the  distillation  of  the  sodium  being  in  any  way  affected  by  the 
accidental  causes  of  cooling  of  the  fire.  So  when  fresh  fuel  is 
charged  or  the  door  of  the  reverberatory  is  opened  causing  the 
draft  to  cease  almost  entirely  in  the  fire-place,  the  operation 
should  not  suffer  by  these  intermittences  provided  that  they  are 
not  too  prolonged.  In  short,  when  operating  in  cylinders,  the 
production  of  sodium  is  easier,  less  injurious  to  the  workmen, 
and  less  costly  in  regard  to  labor  and  fuel  than  when  working 
with  mercury  bottles.  At  times,  after  working  a  fortnight  with 
many  interruptions  dangerous  for  the  apparatus,  my  experiment 


158  ALUMINIUM. 

has  been  suddenly  ended.  The  furnace  was  intact;  the  envelopes 
of  the  tubes  were  split  open,  and  the  luting  on  the  tubes  found  to 
be  compact  and  coherent  but  without  traces  of  fusion,  showing 
perfect  resistance.  The  iron  tubes  meanwhile  had  not  suffered 
inside  or  out,  and  seemed  as  though  they  would  last  indefinitely. 
I  attribute  this  success  to  the  particular  care  given  to  the  com- 
position of  the  jackets,  and  to  the  perfection  with  which  the  tubes 
had  been  welded.  Only  on  one  of  the  tubes  was  a  very  slight 
crack  found  on  a  part  not  the  most  highly  heated,  and  not  suffi- 
cient to  cause  the  tube  to  be  discarded. 

Tissier  Bros*  method  of  procedure  (1856).  As  related  in  the 
historical  treatment  of  the  subject  (p.  22),  Deville  charged  the 
Tissier  Bros,  with  appropriating  from  him  the  process  for  the 
continuous  production  of  sodium  in  cylinders,  which,  as  just 
given,  was  devised  during  the  experiments  at  Javel.  On  the 
other  hand,  the  Tissier  Bros,  asserted  their  right  to  the  process, 
patenting  it,  and  using  it  in  the  works  started  at  Rouen  in  the 
latter  part  of  1 855.  The  following  details  are  taken  from  Tissier's 
"  Recherche  de  F  Aluminium,"  only  such  being  selected  as  sup- 
plement Deville's  description  which  has  just  been  given. 

The  sodium  carbonate  is  first  well  dried  at  a  high  temperature, 
then  mixed  with  well-dried  pulverized  charcoal  and  chalk,  ground 
to  the  finest  powder,  the  success  of  the  operation  depending  on 
the  fineness  of  this  mixture.  The  proportions  of  these  to  use  are 
various.  One  simple  mixture  is  of — 

Sodium  carbonate 566 

Coal .244 

Chalk .       95 

Coke 95 

1000 
Another  contains — 

Sodium  carbonate .615 

Coal 277 

Chalk 108 

1000 

The  addition  of  chalk  has  the  object  of  making  the  mixture 
less  fusible  and  more  porous,  but  has  the  disadvantage  that  the 


THE   MANUFACTURE   OF   SODIUM.  159 

residue  remaining  in  the  retort  after  the  operation  is  very  impure, 
and  it  is  impossible  to  add  any  of  it  to  the  succeeding  charge  ; 
and  also,  some  of  it  being  reduced  to  caustic  lime  forms  caustic 
alkali  with  some  sodium  carbonate,  which  is  then  lost.  When 
the  mixture  is  well  made  it  is  subjected  to  a  preliminary  calcin- 
ation. This  is  done  in  cast-iron  cylinders,  two  of  which  are 
placed  side  by  side  in  a  furnace  and  heated  to  redness  (see  Fig. 
16).  This  is  continued  till  all  the  moisture,  carbonic  acid,  and 

Fig.  16. 


any  carburetted  hydrogen  from  the  coal  cease  coming  off.  The 
mass  contracts,  becomes  white  and  somewhat  dense,  so  that  a 
larger  amount  of  the  mixture  can  now  be  treated  in  the  retorts 
where  the  sodium  is  evolved.  As  soon  as  the  outcoming  gases 
burn  with  a  yellow  flame,  showing  sodium  coming  off,  the  calcin- 
ation is  stopped.  The  mixture  is  then  immediately  drawn  out 
on  to  the  stone  floor  of  the  shop,  where  it  cools  quickly  and  is 
then  ready  for  the  next  operation.  This  calcination  yields  a 
mixture  which  without  any  previous  reactions  is  just  ready  to 
evolve  sodium  when  brought  to  the  necessary  temperature.  This 
material  is  made  into  a  sort  of  cylinder  or  cartridge  and  put 
into  the  decomposition  retorts  (see  Fig.  15).  The  charging  should 
be  done  quickly.  The  final  retorts  are  of  wrought-iron,  since 
cast-iron  would  not  stand  the  heat.  At  each  end  this  retort  is 
closed  with  wrought-iron  stoppers  and  made  tight  with  fire-clay. 
Through  one  stopper  leads  the  pipe  to  the  condenser,  the  other 
stopper  is  the  one  removed  when  the  retort  is  to  be  recharged. 
These  retorts  are  placed  horizontally  in  rows  in  a  furnace.  Usu- 
ally four  are  placed  in  a  furnace,  preferably  heated  by  gas,  such 
as  the  Siemens  regenerative  furnace  or  Bicheroux,  these  being 


160  ALUMINIUM. 

much  more  economical.  In  spite  of  all  these  precautions  the 
retorts  will  be  strongly  attacked,  and  in  order  to  protect  them 
from  the  destructive  action  of  a  white  heat  for  seven  or  eight 
hours  they  are  coated  with  some  kind  of  fire-proof  material. 
The  best  for  this  purpose  is  graphite,  which  is  made  into  cylin- 
ders inclosing  the  retorts,  and  which  can  remain  in  place  till  the 
furnace  is  worn  out.  These  graphite  cylinders  not  only  protect 
the  iron  retorts,  but  prevent  the  diffusion  of  the  gaseous  products 
of  the  reaction  into  the  hearth,  and  so  support  the  retorts  that 
their  removal  from  the  furnace  is  easily  accomplished.  Instead 
of  these  graphite  cylinders  the  retorts  may  be  painted  with  a 
mixture  that  melts  at  white  heat  and  so  enamels  the  outside.  A 
mixture  of  alumina,  sand,  yellow  earth,  borax,  and  water-glass 
will  serve  very  well  in  many  cases.  We  would  remark  that  the 
waste  gases  from  this  furnace  can  be  used  for  the  calcining  of  the 
mixture,  or  even  for  the  reduction  of  the  aluminium  by  sodium 
where  the  manufacture  of  the  former  is  connected  with  the 
making  of  the  sodium. 

As  for  the  reduction  of  the  sodium,  the  retort  is  first  heated  to 
redness,  during  which  the  stopper  at  the  condenser  end  of  the 
retort  is  left  off.  The  charge  is  then  rapidly  put  in,  and  the 
stopper  at  once  put  in  place.  The  reaction  begins  almost  at  once 
and  the  operation  is  soon  under  full  headway,  the  gases  evolved 
burning  from  the  upper  slit  of  the  condenser  tube  with  a  flame  a 
foot  long.  The  gases  increase  in  volume  as  the  operation  con- 
tinues, the  flame  becoming  yellower  from  sodium  and  so  intensely 
bright  as  to  be  insupportable  to  look  at.  Now  has  come  the 
moment  when  the  workman  must  quickly  adapt  the  condenser  to 
the  end  of  the  tube  projecting  from  the  retort,  the  joint  being 
greased  with  tallow  or  paraffin.  The  sodium  collects  in  this  in 
a  melted  state  and  trickles  out.  The  length  of  the  operation 
varies,  depending  on  the  intensity  of  the  heat  and  the  quantity 
of  the  mixture ;  a  charge  may  sometimes  be  driven  over  in  two 
hours,  and  sometimes  it  takes  eight.  We  can  say,  in  general,  that 
if  the  reaction  goes  on  quickly  a  somewhat  larger  amount  of 
sodmm  is  obtained.  The  higher  the  heat  used,  however,  the 
quicker  the  retorts  are  destroyed.  The  operation  requires  con- 
tinual attention.  From  time  to  time,  a  workman  with  a  prod 


THE   MANUFACTURE   OF   SODIUM.  161 

opens  up  the  neck  of  the  condenser.  But  if  care  is  not  taken 
the  metal  overflows ;  if  this  happens,  the  metal  overflowing  is 
thrown  into  some  petroleum,  while  another  man  replaces  the  con- 
denser with  an  empty  one.  The  operation  is  ended  when  the 
evolution  of  gas  ceases  and  the  flame  becomes  short  and  feeble, 
while  the  connecting  tube  between  the  retort  and  condenser  keeps 
clean  and  does  not  stop  up.  As  soon  as  this  occurs,  the  stopper 
at  the  charging  end  is  removed,  the  charge  raked  out  into  an  iron 
car,  and  a  new  charge  being  put  in,  the  operation  continues. 
After  several  operations  the  retorts  must  be  well  cleaned  and 
scraped  out.  The  sodium  thus  obtained  is  in  melted  bits  or 
drops,  mixed  with  carbon  and  sodium  carbonate.  It  must,  there- 
fore, be  cleaned,  which  is  done  by  melting  it  in  a  wrought-iron 
kettle  under  paraffin  with  a  gentle  heat,  and  then  casting  it  into 
the  desired  shapes.  The  sodium  is  kept  under  a  layer  of  oil  or 
any  hydrocarbon  of  high  boiling  point  containing  no  oxygen. 
Tissier  gives  the  reaction  as — 

Na'CO3  4-  2C= SCO  +  2Na. 

The  sodium  is  condensed,  while  the  carbonic  oxide,  carrying 
over  some  sodium,  burns  at  the  end  of  the  apparatus.  This 
would  all  be  very  simple  if  the  reaction  of  carbonic  oxide  on 
sodium  near  the  condensing  point  did  not  complicate  matters,  pro- 
ducing a  black,  infusible  deposit  of  sodium  monoxide  (Na2O)  and 
carbon,  which  011  being  melted  always  gives  rise  to  a  loss  of  sodium. 

Devillds  Improvements  at  La  Glacier e  (1857). 

At  this  works  Deville  tried  the  continuous  process  of  manu- 
facturing sodium  in  cylinders  on  a  still  larger  scale,  with  the  fol- 
lowing results,  as  described  by  Deville  himself: — 

We  made  no  change  in  the  composition  of  the  mixtures  used 
from  those  already  described,  or  in  the  form  or  size  of  the  iron 
tubes  or  the  method  of  condensation ;  but  we  worked  with  six 
cylinders  at  a  time  in  a  furnace  similar  to  the  puddling  furnaces 
of  M.  Guadillot,  the  tubes  being  protected  by  refractory  envelopes. 
The  cylinders  were  so  arranged  on  the  hearth  that  the  flame  bathed 
all  parts  of  their  surface.  A  low  brick  wall  extends  down  the 
11 


162  ALUMINIUM. 

centre  of  the  hearth,  supporting  the  middle  of  the  cylinders,  which 
extend  across  it.  The  hearth  is  well  rammed  with  refractory  sand, 
and  the  space  between  it  and  the  bottom  of  the  cylinders  serves 
as  a  passage  way  for  most  of  the  flame. 

Our  six  cylinders  worked  satisfactorily  for  five  days.  We 
were  able  to  observe  that  they  were  all  heated  with  remarkable 
uniformity,  and  that  the  heat  was  sufficient  all  round  them.  It 
also  appeared  that  the  rear  end  of  the  cylinders  required  only  a 
hermetic  seal.  Indeed,  as  soon  as  the  operation  was  well  under 
way  and  sodium  distilling  off,  some  of  it  condensed  and  oxidized  in 
the  cool  parts  of  the  apparatus,  forming  a  sort  of  plug  of  carbonate 
and  carbides  of  sodium  which  the  vapor  and  gases  could  no  longer 
penetrate.  We  were  thus  able  for  a  long  time  to  distil  sodium 
away  from  one  of  our  tubes  which  was  entirely  opened  at  the 
rear. 

This  new  furnace  worked  so  well  that  we  were  hopeful  of  com- 
plete success  when  an  accident  happened  which  compelled  the 
stopping  of  the  experiment.  The  iron  tubes  had  been  ordered 
1.20  metres  long,  the  size  of  the  hearth  calculated  accordingly, 
but  they  were  delivered  to  us  only  1.05  metres  long.  We  made 
use  of  these,  with  the  result  that  the  rear  ends  became  red-hot 
during  the  operation  and  allowed  sodium  vapors  to  leak  through. 
These  leaked  through  the  luting,  and  escaping  into  the  furnace 
melted  the  envelopes  very  rapidly. 

In  another  attempt,  in  which  this  fault  was  avoided,  we  were 
unsuccessful  because  the  envelopes  gave  way  at  the  first  heating 
up,  both  they  and  the  iron  tubes  being  of  inferior  quality.  We 
were  considerably  inconvenienced  by  the  failure  of  these  experi- 
ments, which  caused  considerable  expense  and  gave  no  very  de- 
finite results.  Just  then  a  new  sort  of  apparatus  was  devised,  a 
description  of  which  is  given  later  on.  It  will  be  seen  that  we 
were  compelled  to  employ  tubes  of  very  small  value,  so  that  their 
destruction  in  case  of  accident  involved  no  great  loss,  and  to  heat 
each  one  by  an  independent  fire,  so  that  the  stoppage  or  de- 
struction of  one  cylinder  would  not  necessitate  the  stoppage  or 
endanger  the  safety  of  the  neighboring  ones. 

Cast-iron  vessels. — Deville  tried  at  La  Glaciere,  as  well  as  at 
Javel,  to  utilize  cast-iron  vessels  for  producing  sodium.  Deville 


THE   MANUFACTURE   OF   SODIUM.  163 

states  the  difficulties  which  caused  their  use  to  be  unsuccessful  to 
be  as  follows  : — 

The  result  was  always  unfavorable.  Sodium  is  obtained,  but 
as  soon  as  its  production  becomes  rapid  the  vessel  melts  and  the 
operation  is  quickly  ended.  This  follows  because  the  temperature 
necessary  for  the  production  of  the  metal  is  far  from  being  suffi- 
cient for  producing  it  in  large  quantities  at  once ;  and  we  know 
that  this  is  the  one  condition  for  condensing  the  sodium  well  and 
obtaining  it  economically.  This  observation  led  me  to  think 
that  by  diminishing  very  much  the  temperature  of  the  furnace, 
large  apparatus  of  cast-iron  with  large  working  surface  could  be 
used,  thus  making  at  a  time  a  large  amount  of  metallic  vapor 
which  could  be  condensed  in  recipients  of  ordinary  size.  The 
whole  large  apparatus  would  thus  have  the  output  of  a  smaller  one 
worked  at  a  higher  temperature.  My  experience  has  shown  me 
that  in  large  sized  tubes  heated  to  a  low  temperature  there  is 
formed  in  a  given  time  about  as  much  sodium  as  from  a  single 
mercury  bottle  at  a  much  higher  heat.  This  is  the  reason  why 
larger  condensers  are  not  necessary  with  the  larger  tubes.  Be- 
fore knowing  this  fact,  I  tried  a  large  number  of  useless  experi- 
ments to  determine  the  size  of  condensers  suitable  for  large  ap- 
paratus. It  is  on  this  principle  that  I  have  long  been  endeavor- 
ing to  make  sodium  without  working  at  high  temperatures  and 
using  less  costly  and  more  easily  protected  apparatus. 

Improvements  used  at  Natiterre  (1859). 

The  method  used  here  was  exactly  that  already  described,  the 
improvements  being  solely  in  details  of  the  apparatus.  These 
are  described  by  Devil le  as  follows  : — 

The  experiments  made  at  Javel  and  the  continuous  process 
used  at  Glaciere  have  shown  us  in  the  clearest  manner  the  abso- 
lute necessity  of  efficient  protection  for  the  iron  cylinders,  for 
without  this  protection  the  method  cannot  be  practised  with 
economy.  Further,  experiments  in  this  direction  are  very  costly, 
for  the  failure  of  a  tube  stops  the  working  of  a  large  number  of 
cylinders  and  often  compromises  the  brick  work  of  the  furnace 
itself.  We  therefore  came  to  the  conclusion  that  for  making  the 


164  ALUMINIUM. 

small  quantity  of  sodium  we  required,  300  to  500  kilos  a  month, 
it  would  be  better  to  employ  smaller  apparatus  independent  of 
each  other  and  easy  to  replace. 

The  iron  tubes  are  made  of  thinner  iron  and  at  very  little 
expense,  by  taking  a  sheet  of  iron,  curving  it  into  a  cylinder  and 
rivetting  the  seam.  This  tube  resembles  very  closely  those  used 
at  Javel,  shown  in  Fig.  15,  but  of  smaller  dimensions.  It  is 
closed  at  each  end  by  cast-iron  plugs,  one  of  which  has  a  hole  for 
the  outlet  tube.  These  cylinders  are  filled  with  sodium  mixture 
and  placed  in  furnaces  of  the  form  of  Fig.  9,  except  it  is  neces- 
sary to  have  openings  in  the  back  and  front  of  the  furnace  so 
that  the  cast-iron  plugs  closing  the  cylinders  may  be  outside,  to 
prevent  their  melting.  We  used  coke  at  first  for  fuel,  fed  around 
the  cylinders,  but  M.  Morin  has  since  placed  the  tubes  out  of 
direct  contact  with  the  fuel,  uses  soft  coal,  and  heats  the  tubes  by 
contact  with  the  flame  and  by  radiation.  In  the  latest  form  used, 
two  cylinders  are  placed  in  each  furnace,  and,  in  general,  they 
serve  for  two  or  three  operations.  All  that  has  been  said  in  con- 
nection with  the  manufacture  in  mercury  bottles  is  immediately 
applicable  to  the  manufacture  in  cylinders  of  this  kind,  the  capaci- 
ties of  which  may  vary  from  two  to  six  or  eight  litres,  without 
any  change  in  the  manner  of  using  them.  We  have,  however, 
adopted  altogether  condensers  of  cast  iron.  The  neck  is  cylin- 
drical and  belongs  only  to  one-half  of  the  apparatus,  the  neck 
end  of  the  other  plate  being  bevelled  and  fitting  closely  against 
a  recess  in  the  other  plate. 

The  foregoing  shows  the  sodium  industry  as  it  was  perfected 
by  Deville,  in  1859,  and  as  it  remained  for  twenty-five  years 
without  sensible  change.  The  cost  of  sodium  by  this  process  is 
stated  to  have  been,  in  1872,  as  follows : — 

Manufacture  of  one  kilo  of  sodium. 

Soda      .       .       .9.35  kilos  @  32  fr.  per  100  kilos  =  3  fr.  9  cent. 

Coal  .  .  .74.32  "  "1.40"  "  "  =1"  4  " 

Wages  .  .  .  .  1  "  73  " 
Expenses  .  .  .  3  "  46  " 

Total        .       .       .       .  11  "  32    " 

which  is  equal  to  $1  per  Ib.  The  larger  part  of  the  expense  ac- 
count is  the  cost  of  retorts  or  tubes  in  which  the  operation  takes 


THE   MANUFACTURE   OF   SODIUM.  165 

place,  and  which  are  so  quickly  destroyed  that  the  replacing  of 
them  forms  nearly  one-quarter  of  the  cost  of  the  metal. 

Minor  Improvements  (1859—1888). 

R.  Wagner*  uses  paraffin  in  preference  to  paraffin  oil  in  which 
to  keep  the  sodium  after  making  it.  Only  pure  paraffin,  which 
has  been  melted  a  long  time  on  a  water  bath,  and  all  its  water 
driven  off,  can  be  used.  The  sodium  to  be  preserved  is  dipped  in 
the  paraffin  melted  on  a  water  bath  and  kept  at  no  higher  heat 
than  55°,  and  the  metal  is  thereby  covered  with  a  thick  coat  of 
paraffin  which  protects  it  from  oxidation,  and  may  then  be  put 
up  in  wooden  or  paper  boxes.  When  the  metal  is  to  be  used, 
it  is  easily  freed  from  paraffin  by  simply  warming  it,  since  sodium 
melts  at  95°  to  96°  C.,  and  the  paraffin  at  50°  to  60°. 

The  reduction  of  potassium  carbonate  by  carbon  requires  a 
much  less  degree  of  heat  than  that  of  sodium  carbonate,  and, 
therefore,  many  attempts  have  been  made  to  reduce  potassium 
and  sodium  together,  under  circumstances  where  sodium  alone 
would  not  be  reduced.  Dumasf  added  some  potassium  carbonate 
to  the  regular  sodium  mixture ;  and  separated  the  sodium  and 
potassium  from  each  other  by  a  slow,  tedious  oxidation.  R.  Wag- 
nerj  made  a  similar  attempt.  He  says  that  not  only  does  the 
reduction  of  both  metals  from  a  mixture  of  their  carbonates 
with  carbon  work  easier  than  sodium  carbonate  alone  with 
carbon,  but  even  caustic  soda  may  be  used  with  potassium  car- 
bonate and  carbon.  Also,  the  melting  point  of  potassium  and 
sodium  alloyed  is  much  lower  than  that  of  either  one  alone,  in 
consequence  of  which  their  boiling  point  and  the  temperature 
required  for  reduction  are  lower. 

J.  B.  Thompson  and  W.  White§  specify  mixing  dry  sodium 
carbonate  with  a  liquid  carbonaceous  material,  preferably  tar, 
driving  off  all  volatile  matter  in  iron  pots  at  a  low  heat,  and  then 
distilling  in  a  tubular  fire-clay  retort  connected  with  a  tightly- 
closed  receiver  containing  a  little  paraffin  oil  to  insure  a  non- 
oxidizing  atmosphere,  and  also  provided  with  a  small  escape  pipe 

*  Dingier,  1883,  p.  252. 

f  Handbuch  der  Angewandten  Chernie,  1830,  ii.  345. 

J  Dingier,  143,  343. 

§  English  Patent  8426,  June  11,  1887. 


166  ALUMINIUM. 

for  carbonic  oxide.  This  process  gave  great  prospects  of  suc- 
cess when  tried  in  the  laboratory,  but  on  a  manufacturing  scale  it 
failed  for  the  reason  (assigned  by  Mr.  Thompson)  that  the  sheet- 
iron  tray,  designed  to  keep  the  material  from  attacking  the  retort, 
absorbed  carbon  at  about  1000°  and  fused,  after  which  no  sodium 
was  produced,  since  the  material  took  up  silica  from  the  retort, 
absorbing  so  much  that  the  carbon  no  longer  decomposed  it. 

H.  S.  Blackmore,*  of  Mount  Vernon,  U.  S.  A.,  patents  the  fol- 
lowing process  of  obtaining  sodium  : — 

27£  parts  calcium  hydrate, 
31       "      ferric  oxide, 
31       "      dry  sodium  carbonate, 
10£     "      charcoal 

are  intimately  mixed  and  subjected  to  a  red  heat  for  20  minutes, 
afterwards  to  a  white  heat.  Caustic  soda  is  first  produced,  the 
carbon  reduces  the  ferric  oxide,  producing  iron,  which  in  its  turn 
reduces  the  caustic  soda  and  sodium  vapors  distil.  The  residue 
consists  of  ferric  oxide  and  lime,  and  is  slaked  and  used  over. 

O.  M.  Thowlessf  of  Newark,  N.  J.,  claims  to  place  a  retort  in 
a  furnace,  providing  it  on  one  side  with  an  arm  through  which 
carboniferous  material  can  be  supplied,  on  the  other  side  with  a 
similar  arm  (surrounded  by  flues),  into  which  caustic  soda  or 
sodium  carbonate  is  charged — a  valve  controlling  their  flow  into 
the  retort.  Outside  the  furnace  and  on  top  of  it  is  a  flat  conden- 
ser into  which  the  sodium  vapor  passes. 

G.  A.  Jar  vis  J  patents  the  replacement  of  the  iron  tubes  or 
crucibles  used  in  the  manufacture  of  sodium,  by  fire-clay  appara- 
tus lined  with  basic  material,  such  as  strongly  burnt  magnesia 
with  10  per  cent,  of  fluorspar. 

Castner's  Process  (1886). 

The  first  public  announcement  of  this  process  was  through  one 
of  the  New  York  daily  journals,§  and  as  the  tone  of  the  article  is 
above  that  of  the  usual  newspaper  reports,  and  the  expectations 
contained  in  it  have  been  subsequently  more  than  realized,  we 

*  English  Patent  15156,  Oct.  22,  1888. 
f  English  Patent  12486  (1887). 
t  English  Patent  4842,  March  31,  1888. 
§  New  York  World,  May  16,  1886. 


THE   MANUFACTURE   OF   SODIUM.  167 

cannot  better  introduce  a  description  of  this  process  than  by 
quoting  the  paragraph  referred  to  : — 

"When  sodium  was  reduced  in  price  to  $1.50  per  Ib.  it  was 
thought  to  have  touched  a  bottom  figure,  and  all  hope  of  making 
it  any  cheaper  seemed  fruitless.  This  cheapening  was  not  brought 
about  by  any  improved  or  new  process  of  reduction,  but  was 
owing  simply  to  the  fact  that  the  aluminium  industry  required 
sodium,  and  by  making  it  in  large  quantities  its  cost  does  not 
exceed  the  above-mentioned  price.  The  retail  price  is  now  $4.00 
per  Ib.  The  process  now  used  was  invented  by  Briinner,  in  1808, 
and  up  to  the  present  time  nothing  new  or  original  has  been 
patented  except  three  or  four  modifications  of  his  process  which 
have  been  adopted  to  meet  the  requirements  of  using  it  on  a  large 
scale.  Mr.  H.  Y.  Castner,  whose  laboratory  is  at  218  West 
Twentieth  Street,  New  York,  has  the  first  patent  ever  granted  on 
this  subject  in  the  United  States,  and  the  only  one  taken  out  in 
the  world  since  1808.  Owing  to  negotiations  being  carried  on, 
Mr.  Castner  having  filed  applications  for  patents  in  various 
foreign  countries,  but  not  having  the  patents  granted  there  yet, 
we  are  not  at  liberty  to  state  his  process  fully.  The  metal  is  re- 
duced and  distilled  in  large  iron  crucibles,  which  are  raised 
automatically  through  apertures  in  the  bottom  of  the  furnace, 
where  they  remain  until  the  reduction  is  completed  and  the 
sodium  distilled.  Then  the  crucible  is  lowered,  a  new  one  con- 
taining a  fresh  charge  is  substituted  and  raised  into  the  furnace, 
while  the  one  just  used  is  cleaned  and  made  ready  for  use  again. 
The  temperature  required  is  very  moderate,  the  sodium  distilling 
as  easy  as  zinc  does  when  being  reduced.  Whereas  by  previous 
processes  only  one-third  of  the  sodium  in  the  charge  is  obtained, 
Mr.  Castner  gets  nearly  all,  for  the  pots  are  nearly  entirely  empty 
when  withdrawn  from  the  furnace.  Thus  the  great  items  of 
saving  are  two  or  three  times  as  much  metal  extracted  from  a  given 
amount  of  salt,  and  cheap  cast-iron  crucibles  used  instead  of  ex- 
pensive wrought-iron  retorts.  Mr.  Castner  expects  to  produce 
sodium  at  25  cents  per  Ib.,  thus  solving  the  problem  of  cheap 
aluminium,  and  with  it  magnesium,  silicon,  and  boron,  all  of 
which  depend  on  sodium  for  their  manufacture.  Thus  the  pro- 
duction of  cheap  sodium  means  much  more  than  cheap  aluminium. 


168  ALUMINIUM. 

Mr.  Castner  is  well  known  in  New  York  as  a  chemist  of  good  stand- 
ing, and  has  associated  with  him  Mr.  J.  H.  Booth  and  Mr.  Henry 
Booth,  both  well  known  as  gentlemen  of  means  and  integrity." 

The  following  are  the  claims  which  Mr.  Castner  makes  in  his 
patent : — * 

1.  In  a  process  for  manufacturing  potassium  or  sodium,  per- 
forming the  reduction  by  diffusing  carbon  in  a  body  of  alkali  in 
a  state  of  fusion  at  moderate  temperatures. 

2.  Performing  the  reduction  by  means  of  the  carbide  of  a  metal 
or  its  equivalent. 

3.  Mechanically  combining  a  metal  and  carbon  to  increase  the 
weight  of  the  reducing  material,  and  then  mixing  this  product 
with  the  alkali  and  fusing  the  latter  whereby  the  reducing  material 
is  held  in  suspension  throughout  the  mass  of  fused  alkali. 

4.  Performing  the  deoxidation  by  the  carbide  of  a  metal  or  its 
equivalent. 

For  an  explanation  of  the  principles  made  use  of  in  the  above 
outlined  process  we  will  quote  from  a  lecture  delivered  by  Mr. 
Castner  at  the  Franklin  Institute,  Philadelphia,  October  12th, 
1886.  That  Institution  has  since  bestowed  on  Mr.  Castner  one 
of  its  gold  medals  as  a  recognition  of  the  benefit  to  science  ac- 
cruing from  his  invention. 

"  In  the  ordinary  sodium  process,  lime  is  added  to  the  reducing 
mixture  to  make  the  mass  refractory,  otherwise  the  alkali  would 
fuse  when  the  charge  is  highly  heated,  and  separate  from  the 
light,  infusible  carbon.  The  carbon  must  be  in  the  proportion 
to  the  sodium  carbonate  as  four  is  to  nine,  as  is  found  needful 
in  practice,  so  as  to  assure  each  particle  of  soda  in  the  refractory 
charge  having  an  excess  of  carbon  directly  adjacent  or  in  actual 
contact.  Notwithstanding  the  well-known  fact  that  sodium  is 
reduced  from  its  oxide  at  a  degree  of  heat  but  slightly  exceeding 
the  reducing  point  of  zinc  oxide,  the  heat  necessary  to  accomplish 
reduction  by  this  process  and  to  obtain  even  one-third  of  the 
metal  in  the  charge,  closely  approaches  the  melting  point  of 
wrought  iron. 

"  In  my  process,  the  reducing  substance,  owing  to  its  composi- 
tion and  gravity,  remains  below  the  surface  of  the  molten  salt, 

*  U.  S.  Pat.  No.  342897,  June  1,  188(5.      Hamilton  Y.  Castner,  New  York. 


THE   MANUFACTURE   OF   SODIUM.  169 

and  is,  therefore,  in  direct  contact  with  the  fused  alkali.  The 
metallic  coke  of  iron  and  carbon  contains  about  30  per  cent, 
carbon  and  70  per  cent,  iron,  equivalent  to  the  formula  FeC2.  I 
prefer  to  use  caustic  soda,  on  account  of  its  fusibility,  and  mix 
with  it  such  quantity  of  so-called  '  carbide'  that  the  carbon  con- 
tained in  the  mixture  shall  not  be  in  excess  of  the  amount  theo- 
retically required  by  the  following  reaction : — 

3NaOH  +  FeC2=  3Na  +  Fe  +  CO  4-  CO2  +  3H ; 

or,  to  every  100  Ibs.  of  pure  caustic  soda,  75  Ibs.  of  '  carbide/ 
containing  about  22  Ibs.  of  carbon. 

"  The  necessary  cover  for  the  crucible  is  fixed  stationary  in 
each  chamber,  and  from  this  cover  a  tube  projects  into  the  con- 
denser outside  the  furnace.  The  edges  of  the  cover  are  convex, 
those  of  the  crucible  concave,  so  that  when  the  crucible  is  raised 
into  position  and  held  there  the  tight  joint,  thus  made  prevents  all 
leaking  of  gas  or  vapor.  Gas  is  used  as  fuel,  and  the  reduction 
begins  towards  1000°  C.  As  the  charge  is  fused,  the  alkali  and 
reducing  material  are  in  direct  contact,  and  this  fact,  together 
with  the  aid  rendered  the  carbon  by  the  fine  iron,  in  withdrawing 
oxygen  from  the  soda,  explains  why  the  reduction  is  accom- 
plished at  a  moderate  temperature.  Furthermore,  by  reducing 
from  a  fused  mass,  in  which  the  reducing  agent  remains  in  sus- 
pension, the  operation  can  be  carried  on  in  crucibles  of  large 
diameter,  the  reduction  taking  place  at  the  edges  of  the  mass, 
where  the  heat  is  greatest,  the  charge  flowing  thereto  from  the 
centre  to  take  the  place  of  that  reduced. 

"  I  am  enabled  to  obtain  fully  90  per  cent,  of  the  metal  in  the 
charge,  instead  of  30  per  cent,  as  formerly.  The  crucibles,  after 
treatment,  contain  a  little  carbonate  of  soda,  and  all  the  iron  of 
the  '  carbide'  still  in  a  fine  state  of  division,  together  with  a  small 
percentage  of  carbon.  These  residues  are  treated  with  warm 
water,  the  solution  evaporated  to  recover  the  carbonate  of  soda, 
while  the  fine  iron  is  dried,  and  used  over  again  for  ( carbide.7  r' 

Mr.  Castner  having  demonstrated  in  his  New  York  laboratory 
the  success  of  his  process,  went  to  England,  and  for  several 
months  during  the  winter  of  1886-7  was  engaged  in  building 
and  working  a  large  sodium  furnace.  This  was  successfully  car- 


170  ALUMINIUM. 

ried  out  near  London,  the  inventor  being  assisted  by  Mr.  J.  Mac- 
Tear,  F.C.S.,  who,  in  March,  1887,  read  a  description  of  this 
furnace  and  the  results  obtained  before  the  Society  of  Chemical 
Industry.  During  the  working  of  this  furnace  it  was  inspected 
by  many  chemical  and  metallurgical  authorities,  who  were  com- 
pletely satisfied  as  to  its  success.  As  the  furnace  now  used  differs 
in  a  few  details  from  the  one  j  ust  referred  to,  it  may  be  well  to 
extract  the  essential  particulars  from  Mr.  MacTear's  paper — on 
the  ground  that  the  importance  of  this  invention  justifies  a  com- 
plete discussion  of  its  development : — 

"  Since  Mr.  Castner's  paper  upon  his  process,  which  was  read 
before  the  Franklin  Institute  of  Philadelphia,  October  12th, 
1886,  several  slight  changes  in  the  mode  of  carrying  on  this 
process  have  been  made.  These  have  been  brought  about  by 
the  experience  gained  from  the  actual  working  of  the  process 
upon  a  commercially  large  scale. 

"  The  reactions  by  which  the  sodium  is  produced  are  some- 
what difficult  to  describe,  as  they  vary  somewhat  according  to 
the  mixture  of  materials  and  temperature  employed  in  the  reduc- 
tion. The  mixture  and  temperature  which  it  is  now  preferred  to 
use  is  represented  by  the  reaction  : — 

6NaHO  +  FeC8  -  2Na2CO3  +  6H  -f  Fe  +  21Na. 

"  In  place  of  using  an  actual  chemical  compound  of  iron  and 
carbon,  as  expressed  by  the  above  reaction,  a  substitute  or  equiva- 
lent is  prepared  as  follows :  To  a  given  quantity  of  melted  pitch 
is  added  a  definite  proportion  of  iron  in  a  fine  state  of  division. 
The  mixture  is  cooled,  broken  up  into  lumps,  and  cooked  in  large 
crucibles,  giving  a  metallic  coke  consisting  of  carbon  and  iron, 
the  proportions  of  each  depending  upon  the  relative  quantities  of 
pitch  and  iron  used.  This  metallic  coke,  after  being  finely  ground, 
provides  a  substance  having  the  iron  and  carbon  in  a  like  propor- 
tion to  an  iron  carbide,  and  from  which  neither  the  iron  nor  car- 
bon can  be  separated  by  mechanical  means.  The  fine  iron  is 
conveniently  prepared  by  passing  carbonic  oxide  and  hydrogen 
in  a  heated  state,  as  obtained  from  an  ordinary  gas  producer,  over 
a  mass  of  oxide  of  iron  commercially  known  as  i  purple  ores/ 
heated  to  a  temperature  of  about  500°  C. 


THE   MANUFACTURE   OF   SODIUM.  171 

"  In  producing  sodium,  caustic  soda  of  the  highest  obtainable 
strength  is  used,  and  there  is  mixed  with  it  a  weighed  quantity 
of  the  so-called  '  carbide/  sufficient  to  furnish  the  proper  amount 
of  carbon  to  carry  out  the  reaction  indicated  above.  The  cruci- 
bles in  which  this  mixture  is  treated  are  made  of  cast-steel,  and 
are  capable  of  containing  a  charge  of  15  Ibs.  of  caustic  soda, 
together  with  the  proper  proportion  of  the  i  carbide/ 

"  After  charging  a  crucible  with  the  above  mixture,  it  is  placed 
in  a  small  furnace  where  it  is  kept  at  a  low  heat  for  about  thirty 
minutes,  during  which  time  the  mass  fuses,  boils  violently,  and  a 
large  part  of  the  hydrogen  is  expelled  by  the  combined  action  of 
the  iron  and  carbon,  the  '  carbide/  owing  to  its  gravity,  remaining 
in  suspension  throughout  the  fused  soda.  At  the  end  of  the  time 
stated,  the  contents  of  the  crucible  have  subsided  to  a  quiet 
fusion.  The  crucible  is  then  lifted  by  a  pair  of  tongs  on  wheels 
and  placed  upon  the  platform  of  the  elevating  gear,  as  shown  in 
the  drawing,  and  raised  to  its  position  in  the  heating  chamber  of 
the  main  distilling  furnace.  The  cover  which  remains  stationary 
in  the  furnace  has  a  convex  edge,  while  the  crucible  has  a  groove 
round  the  edge  into  which  the  edge  of  the  cover  fits.  A  little 
powdered  lime  is  placed  in  the  crucible  groove  just  before  it  is 
raised,  so  that  when  the  edges  of  the  cover  and  crucible  come 
together  they  form  a  tight  joint,  and  at  the  same  time  will  allow 
the  crucible  to  be  lowered  easily  from  the  chamber  when  the 
operation  is  finished,  to  give  place  to  another  containing  a  fresh 
charge.  From  the  cover  projects  a  slanting  tube  (see  Fig.  17), 
connected  with  the  condenser.  The  condenser  is  provided  with  a 
small  opening  at  the  further  end  to  allow  the  escape  of  hydrogen, 
and  has  also  a  rod  fixed  (as  shown),  by  means  of  which  any 
obstruction  which  may  form  in  the  tube  during  distillation,  may 
be  removed.  After  raising  a  crucible  in  its  place  in  the  furnace, 
the  hydrogen  escaping  from  the  condenser  is  lighted,  and  serves 
to  show  by  the  size  of  the  flame  how  the  operation  is  progressing 
in  the  crucible,  the  sodium  actually  distilling  soon  after  the  cru- 
cible is  in  its  place.  The  temperature  of  the  reduction  and  dis- 
tillation has  been  found  to  be  about  823°  C.  The  gas  coming 
off  during  the  first  part  of  the  distillation  has  been  analyzed 
and  found  to  consist  of  pure  hydrogen.  An  analysis  of  the  gas 


172  ALUMINIUM. 

disengaged  when  the  operation  was  almost  completed,  gave  as 
a  result,  hydrogen  95  per  cent.,  carbonic  oxide  5  per  cent.     It 

Fig.  17. 


has  been  found  advisable  to  use  a  little  more  '  carbide'  than  the 
reaction  absolutely  requires,  and  this  accounts  for  the  presence 
of  the  small  quantity  of  carbonic  oxide  in  the  expelled  gas,  the 
free  carbon  acting  upon  the  carbonate  formed  by  the  reaction,  thus 
giving  off  carbonic  oxide  and  leaving  a  very  small  percentage  of 
the  residue  in  the  form  of  peroxide  of  sodium.  This  small  amount 
of  carbonic  oxide  rarely  combines  with  any  of  the  sodium  in  the 
tube,  and  so  the  metal  obtained  in  the  condensers  is  pure,  and  the 
tubes  never  become  choked  with  the  black  compound.  In  the 
preparation  of  potassium  a  little  less  '  carbide'  is  used  than  the 
reaction  requires,  thus  no  carbonic  oxide  is  given  off,  and  all 
danger  attached  to  the  making  of  potassium  is  removed.  After 
the  reduction  and  distillation  the  crucible  is  lowered  from  the 
furnace  and  the  contents  poured  out,  leaving  the  crucible  ready 
to  be  recharged.  The  average  analyses  of  the  residues  show  their 
composition  to  be  as  follows: — 


THE   MANUFACTURE   OF   SODIUM.  173 

Carbonate  of  soda       ......  77  per  cent. 

Peroxide  of  sodium     .         .         .         .         .  2       " 

Carbon .       2        " 

Iron  19        " 

"  The  average  weight  of  these  residues  from  operating  upon 
charges  of  15  Ibs.  caustic  soda  and  5J  Ibs.  of  carbide  is  16  Ibs. 
These  residues  are  treated  either  to  produce  pure  crystallized 
carbonate  of  soda  or  caustic  soda,  and  the  iron  is  recovered  and 
used  again  with  pitch  in  the  formation  of  the  '  carbide/  From 
this  residue  weighing  16  Ibs.,  is  obtained  13  Ibs.  of  anhydrous 
carbonate  of  soda,  equivalent  to  9.4  Ibs.  caustic  soda  of  76  per 
cent. 

"  Operating  upon  charges  as  above  mentioned  the  yield  has 
been — 

Sodium,  actual  .       ,?         .     2.50  Ibs.     Theory      2.85  Ibs. 
Soda  carbonate,  actual        .  13.00  Ibs.          "         13.25  Ibs. 

"  The  average  time  of  distillation  in  the  large  furnace  has  been 
1  hour  30  minutes,  and  as  the  furnace  is  arranged  for  three  cru- 
cibles, 45  Ibs.  of  caustic  soda  are  treated  every  90  minutes,  pro- 
ducing 7  J  Ibs.  of  sodium  and  39  Ibs.  of  carbonate  of  soda.     The 
furnace  is  capable  of  treating  720  Ibs.  of  caustic  soda  daily, 
giving  a  yield  in  24  hours  of  120  Ibs.  of  sodium  and  624  Ibs. 
of  anhydrous  carbonate  of  soda.     The  furnace  is  heated  by  gas 
which  is  supplied  by  a  Wilson  Gas  Producer,  consuming  1  cwt. 
of  fuel  per  hour.     The  small  furnace  in  which  the  crucibles  are 
first  heated  requires  about  J  cwt.  per  hour.     The  following  esti- 
mate of  cost,  etc.,  is  given  from  the  actual  running  of  the  furnace 
working  with  the  above  charges  for  24  hours  : — 

£    *.     d. 

720  Ibs.  of  caustic  soda  @  £11  per  ton     *      .  V        .     3     10     10 
150  Ibs.  of  "  carbide"  @  \d.  per  Ib.          .         .         .064 

Labor        ...         .         .         .         *      .  ^        .     1       0       0 

Fuel          ....         .         .         .         .         .     0     17       0 

Re-converting  624  Ibs.  of  carbonate  into  caustic,  at 
a  cost  of  about  £5  per  ton  on  the  caustic  pro- 
duced, say  .  .  ...  .  .  .100 

Total        .        ...     6     14      2 
Deducting  value  of  475  Ibs.  of  caustic  recovered     268 


Cost  of  120  Ibs.  of  sodium  ...         .£4 

Cost  per  pound  85^. 


174  ALUMINIUM. 

"  Regarding  the  item  of  cost  relating  to  the  damage  caused  to 
the  crucibles  by  the  heat,  this  question  has  been  very  carefully 
gone  into,  some  of  the  crucibles  have  been  used  upwards  of  fifty 
times,  and  from  present  indications  of  their  condition  there  is  no 
doubt  that  they  can  continue  to  be  used  at  least  150  times  more 
before  they  become  unfit  for  further  use.  In  considering  200 
operations  to  be  the  life  of  a  crucible,  the  item  of  damage  or 
wear  and  tear  amounts  to  less  than  lc/.  per  Ib.  on  the  sodium 
produced,  and  if  we  take  the  furnace  tear  and  wear  at  the  same 
rate  of  Id.  per  Ib.,  we  will  see  that  the  tear  and  wear  of  plant 
is  only  one-twelfth  of  that  incurred  in  the  ordinary  process.  It 
is  upon  these  facts  that  Mr.  Castner  bases  his  claim  to  be  able 
to  produce  sodium  by  his  process  upon  the  large  scale,  at  a  cost 
of  less  than  Is.  per  Ib.  The  advantages  of  this  process  will  be 
apparent  to  any  one  at  all  familiar  with  the  manufacture  of  these 
metals  as  conducted  heretofore.  The  first  and  most  important 
end  gained  is  their  cheap  production,  and  this  is  owing  chiefly 
to  the  low  heat  at  which  the  metals  are  produced,  the  quick- 
ness of  the  operation,  non-clogging  of  the  conveying  tubes,  and 
a  very  small  waste  of  materials.  The  process  furthermore  admits 
of  being  carried  on  upon  a  very  large  scale,  in  fact  it  is  intended 
ultimately  to  increase  the  size  of  the  crucible  so  as  to  make  the 
charges  consist  of  50  Ibs.  of  caustic  soda.  Crucibles  of  cast  iron 
have  been  found  quite  suitable,  and  it  is  intended  in  future  to  use 
crucibles  made  of  this  material  in  place  of  the  more  expensive 
steel." 

Immediately  on  the  demonstration  of  this  success,  a  company 
was  formed  to  unite  Mr.  Castner's  sodium  process  with  Mr. 
Webster's  improvements  in  the  production  of  aluminium  chlor- 
ide. The  Aluminium  Co.,  Ltd.,  first  appeared  before  the  public 
in  June,  1887,  and  at  the  first  meeting  in  the  following  September 
it  was  decided  to  build  works  at  once.  These  were  begun  at 
Oldbury,  near  Birmingham,  and  were  in  working  operation  by 
the  end  of  July,  1888.  The  furnaces  here  erected  are  larger  than 
the  one  just  described,  and  altogether  have  a  producing  capacity 
of  nearly  a  ton  of  sodium  a  day.  The  following  details  respecting 
this  latest  plant  and  its  working  are  taken  mostly  from  an  address 
delivered  before  the  Society  of  Arts,  March  13,  1889,  by  Mr. 


THE   MANUFACTURE   OF   SODIUM.  175 

William  Anderson,  and  from  a  discourse  at  the  Royal  Institu- 
tion, May  3,  1889,  by  Sir  Henry  Roscoe,  president  of  the 
company. 

There  are  four  large  sodium  furnaces,  each  holding  five  pots  or 
crucibles  and  heated  by  gas,  applied  on  the  regenerative  prin- 
ciple. A  platform  about  five  feet  above  the  floor  allows  the 
workmen  to  attend  to  the  condensers,  while  the  lifts  on  which 
the  pots  are  placed  sink  level  with  the  floor.  The  crucibles  used 
are  egg-shaped,  about  1 8  inches  diameter  at  their  widest  part 
and  24  inches  high  ;  when  joined  to  the  cover  the  whole  apparatus 
is  about  3  feet  in  height.  The  covers  have  vertical  pipes  passing 
through  the  top  of  the  furnace,  forming  a  passage  for  the  intro- 
duction of  part  of  the  charge,  and  also  a  lateral  pipe  connecting 
with  the  condenser.  The  whole  cover  is  fixed  immovably  to 
the  roof  of  the  furnace  and  is  protected  by  brickwork  from  ex- 
treme heat ;  but  it  can  easily  be  removed  when  necessary.  The 
natural  expansion  of  the  vessels  is  accommodated  by  the  water 
pressure  in  the  hydraulic  lifts  on  which  the  pots  stand.  When 
the  lift  is  lowered  and  sinks  with  the  lower  part  of  the  crucible 
to  the  floor  level,  a  large  pair  of  tongs  mounted  on  wheels  is  run 
up,  and  catching  hold  of  the  crucible  by  two  projections  on  its 
sides  it  is  carried  away  by  two  men  to  the  dumping  pits,  on  the 
edge  of  which  it  is  turned  on  its  side,  the  liquid  carbonate  of  soda 
and  finely  divided  iron  which  form  the  residue  are  turned  out, 
and  the  inside  is  scraped  clean  from  the  opposite  side  of  the  pit, 
under  the  protection  of  iron  shields.  When  clean  inside  and  out, 
it  is  lifted  again  by  the  truck  and  carried  back  to  the  furnace,  re- 
ceiving a  fresh  charge  on  its  way.  It  is  then  put  on  the  platform 
and  lifted  into  place,  having  still  retained  a  good  red  heat. 
It  takes  only  1J  to  2  minutes  to  remove  and  empty  a  crucible, 
and  only  6  to  8  minutes  to  draw,  empty,  recharge,  and  replace 
the  five  crucibles  in  each  furnace.  The  time  occupied  in  reducing 
a  charge  is  one  hour  and  ten  minutes.  It  is  thus  seen  that  one 
bank  of  crucibles  yields  500  pounds  of  sodium  in  twenty-four 
hours,  the  battery  of  four  furnaces  produces  about  a  ton  in  that 
time. 

The  shape  of  the  condenser  has  been  altogether  changed.  In- 
stead of  the  flat  form  used  on  the  furnace  at  London  (see  Fig.  17), 


176  ALUMINIUM. 

which  resembled  the  condenser  used  in  the  Deville  process,  a 
peculiar  pattern  is  used  which  is  quite  different.  It  consists  in 
a  tube-shaped  cast-iron  vessel  5  inches  in  diameter,  nearly  3  feet 
long  over  all,  and  having  a  slight  bend  upwards  at  a  point  about 
20  inches  from  the  end.  At  this  bend  is  a  small  opening  in  the 
bottom,  which  can  be  kept  closed  by  a  rod  dropping  into  it ;  this 
rod,  passing  through  a  tight-fitting  hole  above,  can  be  raised  or 
lowered  from  outside.  Thus  the  sodium  can  either  run  out  con- 
tinually into  small  pots  placed  beneath  the  opening  or  can  be  al- 
lowed to  collect  in  the  condenser  until  several  pounds  are  present, 
then  a  small  potful  run  out  at  once,  by  simply  lifting  the  iron 
rod.  The  outer  end  of  the  condenser  is  provided  with  a  lid, 
hinged  above,  which  can  be  thrown  back  out  of  the  way  when 
required.  This  lid  also  contains  a  small  peep-hole  covered  with 
mica.  In  the  top  of  the  condenser  just  before  the  end  is  a  small 
hole  through  'which  the  hydrogen  and  carbonic  oxide  gases  es- 
cape when  the  end  is  closed,  burning  with  the  yellow  sodium 
flame.  The  bend  in  the  condenser  is  not  acute  enough  to  prevent 
a  bar  being  thrust  through  the  end  right  into  the  outlet  tube  pro- 
jecting from  the  furnace,  thus  allowing  the  whole  passage  to  be 
cleaned  out  should  it  become  choked  up.  Previous  to  drawing 
the  crucibles  from  the  furnace  for  the  purpose  of  emptying  them 
and  recharging,  the  small  pots  containing  the  metal  distilled  from 
one  charge  are  removed  and  empty  ones  put  in  their  place. 
Those  removed  each  contain  on  an  average  about  6  Ibs.  of  sodium, 
or  30  Ibs.  from  the  whole  furnace.  When  sufficiently  cool,  petro- 
leum is  poured  on  top  of  the  metal  in  the  pots,  and  they  are 
wheeled  on  a  truck  to  the  sodium  casting  shop,  where  the  sodium 
is  melted  in  large  pots  heated  by  oil  baths  and  cast  either  into 
large  bars  ready  to  be  used  for  making  aluminium  or  into  smaller 
sticks  to  be  sold.  The  sodium  is  preserved  under  an  oil  such  as 
petroleum,  which  does  not  contain  oxygen  in  its  composition,  and 
the  greatest  care  is  taken  to  protect  it  from  water. 

Special  care  is  taken  to  keep  the  temperature  of  the  furnace  at 
about  1000°  C.,  and  the  gas  and  air-valves  are  carefully  regulated 
so  as  to  maintain  as  even  a  temperature  as  possible.  The  covers 
remain  in  the  furnace  from  Sunday  night  to  Saturday  afternoon, 
and  the  crucibles  are  kept  in  use  till  worn  out,  when  new  ones, 


THE   MANUFACTURE   OF   SODIUM.  177 

previously  heated  red-hot,  are  substituted  without  interrupting 
the  general  running  of  the  furnace.  These  bottom  halves  of  the 
crucibles  are  the  only  part  of  the  plant  liable  to  exceptional  wear 
and  tear,  and  their  durability  is  found  to  depend  very  much  on 
the  soundness  of  the  casting,  because  any  pores  or  defects  are 
rapidly  eaten  into  and  the  pot  destroyed.  The  average  duration 
of  each  crucible  is  now  750  Ibs.  of  sodium,  or  125  charges. 

Apropos  of  the  reaction  involved  in  the  reduction,  it  has  prob- 
ably been  observed  that  Mr.  MacTear  proposes  a  different  form- 
ula from  that  suggested  by  Mr.  Castner.  Mr.  Weldon  remarked 
that  when  a- mixture  of  sodium  carbonate  and  carbon  was  heated 
the  carbon  did  not  directly  reduce  the  soda,  but  at  a  high  tem- 
perature the  mixture  gives  off  vapors  of  oxide  of  sodium  (Na2O) 
part  of  which  dissociates  into  free  oxygen  and  sodium  vapor ;  as 
soon  as  this  dissociation  takes  place  the  carbon  ,takes  up  the 
oxygen,  forming  carbonic  oxide,  and  thus,  by  preventing  the  re- 
combination of  the  sodium  and  oxygen,  leaves  free  sodium  vapors. 
Dr.  Kosman,  speaking  in  "Stahl  und  Eisen,"  January,  1889, 
on  Castner's  process,  gives  the  following  explanation  of  the  reac- 
tions taking  place : — 

Ten  kilos  of  caustic  soda  and  5  kilos  of  carbide  (containing 
1.5  kilos  of  carbon)  give  the  following  reaction  : — 

4NaOH  +  FeC2=  Na2CO3  +  Fe  +  4H  -f  CO  +  2Na, 
and  half  the  sodium  in  the  mixture  is  obtained. 

Ten  kilos  of  caustic  soda  and  10  kilos  of  carbide  (containing 
3  kilos  of  carbon)  give  this  reaction — 

2NaOH  +  FeC2= NaCO  +  Fe  +  2H  +  CO  +  Na, 
and  half  the  sodium  in  the  mixture  is  again  obtained. 

If  20  kilos  of  caustic  soda  and  15  kilos  of  carbide  are  mixed, 
both  the  above  reactions  take  place,  but  if  the  ignition  is  con- 
tinued, the  sodium  carboxyd  (NaCO)  reacts  on  the  sodium  car- 
bonate according  to  the  reaction — 

Na2CO3  +  NaCO  «  3Na  +  2CO2, 
and  the  entire  reaction  may  be  represented  by 

3NaOH  +  FeC2=  3Na  -f  Fe  +  3H  +  CO  +  CO2, 
and  all  the  sodium  in  the  mixture  is  obtained. 

This  is  the  reaction  first  proposed  by  Mr.  Castner  (see  p.  169), 
12 


1 78  ALUMINIUM. 

and  the  proportions  indicated  by  it  gave  him  the  largest  return 
of  sodium.  Mr.  MacTear,  however,  states  that  the  reaction 
which  takes  place  is  conditioned  largely  by  the  temperature,  and 
that  at  1000°  C.  it  is  probably  to  be  represented  by 

6NaOH  +  FeC2~  2Na*CO»  +  6H  +  Fe  +  2Na, 
which  is  essentially  the  same  as  that  given  by  Sir  Henry  Roscoe 
in  his  discourse,  viz  : — 

3NaOH  +  C-  Na2C03  +  3H  +  Na. 

This  reaction  would  require  18f  Ibs.  of  carbide  to  50  Ibs.  of 
caustic  soda,  and  since  the  sodium  carbonate  is  easily  converted 
back  into  caustic  by  treatment  with  lime,  the  production  of  so 
much  carbonate  is  offset  by  the  ease  with  which  the  reaction  takes 
place,  and  the  added  advantage  that  the  gas  evolved  with  the 
sodium  is  solely  hydrogen,  thus  allowing  the  reduction  to  proceed 
in  an  atmosphere  of  that  gas,  and  reducing  the  production  of  the 
usual  deleterious  sodium  carbides  to  a  minimum. 

A  further  discussion  of  this  subject  will  come  up  in  consider- 
ing Netto's  process. 

Netto's  Process  (1887). 

Dr.  Curt  Netto,  of  Dresden,  has  taken  out  patents  in  several 
European  countries,*  which  have  been  transferred  to  and  are  pre- 
sumably being  operated  by  the  Alliance  Aluminium  Company, 
of  London  (see  p.  38).  The  process  is  continuous,  and  is  based 
on  the  partial  reduction  of  caustic  soda  by  carbon.  Dr.  Netto 
observes  that  carbon  will  reduce  caustic  soda  at  first  at  a  red  heat, 
but  a  white  heat  is  necessary  to  finish  the  reduction,  the  explana- 
tion being  that  the  reaction  is  at  first — 

4NaOH  +  C = Na2CO3  +  2H2  4-  CO  +  Na2, 

and  that  the  carbonate  is  only  reduced  at  a  white  heat.  To  avoid 
any  high  temperature,  the  first  reaction  only  is  made  use  of,  the 
carbonate  being  removed  and  fresh  caustic  supplied  continuously, 
and  without  interrupting  the  operation  or  admitting  air  into  the 
retort  in  which  the  reduction  takes  place. 

A  vertical  cast-iron  retort,  protected  by  fire-clay  coating,  is 

*  German  patent  (D.  R.  P.)  45105  ;  English  patent,  October  26,  1887,  No. 
14602. 


THE   MANUFACTURE   OF   SODIUM. 


179 


surrounded  by  flues.  The  flame  after  heating  the  retort  passes 
under  an  iron  pot  in  which  the  caustic  soda  is  kept  melted,  and 
situated  just  above  the  top  of  the  retort.  This  pot  has  an  outlet 
tube  controlled  by  a  stop-cock,  by  which  the  caustic  may  be  dis- 
charged into  a  funnel  with  syphon-shaped  stem  fastened  into  the 
top  of  the  retort.  There  is  also  a  syphon-shaped  outlet  at  the  bot- 
tom of  the  retort,  through  which  the  molten  sodium  carbonate  and 
bits  of  carbon  pass.  A  hole  with  tight  lid  in  the  upper  cover  is 
provided  for  charging  charcoal.  A  tube  passes  out  just  beneath 
the  upper  cover,  connecting  with  a  large  condenser  of  the  shape 
used  by  Deville  (see  Fig.  18).  In  operating,  the  retort  is  heated 

Fig.  18. 


to  bright  redness,  filled  one-third  with  best  wood  charcoal,  and 
then  molten  caustic  soda  tapped  from  the  melting  pot  into  the 
funnel,  the  feed  being  so  regulated  that  the  funnel  is  kept  full  and 
the  retort  closed.  The  lower  opening  is  kept  closed  until  enough 


180  ALUMINIUM. 

sodium  carbonate  has  accumulated  to  lock  the  syphon  passage  air 
tight.  When  after  several  hours'  working  the  charcoal  is  almost 
all  used  up,  the  supply  of  caustic  soda  is  shut  off  for  a  time  and 
the  retort  recharged  through  the  opening  in  the  upper  lid,  when 
the  operation  goes  on  as  before.  The  sodium  carbonate  produced 
is  easily  purified  from  carbon  by  solution.  Since  sodium  vapor 
at  a  high  temperature  is  very  corrosive,  all  rivets  and  screw  joints 
must  be  avoided  in  making  the  retort.  On  this  account,  the  out- 
let tubes  should  be  cast  in  one  piece  with  the  retort. 

The  process  of  O.  M.  Thowless,  Newark,  IS".  J.,*  is  essentially 
identical  with  Netto's  process. 

REDUCTION  OF  SODIUM  COMPOUNDS  BY  ELECTRICITY. 

The  decomposition  of  fused  sodium  chloride  by  the  electric 
current  seems  to  promise  the  economic  production  of  sodium,  for 
not  only  is  this  metal  formed  but  chlorine  is  obtained  as  a  by- 
product, its  value  reducing  very  much  the  cost  of  the  operation. 

P.  Jablochoff  has  devised  the  following  apparatus  for  decom- 
posing sodium  or  potassium  chlorides. f  (Fig.  19.) 

The  arrangement  is  easily  understood.  The  salt  to  be  decom- 
posed is  fed  in  by  the  funnel  into  the  kettle  heated  by  a  fire 
beneath.  The  positive  pole  evolves  chlorine  gas,  and  the  negative 
pole  evolves  vapor  of  the  metal,  for,  as  the  salt  is  melted,  the  heat 
is  sufficient  to  vaporize  the  metal  liberated.  The  gas  escapes 
through  one  tube  and  the  metallic  vapor  by  the  other.  The  vapor 
is  led  into  a  condenser  and  solidified. 

Prof.  A.  J.  Rogers,  of  Milwaukee,  Wis.,  has  made  a  number 
of  attempts  to  reduce  sodium  compounds  electrolytically,  using  as 
a  cathode  a  bath  of  molten  lead  and  producing  an  alloy  of  lead 
and  sodium  which  he  makes  use  of  for  the  reduction  of  aluminium 
compounds.  Although  these  attempts  are  hardly  past  the  experi- 
mental stage,  yet  the  record  of  the  results  obtained  may  very 
probably  be  interesting  and  valuable  to  other  investigators  in 
this  line. 

Prof.  Rogers  reasons  that  from  the  known  heat  of  combination 

*  U.  S.  Patent,  Nos.  380775,  380776,  April  4,  1888.  f  Mierzinski. 


THE   MANUFACTURE   OF   SODIUM. 


181 


of  sodium  and  chlorine  (4247  calories  per  kilo  of  sodium)  there 
is  enough  potential  energy  in  a  pound  of  coal  to  separate  nearly 
two  pounds  of  sodium,  if  any  mode  of  applying  the  combustion 
of  the  coal  to  this  end  without  loss  could  be  devised.  If,  however, 

Fig.|19. 


this  energy  is  converted  into  mechanical  work,  this  again  into 
electrical  energy,  and  this  latter  used  to  decompose  sodium  chlor- 
ide, we  can  easily  compute  the  amount  of  coal  to  be  used  in  a 
steam  boiler  to  produce  a  given  amount  of  sodium  by  electrolysis. 
Now,  if  the  electric  current  could  be  applied  without  loss  in  de- 
composing sodium  chloride,  1  electric  horse-power  (746  Watts) 
would  produce  about  8  Ibs.  of  sodium  in  24  hours.  But  as  in 
practice  one  mechanical  horse-power  applied  to  a  dynamo  yields 
only  80  or  90  per  cent,  of  an  electric  horse-power,  and  as  about 
4  Ibs.  of  coal  are  used  per  indicated  horse-power  per  hour,  from 
105  to  120  Ibs.  of  coal  would  be  required  per  day  to  produce  this 
result,  or  about  15  Ibs.  per  Ib.  of  sodium.  Since,  however,  there 
is  a  transfer  resistance  in  the  passage  of  the  electric  current  through 
the  molten  electrolyte,  more  than  this  will  be  required,  in  propor- 
tion to  the  amount  of  current  thus  absorbed. 


182  ALUMINIUM. 

The  temperature  of  fusion  of  sodium  chloride  is  given  by  Car- 
nelly  as  776°  C.,  but  Prof.  Rogers  remarks  that  the  fusing  point 
may  be  lowered  considerably  by  the  presence  of  other  salts  ;  for 
instance,  it  melts  about  200°  lower  if  a  small  amount  of  calcium 
chloride  or  potassium  chloride  is  present.  We  will  quote  the 
results  of  some  experiments  as  given  by  Prof.  Rogers.* 

"  The  following  results  were  obtained  among  many  others  by 
using  a  Grove  battery,  a  Battersea  crucible  to  hold  the  sodium 
chloride,  a  carbon  anode  and  an  iron  cathode  terminating  in  a 
tube  of  lime  placed  in  the  melted  salt.  As  soon  as  metallic 
sodium  escaped  and  burnt  at  the  surface  of  the  liquid  the  current 
was  stopped.  A  little  sodium  was  oxidized  but  a  considerable 
amount  was  found  in  the  tube  in  metallic  state.  In  six  experi- 
ments the  amount  of  sodium  obtained  was  from  50  to  85  per 
cent,  of  the  theoretical  amount,  averaging  65  per  cent.  It  thus 
seemed  that,  with  suitable  apparatus,  from  5  to  6  Ibs.  of  sodium 
could  be  obtained  in  24  hours  per  electric  horse-power.  Thus, 
if  there  were  no  practical  difficulties  in  the  construction  of  the 
crucibles  and  other  apparatus  involved,  nor  in  working  continu- 
ously on  a  large  scale,  the  metal  could  be  obtained  at  small  cost. 
Various  forms  of  crucibles  were  used  and  attempts  made  to  distil 
the  metal  when  formed  at  the  negative  electrode  (sodium  volatili- 
zing at  about  900°C.),  but  the  sodium  vapor  carries  with  it  a  large 
amount  of  sodium  chloride  as  vapor,  and  the  distillation  is 
attended  with  difficulty. 

"  During  the  last  three  years  I  have  experimented  on  the  re- 
duction of  sodium  chloride  using  molten  negative  electrodes  and 
especially  lead.  Lead,  tin,  zinc,  cadmium  and  antimony  all  readily 
alloy  with  sodium,  a  large  part  of  which  can  be  recovered  from 
the  alloys  by  distillation  in  an  iron  crucible.  They  can  be  heated 
to  a  higher  temperature  than  pure  sodium  in  acid  crucibles  with- 
out the  sodium  attacking  the  crucible.  In  the  following  experi- 
ments a  dynamo  machine  was  used  to  supply  the  current. 

"Experiment  1.  A  current  averaging  72  amperes  and  33  volts 
was  passed  through  molten  sodium  chloride  contained  in  two 
crucibles  arranged  in  series,  for  two  hours.  Each  contained  30 

*  Proceedings  of  the  Wisconsin  Natural  History  Society,  April,  1889. 


REDUCTION   THEORETICALLY   CONSIDERED.  183 

Ibs.  of  salt ;  in  the  first  was  put  104  grammes  of  tin,  in  the  second 
470  grammes  of  lead,  each  serving  as  cathode  and  connection 
being  made  through  the  bottom  of  the  crucible.  A  carbon  anode 
passed  through  the  cover  and  extended  to  within  three  inches  of 
the  molten  cathode.  The  crucible  containing  the  tin  was  nearer 
the  fire  and  consequently  hotter,  and  had  an  average  potential 
across  the  electrodes  of  12  volts,  while  that  containing  the  lead 
cathode  was  21  volts.  When  at  the  end  of  two  hours  the  carbons 
were  removed  and  the  crucibles  cooled  and  broken  open,  the  lead 
alloy  was  found  to  contain  96  grammes  of  sodium,  or  17  per 
cent.  There  was  about  90  grammes  of  sodium  found  in  the  tin 
alloy,  or  between  45  and  50  per  cent.  Both  these  alloys  rapidly 
oxidized  in  the  air,  and  when  thrown  into  water  the  action  was 
very  energetic,  in  the  case  of  the  tin  alloy  the  liberated  hydrogen 
being  ignited,  and  after  the  reaction  the  metals  were  found  at  the 
bottom  of  the  vessel  in  a  finely  divided  state.  Both  these  alloys 
reduce  cryolite  or  aluminium  chloride." 

In  Prof.  Rogers'  further  experiments  cryolite  was  added  to  the 
bath,  so  that  sodium  was  produced  and  aluminium  formed  in  one 
operation.  (See  under  "  Electrolytic  Processes/7  Chap.  XI.) 


CHAPTER  VIII. 

THE  REDUCTION  OF  ALUMINIUM  COMPOUNDS  FROM  THE 
STANDPOINT  OF  THERMAL  CHEMISTRY. 

THE  branch  of  chemical  science  called  thermal  chemistry  may 
be  said  to  be  yet  in  its  infancy.  Although  an  immense  mass  of 
thermal  data  has  been  accumulated,  yet  the  era  of  great  gener- 
alizations in  this  subject  has  not  yet  been  reached ;  and  although 
we  know  with  a  fair  degree  of  accuracy  the  heat  of  combination 
of  thousands  of  chemical  compounds,  including  nearly  all  the 
common  ones,  yet  the  proper  way  to  use  these  data  in  predicting 
the  possibility  of  any  proposed  reaction  remains  almost  unknown. 
The  principal  barriers  in  the  way  are  two :  1st,  the  unknown 
quantities  entering  into  almost  every  chemical  reaction  thermally 


184  ALUMINIUM. 

considered,  i.  e.,  the  heat  of  combination  of  elementary  atoms  to 
form  molecules  of  the  elements ;  2d,  the  uncertainty  as  regards 
the  critical  temperature  at  which  a  given  exchange  of  atoms  and 
consequent  reaction  will  take  place.  We  will  explain  what  is 
meant  by  these  statements. 

To  illustrate,  let  us  consider  the  case  of  hydrogen  uniting  with 
oxygen  to  form  water  according  to  the  formula — 

2(H— H)  +  (O  -  O)  =  2  H20 

where  (H — H)  and  (O  =  O)  represent  respectively  molecules  of 
hydrogen  and  oxygen.  Now,  as  1  kilo  of  hydrogen  unites  with 
8  of  oxygen  to  form  9  of  water,  setting  free  34462  units  of  heat 
(calories),  if  we  take  the  atomic  weights  in  the  above  reaction  as 
representing  kilos,  we  shall  have  the  thermal  value  of  the  reaction 
4  X  34462  =  + 137848  calories.  But  this  quantity  is  evidently 
the  algebraic  sum  of  the  heat  evolved  in  the  union  of  4  kilos  of 
hydrogen  atoms  with  32  kilos  of  oxygen  atoms,  and  the  heat 
absorbed  in  decomposing  4  kilos  of  hydrogen  gas  into  atoms, 
and  32  kilos  of  oxygen  gas  into  atoms.  These  two  latter  quanti- 
ties are  unknown,  though  a  few  chemists  have  concluded  from 
studies  on  this  question  that  they  are  probably  very  large.  It 
has  been  calculated  that  the  reaction — 

H  +  H «»  (H— H)  sets  free  240,000  calories, 
and  O  +  O  —  (O  —  O)  sets  free  147,200  calories ; 

but  no  assurance  can  be  placed  on  these  numbers.  If  they  were 
approximately  true,  then 

4H  +  2O  =  2H2O  would  set  free  about  773,000  calories. 

If  these  quantities  are  really  anything  like  so  large,  and  if  they 
are  at  sometime  determined  with  precision,  thermo  -  chemical 
principles  and  conclusions  will  be  greatly  modified.  Meanwhile, 
predictions  based  on  the  data  we  have  lose  all  possibility  of 
certainty,  and  so  we  need  to  keep  in  mind  in  our  further  discuss- 
ion that  our  deductions  at  the  best  can  be  no  more  than  prob- 
abilities. Further,  suppose  that  we  mix  1  kilo  of  hydrogen  gas 
and  8  kilos  of  oxygen  gas,  put  them  in  a  tight  vessel  and  keep 
them  at  the  ordinary  temperature.  No  reaction  will  take  place 
in  any  length  of  time,  even  though  34,462  calories  would  be  set 


REDUCTION   THEORETICALLY   CONSIDERED.  185 

free  thereby.  The  explanation  of  this  is  probably  that  the  atoms 
of  hydrogen  and  oxygen  are  so  firmly  bound  to  each  other  in  the 
molecules,  that  the  dissimilar  atoms  have  not  strength  of  affinity 
sufficient  to  break  away  in  order  to  combine.  However  this  may 
be,  it  is  well  known  that  a  spark  only  is  necessary  to  cause  an 
explosive  combination  of  the  gases  under  the  above  conditions, 
the  temperature  of  the  spark  expanding  the  gases  coming  in 
contact  with  it,  causing  the  atoms  to  swing  with  more  freedom 
in  the  molecules,  and  as  soon  as  two  atoms  of  hydrogen  come 
within  the  sphere  of  attraction  of  an  atom  of  oxygen  and  form 
a  molecule  of  water,  the  heat  liberated  is  immediately  communi- 
cated to  the  adjacent  atoms,  and  almost  instantaneously  the  entire 
gases  have  combined.  The  same  principle  undoubtedly  holds 
true  in  cases  of  reduction.  Carbon  may  be  mixed  with  litharge 
and  the  mixture  left  in  the  cold  forever  without  reacting,  but  at 
a  certain  temperature  the  carbon  will  abstract  the  oxygen.  The 
temperatures  at  which  reactions  of  this  nature  will  take  place 
are  often  determined  experimentally,  but  I  know  of  no  theo- 
retical grounds  on  which  they  can  rationally  be  calculated. 

There  are  other  points  which  are  somewhat  indeterminate  in 
these  discussions,  such  as  the  influence  of  the  relative  masses  of 
the  reacting  bodies,  their  physical  states,  i.  e.y  solid,  liquid  or 
gaseous,  also  the  influence  of  the  physical  conditions  favoring  the 
formation  of  a  certain  compound,  but  the  nature  of  the  subject 
and  the  meagreuess  of  data  in  the  particular  phenomenon  of 
reduction,  render  it  inexpedient  if  not  impracticable  to  take  these 
points  into  consideration. 

Starting  with  the  above  remarks  in  view,  we  will  consider  the 
heat  generated  by  the  combination  of  aluminium  with  certain 
other  elements,  as  has  been  determined  experimentally,  and  study 
from  a  comparison  with  the  corresponding  thermal  data  for  other 
elements,  what  possibilities  are  shown  for  reducing  these  alumin- 
ium compounds. 

The  heat  generated  by  the  combination  of  aluminium  with  the 
different  elements  is  given  as  follows  ;  the  first  column  giving 
the  heat  developed  by  54  kilos  of  aluminium  (representing  Al2), 
and  the  second  the  heat  per  atomic  weight  of  the  other  element, 
e.  g.}  per  16  kilos  of  oxygen. 


186 


ALUMINIUM. 


Element. 
Oxygen 

Chlorine 
Bromine 
Iodine 
Sulphur 


Compound. 


A12C16 


Al2!6 


Calories. 
391,600 
392,600 
321,960 
239,440 
140,780 
124,400 


Calories. 

130,500 

130,900 

53,660 

39,900 

23,460 

41,467 


Authority. 
Bertholet. 
Bailie  &  Fery. 
Thomsen. 


Let  us  consider  the  theoretical  aspect  of  the  reduction  of 
Alumina.  The  heat  given  out  by  other  elements  or  compounds 
which  unite  energetically  with  oxygen  is  as  follows,  the  quantity 
given  being  that  developed  by  combination  with  16  kilos  (rep- 
resenting one  atomic  weight)  of  oxygen. 

Element.  Compound.  Calories. 

Aluminium A12O3  130,500 

Sodium Na20  99,760 

Potassium KaO  100,000  (?) 

Barium BaO  124,240 

Strontium SrO  128,440 

Calcium CaO  130,930 

Magnesium MgO  145,860 

Manganese          .         .         .         .  MnO  95,000  (?) 

Silicon SiO2  110,000 

Zinc ZnO  85,430 

Iron    .         .         .         .         .         .         .  Fe^3  63,700 

Lead PbO  50,300 

Copper CuO  37,160 

Cu*O  40,810 

Sulphur SO2  35,540 

Hydrogen H20  68,360 

Carbon CO  29,000 

" CO2  48,480 

Carbonic  anhydride   ....  CO2  67,960 

Potassium  cyanide      ....  KCyO  72,000 

On  inspecting  this  list  we  find  magnesium  to  be  the  only  metal 
surpassing  aluminium,  while  calcium  is  about  the  same.  This 
would  indicate  that  the  reaction 

APO3  +  3Mg  =  Al2  +  3MgO 

*  Bertholet's  number  represented  the  formation  of  the  hydrated  oxide, 
A1203.3H20,  and,  for  want  of  knowing  the  heat  of  hydration,  has  been  gener- 
ally used  as  the  heat  of  formation  of  A12OV  Recently,  J.  B.  Bailie  and  C. 
Fe>y  (Ann.  de  China,  et  de  Phys.,  June,  1889,  p.  250)  have,  by  oxidizing 
aluminium  amalgam,  obtained  the  above  figure  for  the  heat  of  formation  of 
A1203,  and  determined  that  the  heat  of  hydration  is  3000  calories,  which  would 
make  the  heat  of  formation  of  the  hydrated  oxide  395,600. 


REDUCTION   THEORETICALLY   CONSIDERED.  187 

would,  if  it  were  possible  to  bring  the  alumina  and  magnes- 
ium in  the  proper  conditions  for  reacting,  develop  about 

(145,860—130,500)  x  3  -  46,080  calories, 

and  points  to  the  possibility  of  reducing  alumina  by  nascent, 
molten,  or  vaporized  magnesium,  under  certain  unknown  con- 
ditions. It  may  be  that  molten  alumina  would  be  reduced  by 
vapor  of  magnesium,  but  experiment  only  could  establish  or  deny 
the  possibility  of  the  reaction.  Even  if  this  took  place,  it 
would  probably  not  be  of  practical  importance. 

We  notice  further  the  fact  that  sodium  or  potassium  could  not 
reduce  alumina  without  heat  being  absorbed  in  large  quantity, 
and  it  is  interesting  to  remember  that  some  of  the  first  attempts 
at  isolating  aluminium  by  using  potassium  were  made  on  alumina, 
and  were  unsuccessful,  so  that  it  is  practically  acknowledged  that 
while  these  metals  easily  reduce  other  aluminium  compounds 
(according  to  reactions  which  are  thermally  possible,  as  we  shall 
see  later  on)  yet  they  cannot  reduce  alumina,  under  any  conditions 
so  far  tried. 

When  we  consider  the  case  of  reduction  by  the  ordinary  re- 
ducing agents,  hydrogen,  carbon,  or  potassium  cyanide,  we  are 
confronted  in  every  case  with  large  negative  quantities  of  heat,  i.  e., 
deficits  of  heat.  So  large  do  these  quantities  appear  that  it  is 
very  small  wonder  that  the  impossibility  of  these  reductions  oc- 
curring under  any  conditions  has  been  strongly  affirmed.  For 
instance 

APO3  4-  6H  =  AP  +  3H*0 

would  require 

(130500  —  68360)  X  3     «  186,420  calories. 

A12O3      +  3C       =  AP  +  3CO  304,500  calories. 

APO3      +  1JC     =  Al2  +  HCO2  246,060  calories. 

APO8      +  3KCy  «  AP  +  3KCyO  175,500  calories. 

APO3      +     3CO  =  AP  +  3CO2  187,620  calories. 

From  these  figures,  however,  we  beg  leave  to.disclairn  predicting  the 
absolute  impossibility  of  the  reactions  taking  place ;  the  figures 
simply  point  to  the  probable  impossibility  of  the  reaction,  or  to 
its  possibility  only  under  very  exceptional  conditions.  This 
position  can  be  strengthened  by  considering  that  the  reaction 


188  ALUMINIUM. 

ZnO     -f    C  a.  Zn  +  CO    requires    56,430  cal. 
Fe2O3  -f  3C  -  Fe2  +  SCO        "       104,100  cal. 
PbO    +    C  =  Pb  +  CO          "         21,300  cal. 
yet  these  reactions  are  a  matter  of  every  day  experience.     If  it  be 
claimed  that  ferric  oxide  and  litharge  are  really  reduced  by  car- 
bonic oxide,  according  to  the  reactions 

Fe"O»  +  SCO  =  Fe2  +  SCO2  developing  12,780  cal. 
PbO  4-  CO    -  Pb       CO2  "          17,660    « 

and  therefore  that  the  reduction  is   possible  because  thermally 
positive,  yet 

ZnO  +  CO  =  Zn  +  CO2  requires  17,470  cal. 
and  we  still  have  before  us  a  thermally  negative  reaction,  which 
is  practically  carried  out. 

It  is  thus  apparent  that  the  reduction  of  alumina  by  the  com- 
mon reducing  agents  is,  thermally  considered,  not  an  absolutely 
impossible  question  but  one  which  presents,  possibly,  as  much 
greater  difficulty  over  the  reduction  of  zinc  oxide  or  iron  ore  as 
the  heat  deficit  is  greater  in  one  case  than  in  the  other. 

The  question  may  be  asked,  "  On  what  grounds  has  it  been 
calculated  that  carbon  will  reduce  alumina  at  a  temperature  of 
10000°  C.  ?"  I  have  seen  this  statement  in  print,  and  was  for 
some  time  at  a  loss  to  understand  how  this  result  was  obtained, 
but  came  finally  to  the  conclusion  that  it  must  have  been  deduced 
from  the  following  premises  : — 

The  reaction  A12O3  +  3C  «*  Al2  +  SCO  shows  a  deficit  of 
304500  calories.  If,  therefore,  304500  heat  units  can  in  some 
way  be  added  to  the  alumina  and  carbon,  then  they  might 
probably  be  induced  to  react.  Evidently  then,  if  we  heat  these 
substances  they  absorb  a  certain  number  of  heat  units  for  every 
degree  rise  of  temperature,  and  at  some  certain  temperature  will 
have  absorbed  the  required  number  of  heat  units  to  induce  the 
reaction.  The  calculation  seems  to  have  been  made  thus — 
Weight  of  alumina  X  specific  heat. 

102  x  0.2         «  20.4 

Weight  of  carbon    x  specific  heat. 

36  X  0.25      -     9. 

Caloric  capacity  per  degree  29.4  calories. 


REDUCTION    THEORETICALLY   CONSIDERED.  189 

The  temperature  to  which  the  alumina  and  carbon  must  be 
heated  in  order  to  absorb  304,500  calories  must  be — 

304502=s  10350° C. 
29.4 

There  are  several  sources  of  error  which  will  be  immediately 
pointed  out  in  this  calculation.  For  instance,  specific  heats  are 
known  to  increase  with  the  temperature,  while  in  the  case  of 
carbon  its  specific  heat  at  a  red  heat  is  known  to  be  about  0.46. 
Making  this  correction  alone  would  reduce  the  temperature 
needed  to  about  8200°  C. 

That  this  method  of  figuring  is  not  entirely  unreasonable 
seems  probable  when  we  apply  it  to  the  reduction  of  oxide  of 
zinc  by  carbonic  oxide ;  for,  in  the  case  of  the  reaction, 
ZnO  +  CO  =  Zn  +  CO2,  the  temperature  calculated  would  be 

(sr^^lSrSlr  =  TTT  =  1020°>whichisvery 

close  to  the  observed  temperature.  Yet  we  are  constrained  to 
regard  this  coincidence  as  fortuitous,  since  the  same  calculations 
for  other  oxides  do  not  agree  with  the  observed  values.  The 
method,  if  applied  to  the  reduction  of  alumina  by  carbonic  oxide, 
would  give  about  4500°  C. ;  but  it  is  certain,  from  what  we  know 
of  the  dissociation  of  carbonic  acid  by  heat,  that  far  below  this 
temperature  carbonic  oxide  loses  almost  all  its  affinity  for  oxygen, 
and  this  result  must  be  rejected  as  mythical.  The  result  obtained 
for  reduction  by  carbon,  forming  CO,  is  open  to  a  similar  objec- 
tion, owing  to  the  fact  that  at  very  high  temperatures  carbonic 
oxide  also  is  dissociated,  but  the  dissociation  takes  place  so  slowly 
and  to  such  a  small  degree  within  observable  temperatures,  that 
it  is  not  impossible  that  alumina  may  be  reduced  by  carbon  at 
temperatures  within  the  above-named  limits. 

The  reduction  of  alumina  by  hydrogen,  calculated  by  this 
method,  would  take  place  at  4500°,  but  since  water  is  dissociated 
at  high  temperatures,  this  figure  is  open  to  the  same  criticism  as 
that  obtained  for  carbonic  oxide.  The  lowest  calculated  value 
for  the  temperature  of  reduction  of  alumina  is  given  by  potas- 
sium cyanide,  for  the  reaction 

Al20a  H-  3KCy  =  Al2  +  3KCyO 


190 


ALUMINIUM. 


would  require  an  addition  of  175,600  cal.,  which  would  necessi- 
tate heating  the  substances  to  about  3000°  (using  the  most  prob- 
able value  for  the  specific  heat  of  potassium  cyanide  —0.2). 
Whether  potassium  cyauate  (KCyO)  dissociates  sensibly  at  this 
temperature  I  cannot  say,  but  the  fact  remains  that  if  the  tem- 
peratures calculated  by  this  method  are  worthy  of  any  credibility 
at  all,  they  point  to  potassium  cyanide  as  likely  to  reduce  alumina 
at  a  lower  temperature  than  either  hydrogen,  carbonic  oxide,  or 
carbon. 

As  the  basis  of  our  discussion  of  the  reduction  of  aluminium 
chloride,  bromide,  or  iodide,  we  give  a  table  of  the  heat  developed 
by  the  combination  of  some  of  the  elements  with  one  atomic 
weight  (in  kilos)  of  each  of  these  haloids. 


Element. 

Com- 
pound. 

Calories. 

Com- 
pound. 

Calories. 

Com- 
pound. 

Calories. 

Aluminium   .     .     . 
Potassium   .... 

A12C16 

KC1 
NaCl 

53,660 

305,600 
97,690 

AFBr5 

KBr 
NaBr 

40,000 

95,300 
85,700 

Al2!6 

KI 
Nal 

23,460 

80,100 
69,000 

Lithium       .... 

LiCl 
Bad2 

93,810 
97,370 

BaBr2 

85,000 

Strontium   .... 
Calcium       .... 
Magnesium       .     .     . 
Manganese       .     .     . 

SrCl* 
Cad2 
MgCl2 
MnCl2 

ZnCl2 

92,270 
84,910 
75,500 
56,000 

(  50,600f 

SrBr2 
CaBr' 

ZnBr* 

78,900 
70,400 

(43,  100J 
•{  40,640f 

Znl8 

f30,000t 
•1  26,600 

Lead            .... 

PbCl2 

\  48,  600* 
41,380 

PbBi-2 

^37,500* 
32,200 

Pbl2 

124,500 
20,000 

Mercury      .... 
Tin    

HgzCl2 
SnCl2 

41,275 

40,400 

Hg2Br2 

34,150 

Hg2!2 

24,200 

Fed2 

41,000 

FeBr2 

24,000 

Pel2 

8,000f 

Cu2Cl2 

32,875 

Cu2Br2 

25,000 

Cu2!2 

16,000 

Hydrogen    .... 

Hd 

22,000 

HBr 

8,400 

HI 

—6,000 

*  Thomson.  f  Andrews, 

t  Jahresbericht  der  Chemie,  1878,  p.  102. 


On  inspecting  this  table  we  notice  that,  in  general,  all  the 
metals  down  to  zinc  develop  more  heat  in  forming  chlorides  and 
very  probably  also  in  forming  bromides  and  iodides.  A  reaction, 
then,  between  aluminium  chloride  and  any  of  these  metals,  form- 
ing aluminium  and  a  chloride  of  the  metal,  would  be  exothermic, 
which  means,  generally  speaking,  that  if  aluminium  chloride  and 


SEDUCTION   THEORETICALLY   CONSIDERED.  191 

any  one  of  these  metals  were  heated  together  to  the  critical  point 
at  which  the  reaction  could  begin,  the  reaction  would  then  pro- 
ceed of  itself,  being  continued  by  the  heat  given  out  by  the  first 
portions  which  reacted.  Zinc  seems  to  lie  on  the  border  line,  and 
the  evidence  as  to  whether  zinc  will  practically  reduce  these 
aluminium  compounds  is  still  contradictory,  as  may  be  seen  by  ex- 
amining the  paragraphs  under  "  Reduction  by  Zinc."  (Chap.  XII.) 
Of  the  first  six  metals  mentioned  in  the  table  after  aluminium, 
Duly  potassium  and  sodium  are  practically  available.  The  reac- 
tion 

A12C16  +  6K    =  Al2  +  6KC1  develops  311,640  cal. 

APC16  +  6Na  =  Al2  +  6NaCl  develops  264,180  cal. 

and  the  result  of  this  strong  disengagement  of  heat  is  seen  when, 
on  warming  these  ingredients  together,  the  reaction  once  com- 
menced at  a  single  spot  all  external  heat  can  be  cut  off,  and  the 
resulting  fusion  will  become  almost  white  hot  with  the  heat  de- 
veloped. In  fact,  the  heat  developed  in  the  second  reaction 
would  theoretically  be  sufficient  to  heat  the  aluminium  and 
sodium  chloride  produced  to  a  temperature  between  3000°  and 
4000°  C. 

Magnesium  should  act  in  a  similar  manner,  though  not  so  vio- 
lently, since 

A12C16  +  3Mg  =  Al2  +  3MgCl2  develops  131,000  cal. 
And  manganese  possibly  also,  since 

A12C16  +  3Mn  .=  Al2  +  3MnCl  develops  14,040  cal. 

The  reduction  of  aluminium  chloride,  bromide,  or  iodide  by 
hydrogen  is  thermally  strongly  negative,  which  would  indicate  a 
very  small  possibility  of  the  conditions  ever  being  arranged  so  as 
to  render  the  reaction  possible.  For  instance,  taking  the  most 
probable  case, 

A12C16  +  6H  =  Al2  +  6HC1  requires  189,960  calories.  More- 
over, a  calculation  similar  to  those  made  on  the  reduction  of 
alumina  by  carbon  would  show  a  theoretical  temperature  of 
2500°  C.  necessary  to  cause  the  reaction,  if  the  energy  required 
were  added  in  the  shape  of  heat. 

The  only  probable  substitutes  for  sodium  in  reducing  alumin- 


192  ALUMINIUM. 

ium  chloride  are  thus  seen  to  be  magnesium  (whose  cost  will 
probably  be  always  greater  than  that  of  aluminium),  manganese 
(which  may  sometime  be  used  in  the  form  of  ferro-manganese  for 
producing  ferro-aluminium),  and  zinc  (whose  successful  applica- 
tion to  this  purpose  would  be  a  most  promising  advance  in  the 
metallurgy  of  aluminium). 

The  heat  of  combination  of  fluorides  is  unknown,  and  so 
what  would  be  an  inquiry  of  interest  with  regard  to  these  salts 
is  out  of  our  reach.  We  know,  however,  from  experiment,  that 
sodium  will  displace  aluminium  in  its  fluoride,  developing  a  great 
deal  of  heat  in  the  reaction,  so  that  it  is  probable  that  the  thermal 
relations  of  elements  towards  fluorine  are  similar  to  those  towards 
chlorine.  We  can  venture  nothing  further  than  this  general 
observation. 

In  order  to  discuss  the  thermal  relations  of  aluminium  sul- 
phide, we  will  make  use  of  the  following  data,  the  heat  developed 
being  per  atomic  weight  (32  kilos)  of  sulphur  combining  : — 

Element.  Compound.  Calories. 

Aluminium A12S3  41,467 

Potassium K2S  103,700 

Sodium Na2S  88,200 

Calcium CaS  92,000 

Strontium SrS  99,200 

Magnesium          .         .         .         .         .  MgS  79,600 

Manganese MnS  46,400 

Zinc ZnS  41,326 

Iron FeS  23,576 

Copper Cu*S  20,270 

Lead PbS  20,430 

Hydrogen R2S  4,740 

Carbon CS*  —26,010 

These  figures  point  to  the  easy  reduction  of  aluminium  sul- 
phide by  potassium,  sodium,  or  magnesium,  and  possibly  by 
manganese  and  zinc.  The  other  metals  would  require  exceptional 
conditions,  perhaps  of  temperature,  for  their  action.  It  is  in- 
teresting to  note,  as  illustrating  the  many  difficult  points  to  be 
mastered  by  a  consistent  theory  of  the  thermo-chemistry  of  re- 
duction, that  two  observers  at  least  have  determined  (probably 
from  the  deposition  of  the  metals  from  solution  by  hydrogen 


REDUCTION   THEORETICALLY   CONSIDERED.  193 

sulphide),  that  the  order  of  the  affinity  of  the  metals  for  sulphur 
is  first  the  alkaline  metals,  then  the  others  in  the  following  order: 
copper,  lead,  zinc,  iron,  manganese,  and  then  aluminium  and 
magnesium — with  the  remark  that  the  affinities  of  the  latter  two 
for  sulphur  appear  quite  insignificant.  We  are  unable  to  sug- 
gest the  meaning  of  the  discrepancy  here  seen,  it  may  be  that 
when  the  metals  are  in  solution  some  other  circumstances  beside 
the  heat  of  combination  may  have  the  controlling  influence  in 
deciding  which  one  of  the  metals  would  be  first  precipitated, 
such  as  the  degree  of  acidity  of  the  solution,  etc.  It  is  altogether 
probable  that  in  reactions  in  the  dry  way,  by  heat,  the  order  of 
affinity  of  the  metals  for  sulphur  would  more  nearly  correspond 
to  the  order  seen  in  the  heats  of  combination. 

The  reduction  of  aluminium  sulphide  by  hydrogen  is  seen  to 
appear  highly  improbable. 


Before  closing  this  study  of  the  thermal  aspect  of  the  reduction 
of  aluminium  compounds,  it  may  be  interesting  to  notice  some  of 
the  reactions  which  are  of  use  in  the  aluminium  industry.  It  is 
well  known  that  while  chlorine  gas  can  be  passed  over  ignited 
alumina  without  forming  aluminium  chloride,  and  while  carbon 
can  be  in  contact  with  alumina  at  a  white  heat  without  reducing 
it,  yet  the  concurrent  action  of  chlorine  and  carbon  will  change 
the  alumina  into  its  chloride,  a  compound  with  a  lower  heat  of 
formation.  Thus — 

A12O3  -f  3C  =  Al2  -f  3CO  requires  304,500  cal. 

But  A12O3  -f  3C  4-  6C1  =  A12C16  +  3CO  requires  a  quantity  of 
heat  equal  to  the  304500  cal.  minus  321960,  the  heat  of  forma- 
tion of  aluminium  chloride,  or  in  other  words  17360  cal.  is 
evolved,  showing  that  the  reaction  is  one  of  easy  practicability. 
If  it  be  inquired  whether  there  is  not  some  chloride  which  would 
act  on  alumina  to  convert  it  into  chloride,  we  would  remark  that 
if  we  can  find  a  chloride  whose  heat  of  formation  is  as  much 
greater  than  the  heat  of  formation  of  the  corresponding  oxide  as 
the  heat  of  formation  of  aluminium  chloride  is  greater  than  that  of 
alumina,  then  such  a  chloride  might  react.  To  be  more  particular, 
to  convert  alumina  into  aluminium  chloride,  a  deficit  of  391600  — 
13 


194  ALUMINIUM. 

321960  or  69640  calories  must  be  made  up.  If  we  know  of  an 
element  which  in  uniting  with  3  atom  weights  (48  kilos)  of 
oxygen  gives  out  69640  calories  more  heat,  or  a  still  greater 
excess,  than  in  uniting  with  6  atom  weights  (213  kilos)  of  chlor- 
ine, then  the  chloride  of  that  element  might  perform  the  reaction. 
Now— 

6Na  +  3O  =  3Na2O  evolves  299,280  cal. 
and      6Na  +  6C1  =  6NaCl  evolves  586,140  cal. 

leaving  evidently  a  balance  of  286,860  calories  in  the  opposite 
direction  to  what  we  are  looking  for.  And  so  for  every  metal 
except  aluminium,  I  find  the  heat  of  formation  of  its  chloride 
greater  t  than  that  of  an  equivalent  quantity  of  its  oxide.  The 
only  element  which  I  know  of  which  possesses  the  opposite  prop- 
erty is  hydrogen,  for — 

6H  +  3O  _  3H2O  evolves  205,080  cal. 
and        6H  +  6C1  =  6HC1  evolves  132,000  cal. 

and  therefore  the  reaction — 

AW  +6HC1  -  A12C16  +3H2O 

would  evolve  according  to  our  calculations  (205,080  — 132,000)  — 
69640  or  3440  calories,  and  would  be  thermally  considered  a  pos- 
sible reaction.  Moreover,  as  a  secondary  effect,  the  water  formed 
is  immediately  seized  by  the  aluminium  chloride,  for  the  reaction 

A12C16  +3H2O      A12C16.3H2O  evolves  153,690  cal. 

and  thus  increases  the  total  heat  developed  in  the  decomposition 
of  the  alumina  to  158,130  calories.  The  result  of  this  reaction 
is  therefore  the  hydrated  chloride,  which  is  of  no  value  for  re- 
duction by  sodium,  since  when  heated  it  decomposes  into  alumina 
and  hydrochloric  acid  again,  that  is,  it  will  decompose  before 
giving  up  its  water,  and  the  water  if  undecomposed,  or  the  acid 
if  it  decomposes,  simply  unites  with  the  sodium  without  affecting 
the  alumina.  The  immense  heat  of  hydration,  1 53,690  calories,  is 
so  much  greater  than  that  of  any  other  known  substance,  that  it 
is  in  vain  that  we  seek  for  any  material  which  might  abstract  the 
water  and  leave  anhydrous  aluminium  chloride. 

Analogous  to  the  reaction   by  which   aluminium  chloride  is 


REDUCTION   THEORETICALLY   CONSIDERED.  195 

formed  from  alumina  is  the  reaction  made  use  of  for  obtaining 
aluminium  sulphide,  yet  with  some  thermal  considerations  of  a 
different  and  highly  interesting  kind.  If  a  mixture  of  alumina 
and  carbon  is  ignited  and,  instead  of  chlorine,  sulphur  vapor  is 
passed  over  it,  no  aluminium  sulphide  will  be  formed.  An  ex- 
planation of  this  fact  is  seen  on  discussing  the  proposed  reaction 
thermally. 

APO3  +  3C  +  38  =  APS3  +  SCO  requires  180,200  cal. 

It  will  be  remembered  that  the  similar  reaction  with  chlorine 
evolved  17,360  calories ;  the  quantity  causing  this  diiference 
is  the  heat  of  combination  of  aluminium  sulphide,  which  is 
321,960  —  124,400  _  197,560  calories  less  than  that  of  alu- 
minium chloride,  changing  the  excess  of  17,360  calories  into  a 
deficit  of  180,200  calories.  This  large  negative  quantity  shows 
a  priori  that  the  reaction  could  be  made  to  occur  only  under  ex- 
ceptional conditions,  and  its  uon -occurrence  under  all  conditions 
so  far  tried  gives  evidence  of  the  utility  of  the  study  of  thermo- 
chemistry, at  least  as  a  guide  to  experiment.  However,  while 
carbon  and  sulphur  cannot  convert  alumina  into  aluminium  sul- 
phide, carbon  bisulphide  can,  for  a  current  of  the  latter  led  over 
ignited  alumina  converts  it  into  aluminium  sulphide.  The  reac- 
tion taking  place  is 

APO3  +  3CS2  =  APS3  +  3COS. 

Now,  since  carbon  and  sulphur  by  themselves  could  not  perform 
the  reaction,  we  should  be  very  apt  to  reason  that  a  compound  of 
carbon  and  sulphur  would  be  still  less  able  to  do  so,  since  the 
heat  absorbed  in  dissociating  the  carbon-sulphur  compound  would 
cause  a  still  greater  deficit  of  heat.  But  here  is  precisely  the  ex- 
planation of  the  paradox.  Carbon  bisulphide  is  one  of  those 
compounds,  not  frequent,  which  has  a  negative  heat  of  formation 
( — 26,010  calories),  i.  e.,  heat  is  absorbed  in  large  quantity  in  its 
formation,  and  therefore,  per  contra,  heat  is  given  out  in  the 
same  quantity  in  its  decomposition.  The  heat  of  formation  of 
carbon  oxysulphide  being  37,030  calories,  we  can  easily  compute 
the  thermal  value  of  the  reaction  just  given. 


196  ALUMINIUM. 

Heat  absorbed. 
Decomposition  of  alumina       .....        391,600  cal. 

Heat  developed. 

Decomposition  of  carbon  bisulphide         .       78,030 

Formation  of  carbon  oxysulphide    .         .     111,090 

"         of  aluminium  sulphide   .         .     124,400 

313,520   " 


Deficit  of  heat       .         .         .         .          78,080    " 

It  is  thus  seen  that  the  reaction  with  carbon  bisulphide  is  less 
than  one-half  as  strongly  negative  as  the  reaction  with  carbon 
and  sulphur  alone,  and  in  accordance  with  this  we  have  the  fact 
that  aluminium  sulphide  is  produced  when  carbon  bisulphide 
vapor  is  passed  over  alumina  heated  white  hot,  while  it  is  still 
further  interesting  to  note  that  the  presence  of  carbon  mixed  with 
the  alumina  is  of  no  aid  at  all  to  the  reaction. 


CHAPTER  IX. 

REDUCTION  OF  ALUMINIUM  COMPOUNDS  BY  MEANS  OF 
POTASSIUM  OR  SODIUM. 

THE   methods   comprised   under  this   heading  may  be   con- 
veniently divided  into  three  classes  : — 

I.  Methods  based  on  the  reduction  of  aluminium  chloride 

or  aluminium-sodium  chloride. 
II.  Methods  based  on  the  reduction  of  cryolite. 
III.  Methods  based  on  the  reduction  of  aluminium  fluoride. 

I. 

The  methods  here  included  can  be  most  logically  presented  by 
taking  them  in  chronological  order. 

Oersted? s  Experiments  (1824). 

After  Davy's  unsuccessful  attempts  to  isolate  aluminium  by 
the  battery,  in  1807,  the  next  chemist  to  publish  an  account  of 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  197 

attempts  in  this  direction  was  Oerstedt,  who  published  a  paper 
in  1824  in  a  Swedish  periodical.*  Oersted  t's  original  paper  is 
thus  translated  into  Berzelius's  ''  Jahresbericht  :"f 

"  Oerstedt  mixes  calcined  and  pure  alumina,  quite  freshly  pre- 
pared, with  powdered  charcoal,  puts  it  in  a  porcelain  retort, 
ignites  and  leads  chlorine  gas  through.  The  coal  then  reduces 
the  alumina,  and  there  results  aluminium  chloride  and  carbonic 
oxide,  and  perhaps  also  some  phosgene,  COC12 ;  the  aluminium 
chloride  is  caught  in  the  condenser  and  the  gases  escape.  The 
sublimate  is  white,  crystalline,  melts  about  the  temperature  of 
boiling  water,  easily  attracts  moisture,  and  evolves  heat  when  in 
contact  with  water.  If  it  is  mixed  with  a  concentrated  potass- 
ium amalgam  and  heated  quickly,  it  is  transformed ;  there  results 
potassium  chloride,  and  the  aluminium  unites  with  the  mercury. 
The  new  amalgam  oxidizes  in  the  air  very  quickly,  and  gives  as 
residue  when  distilled  in  a  vacuum  a  lump  of  metal  resembling 
tin  in  color  and  lustre.  In  addition,  Oerstedt  found  many  re- 
markable properties  of  the  metal  and  of  the  amalgam,  but  he 
holds  them  for  a  future  communication  after  further  investiga- 
tion." 

Oerstedt  did  not  publish  any  other  paper,  and -the  next  advance 
in  the  science  is  credited  to  Wohler,  whom  all  agree  in  naming  as 
the  true  discoverer  of  the  metal. 


Wohler's  Experiments  (1827). 

In  the  following  article  from  PoggendorfFs  Annalen,J  Wohler 
reviews  the  article  of  Oerstedt's  given  above,  and  continues  as 
follows : — 

"  I  have  repeated  this  experiment  of  Oerstedt,  but  achieved 
no  very  satisfactory  result.  By  heating  potassium  amalgam  with 
aluminium  chloride  and  distilling  the  product,  there  remained 
behind  a  gray,  melted  mass  of  metal,  but  which,  by  raising  the 
heat  to  redness,  went  oif  as  green  vapor  and  distilled  as  pure 

*  Oversigt  over  det  K.     Danske  Videnskabemes  Selkabs   Forhandlingar  og 
dels  Medlemmers  Arbeider.     May,  1824,  to  May,  1825,  p.  15. 
f  Berz.  Jahresb.  der  Chemie,  1827,  vi.  118. 
t  Pogg.  Ann.,  1827,  ii.  147. 


198  ALUMINIUM. 

potassium.  I  have  therefore  looked  around  for  another  method 
or  way  of  conducting  the  operation,  but,  unpleasant  as  it  is  to  say 
it,  the  reduction  of  the  aluminium  fails  each  time.  Since,  how- 
ever, Herr  Oerstedt  remarks  at  the  end  of  his  paper  that  he  did 
not  regard  his  investigations  in  aluminium  as  yet  ended,  and 
already  several  years  have  passed  since  then,  it  looks  as  if  I  had 
taken  up  one  of  those  researches  begun  auspiciously  by  another 
(but  not  finished  by  him),  because  it  promised  new  and  splendid 
results.  I  must  remark,  however,  that  Herr  Oerstedt  has  indi- 
rectly by  his  silence  encouraged  me  to  try  to  attain  to  further 
results  myself.  Before  I  give  the  art  how  one  can  quite  easily 
reduce  the  metal,  I  will  say  a  few  words  about  aluminium  chloride 
and  its  production  (see  p.  1 22). 

"I  based  the  method  of  reducing  aluminium  on  the  reaction  of 
aluminium  chloride  on  potassium,  and  on  the  property  of  the 
metal  not  to  oxidize  in  water.  I  warmed  in  a  glass  retort  a  small 
piece  of  the  aluminium  salt  with  some  potassium,  and  the  retort  was 
shattered  with  a  strong  explosion.  I  tried  then  to  do  it  in  a 
small  platinum  crucible,  in  which  it  succeeded  very  well.  The 
reaction  is  always  so  violent  that  the  cover  must  be  weighted 
down,  or  it  will  be  blown  off;  and  at  the  moment  of  reduction, 
although  the  crucible  be  only  feebly  heated  from  outside,  it  sud- 
denly glows  inside,  and  the  platinum  is  almost  torn  by  the  sudden 
shocks.  In  order  to  avoid  any  mixture  of  platinum  with  the 
reduced  aluminium,  I  next  made  the  reduction  in  a  porcelain 
crucible  and  succeeded  then  in  the  following  manner :  Put  in  the 
bottom  of  the  crucible  a  piece  of  potassium  free  from  carbon  and 
oil,  and  cover  this  with  an  equal  volume  of  pieces  of  aluminium 
chloride.  Cover,  and  heat  over  a  spirit  lamp,  at  first  gently,  that 
the  crucible  be  not  broken  by  the  production  of  heat  inside,  and 
then  heat  stronger,  at  last  to  redness.  Cool,  and  when  fully  cold 
put  it  into  a  glass  of  cold  water.  A  gray  powder  separates  out, 
which  on  nearer  observation,  especially  in  sunlight,  is  seen  to  con- 
sist of  little  flakes  of  metal.  After  it  has  separated,  pour  off  the 
solution,  filter,  wash  with  cold  water,  and  dry ;  this  is  the  alu- 
minium." 

In  reality,  this  powder  possessed  no  metallic  properties,  and 
moreover,  it  contained  potassium  and  aluminium  chloride,  which 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  199 

gave  to  it  the  property  of  decomposing  water  at  100°.  To  avoid 
the  loss  of  aluminium  chloride  by  volatilization  at  the  high  heat 
developed  during  the  reaction,  Liebig  afterwards  made  its  vapor 
pass  slowly  over  some  potassium  placed  in  a  long  glass  tube. 
This  device  of  Liebig  is  nearly  the  arrangement  which  Wohler 
adopted  later,  in  1845,  and  which  gave  him  much  better  results. 

Wohler' s  Experiments  (1845). 

The  following  is  Wohler' s  second  paper,  published  in  1845  : — * 
"  On  account  of  the  violent  incandescence  with  which  the  re- 
duction of  aluminium  chloride  by  potassium  is  accompanied,  this 
operation  requires  great  precautions,  and  can  be  carried  out  only 
on  a  small  scale.  I  took  for  the  operation  a  platinum  tube,  in 
which  I  placed  aluminium  chloride,  and  near  it  some  potassium 
in  a  platinum  boat.  I  heated  the  tube  gently  at  first,  then  to 
redness.  But  the  reduction  may  also  be  done  by  putting  potass- 
ium in  a  small  crucible  which  is  placed  inside  a  larger  one,  and 
the  space  between  the  two  filled  with  aluminium  chloride.  A  close 
cover  is  put  over  the  whole  and  it  is  heated.  Equal  volumes  of 
potassium  and  the  aluminium  salt  are  the  best  proportions  to 
employ.  After  cooling,  the  tube  or  crucible  is  put  in  a  vessel  of 
water.  The  metal  is  obtained  as  a  gray  metallic  powder,  but  on 
closer  observation  one  can  see  even  with  the  naked  eye  small  tin- 
white  globules,  some  as  large  as  pins'  heads.  Under  the  micro- 
scope magnifying  two  hundred  diameters  the  whole  powder 
resolves  itself  into  small  globules,  several  of  which  may  sometimes 
be  seen  sticking  together,  showing  that  the  metal  was  melted  at  the 
moment  of  reduction.  A  beaten  out  globule  may  be  again  melted 
to  a  sphere  in  a  bead  of  borax  or  salt  of  phosphorus,  but  rapidly 
oxidizes  during  the  operation,  and  if  the  heat  is  continued  disap- 
pears entirely,  seeming  either  to  reduce  boric  acid  in  the  borax  bead 
or  phosphoric  acid  in  the  salt  of  phosphorus  bead.  I  did  not 
succeed  in  melting  together  the  pulverulent  aluminium  in  a 
crucible  with  borax,  at  a  temperature  which  would  have  melted 
cast-iron,  for  the  metal  disappeared  entirely  and  the  borax  became 

*  Liebig's  Annalen,  53,  422. 


200  ALUMINIUM. 

a  black  slag.  It  seems  probable  that  aluminium,  being  lighter 
than  molten  borax,  swims  on  it  and  burns.  The  white  metallic 
globules  had  the  color  and  lustre  of  tin.  It  is  perfectly  malleable 
and  can  be  hammered  out  to  the  thinnest  leaves.  Its  specific 
gravity,  determined  with  two  globules  weighing  32  milligrammes, 
was  2.50,  and  with  three  hammered-out  globules  weighing  34 
milligrammes,  2.67.  On  account  of  their  lightness  these  figures 
can  only  be  approximate.  It  is  not  magnetic,  remains  white  in 
the  air,  decomposes  water  at  100°,  not  at  usual  temperatures,  and 
dissolves  completely  in  caustic  potash  (KOH).  When  heated  in 
oxygen  almost  to  melting,  it  is  only  superficially  oxidized,  but  it 
burns  like  zinc  in  a  blast-lamp  flame." 

These  results  of  Wohler's,  especially  the  determination  of  spe- 
cific gravity,  were  singularly  accurate  when  we  consider  that  he 
established  them  working  with  microscopic  bits  of  the  metal.  It 
was  just  such  work  that  established  Wbhler's  fame  as  an  investi- 
gator. However,  we  notice  that  his  metal  differed  from  alumin- 
ium as  we  know  it  in  several  important  respects,  in  speaking  of 
wrhich  Deville  says  :  "  All  this  time  the  metal  obtained  by  Wohler 
was  far  from  being  pure  ;  it  was  very  difficultly  fusible,  owing 
without  doubt  to  the  fact  that  it  contained  platinum  taken  from 
the  vessel  in  which  it  had  been  prepared.  It  is  well  known  that 
these  two  metals  combine  very  easily  at  a  gentle  heat.  Moreover 
it  decomposed  water  at  100°,  which  must  be  attributed  either  to 
the  presence  of  potassium  or  to  aluminium  chloride,  with  which 
the  metal  might  have  been  impregnated  :  for  aluminium  in  pre- 
sence of  aluminium  chloride  in  effect  decomposes  water  with 
evolution  of  hydrogen." 

After  Wohler's  paper  in  1845,  the  next  improvement  is  that 
introduced  by  Deville  in  1854-55,  and  this  is  really  the  date  at 
which  aluminium,  the  metal,  became  known  and  its  true  proper- 
ties established. 

Deville' s  Experiments  (1854). 

The  results  of  this  chemist's  investigations  and  success  in  ob- 
taining pure  aluminium  were  first  made  public  at  the  seance  of 
the  French  Academy,  August  14,  1854,  and  included  mention  of 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  201 

an  electrolytic  method  of  reduction  (see  Chap.  XI.),  as  well  as  of 
following  on  reduction  by  sodium.* 

"  The  following  is  the  best  method  for  obtaining  aluminium 
chemically  pure  in  the  laboratory.  Take  a  large  glass  tube  about 
four  centimetres  in  diameter,  and  put  into  it  200  to  300  grammes 
of  pure  aluminium  chloride  free  from  iron,  and  isolate  it  between 
two  stoppers  of  amianthus  (fine,  silky  asbestos).  Hydrogen,  well 
dried  and  free  from  air,  is  brought  in  at  one  end  of  the  tube.  The 
aluminium  chloride  is  heated  in  this  current  of  gas  by  some  lumps 
of  charcoal,  in  order  to  drive  off  hydrochloric  acid  or  sulphides 
of  chlorine  or  of  silicon,  with  which  it  is  always  impregnated. 
Then  there  are  introduced  into  the  tube  porcelain  boats,  as  large 
as  possible,  each  containing  several  grammes  of  sodium,  which 
wras  previously  rubbed  quite  dry  between  leaves  of  filter  paper. 
The  tube  being  full  of  hydrogen,  the  sodium  is  melted,  the  alu- 
minium chloride  is  heated  and  distils,  and  decomposes  in  contact 
with  the  sodium  with  incandescence,  the  intensity  of  which  can 
be  moderated  at  pleasure.  The  operation  is  ended  when  all  the 
sodium  has  disappeared,  and  when  the  sodium  chloride  formed 
has  absorbed  so  much  aluminium  chloride  as  to  be  saturated  with 
it.  The  aluminium  which  has  been  formed  is  held  in  the  double 
chloride  of  sodium  and  aluminium,  Al2Cl6.2NaCl,  a  compound 
very  fusible  and  very  volatile.  The  boats  are  then  taken  from 
the  glass  tube,  and  their  entire  contents  put  in  boats  made  of  re- 
tort carbon,  which  have  been  previously  heated  in  dry  chlorine  in 
order  to  remove  all  silicious  and  ferruginous  matter.  These  are 
then  introduced  into  a  large  porcelain  tube,  furnished  with  a  pro- 
longation and  traversed  by  a  current  of  hydrogen,  dry  and  free 
from  air.  This  tube  being  then  heated  to  bright  redness,  the  alu- 
minium-sodium chloride  distils  without  decomposition  and  con- 
denses in  the  prolongation.  There  is  found  in  the  boats,  after  the 
operation,  all  the  aluminium  which  had  been  reduced,  collected  in 
at  most  one  or  two  small  buttons.  The  boats  when  taken  from  the 
tube  should  be  nearly  free  from  aluminium-sodium  chloride  and 

*  Ann.  de  Phys.  et  de  Chem.,  xliii.  24. 


202  ALUMINIUM. 

also  from  sodium  chloride.  The  buttons  of  aluminium  are  united 
in  a  small  earthen  crucible  which  is  heated  as  gently  as  possible, 
just  sufficient  to  melt  the  metal.  The  latter  is  pressed  together 
and  skimmed  clean  by  a  small  rod  or  tube  of  clay.  The  metal 
thus  collected  may  be  very  suitably  cast  in  an  ingot  mould." 

The  later  precautions  added  to  the  above  given  process  were 
principally  directed  towards  avoiding  the  attacking  of  the  crucible, 
which  always  takes  place  when  the  metal  is  melted  with  a  flux, 
and  the  aluminium  thereby  made  more  or  less  siliceous.  The 
year  following  |the  publication  of  these  results,  this  laboratory 
method  was  carried  out  on  a  large  scale  at  the  chemical  works  at 
Javel. 

Devilled  Methods  (1855). 

The  methods  about  to  be  given  are  those  which  were  devised 
in  Deville's  laboratory  at  the  Ecole  Normale,  during  the  winter 
of  1854-55,  and  applied  on  a  large  scale  at  Javel,  during  the 
spring  of  1855  (March-July).  The  Emperor  Napoleon  III. 
defrayed  the  expenses  of  this  installation.  Descriptions  of  the 
methods  used  for  producing  alumina,  aluminium  chloride  and 
sodium  at  Javel  can  be  found  under  their  respective  headings 
(pp.  106,  120,  123,  146).  We  here  confine  our  description  to  the 
mode  of  reducing  the  aluminium  chloride  by  sodium,  and  the  re- 
marks incident  thereto.  The  process  has  at  present  only  an  his- 
toric interest,  as  it  was  soon  modified  in  its  details  so  as  to  be 
almost  entirely  changed.  The  following  is  Deville's  description  : — 

"  Perfectly  pure  aluminium. — To  obtain  aluminium  perfectly 
pure  it  is  necessary  to  employ  materials  of  absolute  purity,  to 
reduce  the  metal  in  presence  of  a  completely  volatile  flux,  and 
finally  never  to  heat,  especially  with  a  flux,  in  a  siliceous  vessel  to 
a  high  temperature." 

"Pure  materials. — The  necessity  of  using  absolutely  pure 
materials  is  easy  to  understand ;  all  the  metallic  impurities  are 
concentrated  in  the  aluminium,  and  unfortunately  I  know  no 
absolute  method  of  purifying  the  metal.  Thus,  suppose  we  take 
an  alum  containing  0.1  per  cent,  of  iron  and  11  per  cent,  of 
alumina;  the  alumina  derived  from  it  will  contain  1  per  cent. 


REDUCTION    BY   POTASSIUM   OR   SODIUM. 


203 


of  iron,  and  supposing  the  alumina  to  give  up  all  the  aluminium 
in  it,  the  metal  will  be  contaminated  with  2  per  cent,  of  iron." 

"  Influence  of  flux  or  slag. — The  flux,  or  the  product  of  the 
reaction  of  the  sodium  on  the  aluminous  material,  ought  to  be 
volatile,  that  one  may  separate  the  aluminium  by  heat  from  the 
material  with  which  it  has  been  in  contact,  and  with  which  it 
remains  obstinately  impregnated  because  of  its  small  specific 
gravity." 

"  Influence  of  the  vessel. — The  siliceous  vessels  in  which  alu- 
minium is  received  or  melted  give  it  necessarily  a  large  quantity 
of  silicon,  a  very  injurious  impurity.  Silicon  cannot  be  separated 
from  aluminium  by  any  means,  and  the  siliceous  aluminium  seems 
to  have  a  greater  tendency  to  take  up  more  silicon  than  pure  alu- 
minium, so  that  after  a  small  number  of  remeltings  in  siliceous 
vessels  the  metal  becomes  so  impure  as  to  be  almost  infusible." 

In  order  to  avoid  the  dangers  pointed  out  above,  Deville  recom- 
mended following  scrupulously  the  following  details  in  order  to 
get  pure  aluminium. 

"  Reduction  by  solid  sodium. — The  crude  aluminium  chloride 
placed  in  the  cylinder  A  (Fig.  20),  is  vaporized  by  the  fire  and 

Fig.  20. 


passes  through  the  tube  to  the  cylinder  J5,  containing  60  to  80 
kilos  of  iron-nails  heated  to  a  dull-red  heat.  The  iron  retains 
as  relatively  fixed  ferrous  chloride,  the  ferric  chloride  and  hydro- 
chloric acid  which  contaminate  the  aluminium  chloride,  and  like- 
wise transforms  any  sulphur  dichloride  (SCI2)  in  it  into  ferrous 
chloride  and  sulphide  of  iron.  The  vapors  on  passing  out  of  B 
through  the  tube,  which  is  kept  at  about  300°,  deposit  spangles 
of  ferrous  chloride,  which  is  without  sensible  tension  at  that  tern- 


204  ALUMINIUM. 

perature.  The  vapors  then  enter  D,  a  cast-iron  cylinder  in  which 
are  three  cast-iron  boats  each  containing  500  grms.  of  sodium. 
It  is  sufficient  to  heat  this  cylinder  barely  to  a  dull-red  heat  in 
its  lower  part,  for  the  reaction  once  commenced  disengages  enough 
heat  to  complete  itself,  and  it  is  often  necessary  to  take  away  all 
the  fire  from  it.  There  is  at  first  produced  in  the  first  boat  some 
aluminium  and  some  sodium  chloride,  which  latter  combines  with 
the  excess  of  aluminium  chloride  to  form  the  volatile  aluminium- 
sodium  chloride,  Al2Cl6.2NaCl.  These  vapors  of  double  chloride 
condense  on  the  second  boat  and  are  decomposed  by  the  sodium  into 
aluminium  and  sodium  chloride.  A  similar  reaction  takes  place  in 
the  third  boat  when  all  the  sodium  of  the  second  has  disappeared. 
When  on  raising  the  cover  it  is  seen  that  the  sodium  of  the  last 
boat  is  entirely  transformed  into  a  lumpy  black  material,  and 
that  the  reactions  are  over,  the  boats  are  taken  out,  immediately 
replaced  by  others,  and  are  allowed  to  cool  covered  by  empty 
boats.  In  this  first  operation  the  reaction  is  rarely  complete,  for 
the  sodium  is  protected  by  the  layer  of  sodium  chloride  formed 
at  its  expense.  To  make  this  disappear,  the  contents  of  the 
boats  are  put  into  cast-iron  pots  or  earthen  crucibles,  which  are 
heated  until  the  aluminium  chloride  begins  to  volatilize,  when 
the  sodium  will  be  entirely  absorbed  and  the  aluminium  finally 
remains  in  contact  with  a  large  excess  of  its  chloride,  which  is 
indispensable  for  the  success  of  the  operation.  Then  the  pots  or 
crucibles  are  cooled,  and  there  is  taken  from  the  upper  part  of 
their  contents  a  layer  of  sodium  chloride  almost  pure,  while 
underneath  are  found  globules  of  aluminium  which  are  separated 
from  the  residue  by  washing  with  water.  Unfortunately,  the 
water  in  dissolving  the  aluminium  chloride  of  the  flux  exercises 
on  the  metal  a  very  rapid  destructive  action,  and  only  the  globules 
larger  than  the  head  of  a  pin  are  saved  from  this  washing.  These 
are  gathered  together,  dried,  melted  in  an  earthen  crucible,  and 
pressed  together  with  a  clay  rod.  The  button  is  then  cast  in  an 
ingot  mould.  It  is  important  in  this  operation  to  employ  only 
well  purified  sodium,  and  not  to  melt  the  aluminium  if  it  still 
contains  any  sodium,  for  in  this  case  the  metal  takes  fire  and  burns 
as  long  as  any  of  the  alkaline  metal  remains  in  it.  In  such  a 


REDUCTION   BY  POTASSIUM   OR  SODIUM.  205 

case  it  is  necessary  to  remelt  in  presence  of  a  little  aluminium- 
sodium  chloride. 

"  Such  is  the  detestable  process  by  means  of  which  were  made 
the  ingots  of  aluminium  sent  to  the  Exhibition  (1855).     To  com- 
plete my  dissatisfaction  at  the  process,  pressed  by  time  and  ignor- 
ant of  the  action  of  copper  on  aluminium,  I  employed  in  almost 
all  my  experiments  reaction  cylinders  and  boats  of  copper,  so 
that  the  aluminium  I  took  from  them  contained  such  quantities 
of  this  metal  as  to  form  a  veritable  alloy.     Moreover,  it  had  lost 
almost  all  ductility  and  malleability,  had  a  disagreeable  gray  tint, 
and  finally  at  the  end  of  two  months  it  tarnished  by  becoming 
covered  with  a  black  layer  of  oxide  or  sulphide  of  copper,  which 
could  only  be  removed  by  dipping  in  nitric  acid.     But,  singular 
to  relate,  an  ingot  of  virgin  silver  which  had  been  put  along- 
side the  aluminium  that  the  public  might  note  easily  the  dif- 
ference in  color  and  weight  of  the  two  metals,  was  blackened 
still  worse  than  the  impure  aluminium.     Only  one  of  the  bars 
exhibited,  which  contained  no  copper,  remained  unaltered  from 
the  day  of  its  manufacture  till  now  (1859).     It  was  some  of  this 
cupreous  aluminium  that  I  sent  to  Mr.  Regnault,  who  had  asked 
me  for  some  in  order  to  determine  its  specific  heat.     I  had  cau- 
tioned him  at  the  time,  of  the  number  and  nature  of  the  impuri- 
ties which   it   might  contain,  and  the  analysis  of  M.  Salvetat, 
which  is  cited  in  the  memoir  of  Regnault,  accords  with  the  mean 
composition  of  the  specimens  that  I  had  produced  and  analyzed 
at  that  time  (see  p.  54,  Analysis  1).     It  is  to  be  regretted  that  I 
gave  such  impure  material  to  serve  for  determinations  of  such 
splendid  precision ;  I  was  persuaded  to  do  so  only  by  the  entreaties 
of  M.  Regnault  who  could  not  wait  until  I  prepared  him  better. 
It  is  also  this  cupreous  aluminium  which  M.  Hulot  has  called 
t  hard  aluminium/  in  a  note  on  the  physical  properties  of  this 
metal  which  he  addressed  to  the  Academy.     Hulot  has  remarked 
that  this  impure  metal,  which  is  crystalline  in  structure,  after 
having  been  compressed  between  the  dies  of  the  coining  press 
may  lose  its  crystalline  structure,  to  which  it  owes  its  brittleness, 
and  become  very  malleable.     It  possesses  then  such  strength  that 
it  works  well  in  the  rolls  of  a  steel-rolling  mill.     Further,  this 


206  ALUMINIUM. 

'  hard  aluminium'  becomes  quite  unalterable  when  it  has  thus 
lost  its  texture." 

"  Reduction  by  sodium  vapor. — This  process,  which  I  have  not 
perfected,  is  very  easy  to  operate,  and  gave  me  very  pure  metal 
at  the  first  attempt.  I  operate  as  follows  :  I  fill  a  mercury  bot- 
tle with  a  mixture  of  chalk,  carbon,  and  carbonate  of  soda,  in 
the  proportions  best  for  generating  sodium.  An  iron  tube  about 
ten  centimetres  long  is  screwed  to  the  bottle,  and  the  whole  placed 
in  a  wind  furnace,  so  that  the  bottle  is  heated  to  red-white  and 
the  tube  is  red  to  its  end.  The  end  of  the  tube  is  then  intro- 
duced into  a  hole  made  in  a  large  earthen  crucible  about  one- 
fourth  way  from  the  bottom,  so  that  the  end  of  the  tube  just 
reaches  the  inside  surface  of  the  crucible.  The  carbonic  oxide 
(CO)  disengaged  burns  in  the  bottom  of  the  crucible,  heating  and 
drying  it ;  afterwards  the  sodium  flame  appears,  and  then  pieces 
of  aluminium  chloride  are  thrown  into  the  crucible  from  time  to 
time.  The  salt  volatilizes  and  decomposes  before  this  sort  of 
tuyere  from  which  issues  the  reducing  vapor.  More  aluminium 
salt  is  added  when  the  vapors  coming  from  the  crucible  cease  to 
be  acid,  and  when  the  flame  of  sodium  burning  in  the  atmosphere 
of  aluminium  chloride  loses  its  brightness.  When  the  operation 
is  finished,  the  crucible  is  broken  and  there  is  taken  from  the 
walls  below  the  entrance  of  the  tube  a  saline  mass  composed  of 
sodium  chloride,  a  considerable  quantity  of  globules  of  aluminium, 
and  some  sodium  carbonate,  which  latter  is  in  larger  quantity  the 
slower  the  operation  was  performed.  The  globules  are  detached 
by  plunging  the  saline  mass  into  water,  when  it  becomes  necessary 
to  notice  thp  reaction  of  the  water  on  litmus.  If  the  water  be- 
comes acid,  it  is  renewed  often  ;  if  alkaline,  the  mass  impregnated 
with  metal  must  be  digested  in  nitric  acid  diluted  with  three  or 
four  volumes  of  water,  and  so  the  metal  is  left  intact.  The 
globules  are  reunited  by  melting  with  the  precautions  before 
given." 

Deville's  Process  (1859). 

The  process  then  in  use  at  Nanterre  was  based  on  the  use  of 
aluminium-sodium  chloride,  which  was  reduced  by  sodium,  with 
cryolite  or  fluorspar  as  a  flux.  The  methods  of  preparing  each 


REDUCTION  BY   POTASSIUM  OR   SODIUM.  207 

of  these  materials  were  carefully  studied  out  at  the  chemical 
works  of  La  Glaciere,  where  from  April  1856,  to  April  1857, 
the  manufacture  of  aluminium  was  carried  on  by  a  company 
formed  by  Deville  and  a  few  friends,  and  from  thence  proceeded 
the  actual  system  which  was  established  at  Nanterre  under  the 
direction  of  M.  Paul  Morin  when  the  works  at  La  Glaciere  were 
closed.  The  methods  of  preparation  of  alumina,  aluminium- 
sodium  chloride  and  sodium  used  at  Nanterre  are  placed  under 
their  respective  headings  (pp.  120,  127,  161,  163). 

In  the  first  year  that  the  works  at  Nanterre  were  in  operation 
there  were  made 

Aluminium-sodium  chloride      ....     10,000  kilos. 

Sodium      ........       2,000     " 

Aluminium 600     " 

The  metal  prepared  improved  constantly  in  quality,  M.  Morin 
profiting  continually  by  his  experience  and  improving  the  prac- 
tical details  constantly,  so  that  the  aluminium  averaged,  in  1859, 
97  per  cent.  pure.  (See  Analysis  9,  p.  54.) 

As  to  the  rationale  of  the  process  used,  aluminium  chloride  was 
replaced  by  aluminium-sodium  chloride  because  the  latter  is  less 
deliquescent  and  less  difficult  of  preservation ;  but  the  small 
amount  of  moisture  absorbed  by  the  double  chloride  is  held  very 
energetically,  at  a  high  temperature  giving  rise  to  some  alumina, 
which  incloses  the  globules  of  metal  with  a  thin  coating,  and  so 
hinders  their  easy  reunion  to  a  button.  Deville  remarked  that 
the  presence  of  fluorides  facilitated  the  reunion  of  these  globules, 
which  fact  he  attributed  to  their  dissolving  the  thin  coat  of  alu- 
mina ;  so  that  the  employment  of  a  fluoride  as  a  flux  became 
necessary  to  overcome  the  effect  produced  primarily  by  the  alu- 
minium-sodium chloride  holding  moisture  so  energetically.  De- 
ville gives  the  following  account  of  the  development  of  these  im- 
provements :  "  The  facility  with  which  aluminium  unites  in 
fluorides  is  due  without  doubt  to  the  property  which  these  possess 
of  dissolving  the  alumina  on  the  surface  of  the  globules  at  the 
moment  of  their  formation,  and  which  the  sodium  is  unable  to 
reduce.  I  had  experienced  great  difficulty  by  obtaining  small 
quantities  of  metal  poorly  united,  when  I  reduced  the  aluminium- 


208  ALUMINIUM. 

sodium  chloride  by  sodium  ;  M.  Rammelsberg,  who  often  made 
the  same  attempts,  tells  me  he  has  had  a  like  experience.  But  I 
am  assured  by  a  scrupulous  analysis  that  the  quantity  of  metal 
reduced  by  the  sodium  is  exactly  that  which  theory  indicates, 
although  after  many  operations  there  is  found  only  a  gray  pow- 
der, resolving  itself  under  the  microscope  into  a  multitude  of 
small  globules.  The  fact  is  simply  that  aluminium-sodium  chlor- 
ide is  a  very  poor  flux  for  aluminium.  MM.  Morin,  Debray, 
and  myself  have  undertaken  to  correct  this  bad  effect  by  the  in- 
troduction of  a  solvent  for  the  alumina  into  the  saline  slag  which 
accompanies  the  aluminium  at  the  moment  of  its  formation.  At 
first,  we  found  it  an  improvement  to  condense  the  vapors  of  alu- 
minium chloride,  previously  purified  by  iron,  directly  in  sodium 
chloride,  placed  for  this  purpose  in  a  crucible  and  kept  at  a  red 
heat.  We  produced  in  this  way,  from  highly  colored  material,  a 
double  chloride  very  white  and  free  from  moisture,  and  furnish- 
ing on  reduction  a  metal  of  fine  appearance.  We  then  intro- 
duced fluorspar  (CaF2)  into  the  composition  of  the  mixture  to  be 
reduced,  and  we  obtained  good  results  with  the  following  propor- 
tions : — 

Aluminium-sodium  chloride  .         .         .  400  grammes. 

Sodium  chloride 200  " 

Calcium  fluoride 200  " 

Sodium  .         ,   ".     .         .         .         .        t.       75  to  80  " 

"The  double  chloride  ought  to  be  melted  and  heated  almost  to 
low  red  heat  at  the  moment  it  is  employed,  the  sodium  chloride 
calcined  and  at  a  red  heat  or  melted,  and  the  fluorspar  pulver- 
ized and  well  dried.  The  double  chloride,  sodium  chloride  and 
calcium  fluoride  are  mixed  and  alternated  in  layers  in  the  crucible 
with  sodium.  The  top  layer  is  of  the  mixture,  and  the  cover  is 
sodium  chloride.  Heat  gently,  at  first,  until  the  reaction  ends, 
and  then  to  a  heat  about  sufficient  to  melt  silver.  The  crucible, 
or  at  least  that  part  of  it  which  contains  the  mixture,  ought  to 
be  of  a  uniform  red  tint,  and  the  material  perfectly  liquid.  It  is 
stirred  a  long  time  and  cast  on  a  well  dried,  chalked  plate. 
There  flows  out  first  a  very  limpid  liquid,  colorless  and  very  fluid, 
then  a  gray  material,  a  little  more  pasty,  which  contains  alu- 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  209 

minium  in  little  grains,  and  is  set  aside,  and  finally  a  button  with 
small,  metallic  masses  which  of  themselves  ought  to  weigh  20 
grms.  if  the  operation  has  succeeded  well.  On  pulverizing  and 
sieving  the  gray  slag,  5  or  6  grms.  of  small  globules  are  ob- 
tained, which  may  be  pressed  together  by  an  earthen  rod  in  an 
ordinary  crucible  heated  to  redness.  The  globules  are  thus  re- 
united, and  when  a  sufficient  quantity  is  collected  the  metal  is 
cast  into  ingots.  In  a  well-conducted  operation,  75  grms.  of 
sodium  ought  to  give  a  button  of  20  grms.  and  5  grms.  in 
grains,  making  a  return  of  one  part  aluminium  from  three  of  sod- 
ium. Theory  indicates  one  to  two  and  a  half,  or  30  grms.  of 
aluminium  from  75  of  sodium.  But  all  the  efforts  which  have 
been  made  to  recover  from  the  insoluble  slag  the  4  or  5  grms. 
of  metal  not  united  but  easily  visible  with  a  glass,  have  been  so 
far  unsuccessful.  There  is,  without  doubt,  a  knack,  a  particular 
manipulation  on  which  depends  the  success  of  an  operation 
which  would  render  the  theoretical  amount  of  metal,  but  we 
lack  it  yet.  These  operations  take  place,  in  general,  with  more 
facility  on  a  large  scale,  so  that  we  may  consider  fluorspar  as  be- 
ing suitable  for  serving  in  the  manufacture  of  aluminium  in  cru- 
cibles. We  employed  very  pure  fluorspar,  and  our  metal  was 
quite  exempt  from  silicon.  It  is  true  that  we  took  a  precaution 
which  is  necessary  to  adopt  in  operations  of  this  kind ;  we 
plastered  our  crucibles  inside  with  a  layer  of  aluminous  paste, 
the  composition  of  which  has  been  given  in  '  Ann.  de  Chim.  et 
de  Phys.'  xlvi.  195.  This  paste  is  made  of  calcined  alumina 
and  an  aluminate  of  lime,  the  latter  obtained  by  heating  together 
equal  parts  of  chalk  and  alumina  to  a  high  heat.  By  taking 
about  four  parts  calcined  alumina  and  one  of  aluminate  of  lime 
well  pulverized  and  sieved,  moistening  with  a  little  water,  there 
is  obtained  a  paste  with  which  the  inside  of  an  earthen  crucible 
is  quickly  and  easily  coated.  The  paste  is  spread  evenly  with  a 
porcelain  spatula,  and  compressed  strongly  until  its  surface  has 
become  well  polished.  It  is  allowed  to  dry,  and  then  heated  to 
bright  redness  to  season  the  coating,  which  does  not  melt,  and 
protects  the  crucible  completely  against  the  action  of  the  aluminium 
and  fluorspar.  A  crucible  will  serve  several  times  in  succession 
provided  that  the  new  material  is  put  in  as  soon  as  the  previous 
14 


210  ALUMINIUM. 

charge  is  cast.  The  advantages  of  doing  this  are  that  the  mix- 
ture and  the  sodium  are  put  into  a  crucible  already  heated  up, 
and  so  lose  less  by  volatilization  because  the  heating  is  done 
more  quickly,  and  the  crucible  is  drier  than  if  a  new  one  had 
been  used  or  than  if  it  had  been  let  cool.  A  new  crucible 
should  be  heated  to  at  least  300°  or  400°  before  being  used. 
The  saline  slag  contains  a  large  quantity  of  calcium  chloride, 
which  can  be  washed  away  by  water,  and  an  insoluble  material 
from  which  aluminium  fluoride  can  be  volatilized. 

"Yet  the  operation  just  described,  which  was  a  great  improve- 
ment on  previous  ones,  requires  many  precautions  and  a  certain 
skill  of  manipulation  to  succeed  every  time.  But  nothing  is  more 
easy  or  simple  than  to  substitute  cryolite  for  the  fluorspar.  Then 
the  operation  is  much  easier.  The  amount  of  metal  produced  is 
not  much  larger,  although  the  button  often  weighs  22  grammes, 
yet  if  cryolite  can  only  be  obtained  in  abundance  in  a  continuous 
supply,  the  process  which  I  will  describe  will  become  most  eco- 
nomical. The  charge  is  made  up  as  before,  except  introducing 
cryolite  for  fluorspar.  In  one  of  our  operations  we  obtained, 
with  76  grms.  of  sodium,  a  button  weighing  22  grms.  and  4  grms. 
in  globules,  giving  a  yield  of  one  part  aluminium  to  two  and 
eight-tenths  parts  sodium,  which  is  very  near  to  that  indicated  by 
theory.  The  metal  obtained  was  of  excellent  quality.  However, 
it  contained  a  little  iron  coming  from  the  aluminium  chloride, 
which  had  not  been  purified  perfectly.  But  iron  does  not  injure 
the  properties  of  the  metal  as  copper  does ;  and,  save  a  little 
bluish  coloration,  it  does  not  alter  its  appearance  or  its  resistance 
to  physical  and  chemical  agencies. 

"  After  these  attempts  we  tried  performing  the  reduction  simply 
on  the  bed  of  a  reverberatory  furnace,  relying  on  the  immediate 
reaction  of  sodium  on  the  double  chloride  to  use  up  these  mate- 
rials before  they  could  be  perceptibly  wasted  by  the  furnace  gases. 
This  condition  was  realized  in  practice  with  unlooked-for  success. 
The  reduction  is  now  made  on  a  somewhat  considerable  scale  at 
the  Nanterre  works,  and  never,  since  commencing  to  operate  in 
this  way,  has  a  reduction  failed,  the  results  obtained  being  always 
uniform.  The  furnace  now  used  has  all  the  relative  dimensions 
of  a  soda  furnace.  In  fact,  almost  the  temperature  of  an  ordinary 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  211 

soda  furnace  is  required  that  the  operation  may  succeed  per- 
fectly. The  absolute  dimensions  of  the  furnace,  however,  may 
vary  with  the  quantity  of  aluminium  to  be  made  in  one  opera- 
tion, and  are  not  limited.  With  a  bed  of  one  square  metre  sur- 
face, 6  to  10  kilos  of  aluminium  can  be  reduced  at  once ;  and 
since  each  operation  lasts  about  four  hours  and  the  furnace  may 
be  recharged  immediately  after  emptying  it  of  the  materials  just 
treated,  it  is  seen  that,  with  so  small  a  bed,  60  to  100  kilos  of  alu- 
minium can  be  made  in  twenty-four  hours  without  any  difficulty. 
In  this  respect,  I  think  the  industrial  problem  perfectly  solved. 
The  proportions  which  we  employed  at  first  were — 

Aluminium-sodium  chloride  (crushed)  .         .     10  parts. 

Fluorspar       .         .         .         .         .         .         .  5      " 

Sodium  (in  ingots)         .         .         .         .         .  2      " 

"  As  aluminium  is  still  very  dear,  it  is  necessary  to  direct  great 
attention  to  the  return  from  the  materials  used,  and  on  this  point 
there  is  yet  much  progress  to  be  made.  We  ascertained  many 
times  that  the  return  was  always  a  little  better,  and  the  reunion 
of  the  metal  to  a  single  ingot  a  little  easier,  when  cryolite  was 
substituted  for  fluorspar,  the  price  of  the  former,  after  having 
been  high,  being  now  lowered  to  350  francs  per  tonne  (about  $75 
per  long  ton).  For  this  reason  we  can  now  use  cryolite  instead 
of  fluorspar,  and  in  the  same  proportions.  W^e  can  also  recover 
alumina  from  this  cryolite  by  treating  the  slags  (see  p.  119).  The 
double  chloride  and  pulverized  cryolite  are  now  mixed  with  the 
sodium  in  small  ingots,  and  the  mixture  thrown  on  to  the  bed  of 
the  heated-up  furnace.  The  dampers  are  then  shut,  to  prevent  as 
much  as  possible  access  of  air.  Very  soon  a  lively  reaction 
begins,  with  the  production  of  such  heat  that  the  brick  sides 
of  the  furnace,  as  well  as  the  materials  on  the  hearth,  are 
made  bright  red-hot.  At  this  heat  the  mixture  is  almost  com- 
pletely fused.  Then  it  is  necessary  to  open  the  damper  and  direct 
the  flame  on  the  bed  in  such  manner  as  to  heat  the  bath  equally 
all  over  and  unite  the  reduced  aluminium.  When  the  operation 
is  considered  ended,  a  casting  is  made  by  an  opening  in  the  back 
of  the  furnace  and  the  slag  is  received  in  cast-iron  pots.  At  the 
end  of  the  cast  the  aluminium  arrives  in  a  single  jet,  which  unites 


212  ALUMINIUM. 

into  a  single  lump  at  the  bottom  of  the  still-liquid  slag.  The 
gray  slag  flowing  out  last  should  be  pulverized  and  sieved,  to 
extract  the  divided  globules  of  aluminium,  200  to  300  grammes 
of  which  can  sometimes  be  extracted  from  one  kilo  of  gray  slag. 
The  pulverization  of  the  slag  is  in  all  cases  indispensable  in  its 
subsequent  treatment  for  extracting  its  alumina.  The  slag  is  of 
two  kinds,  one  fluid  and  light,  which  covered  the  bath,  and  is 
rich  in  sodium  chloride ;  the  other  less  fusible  and  pasty,  gray  in 
color,  which  is  more  dense  and  lies  in  contact  with  the  aluminium. 
The  coloring  material  producing  the  gray  ness  is  carbon,  coming 
either  from  the  sodium  or  from  the  oil  which  impregnated  it,  or 
finally  from  the  vapor  of  the  oil.  I  attribute  the  slight  pastiness 
of  this  slag  to  a  little  alumina  dissolved  by  the  fluorides.  This 
slag  contains  about — 

Sodium  chloride     .         .         .  .         .         .60  parts. 

Aluminium  fluoride       .         .         .         .         .         .     40      " 

and  on  washing  it  the  former  dissolves  while  the  latter  remains, 
mixed  with  a  little  cryolite  or  alumina.  This  is  the  alumina 
which  had  been  dissolved  or  retained  in  the  bath  of  fluoride.  It 
will  be  remarked  that  the  bath  of  slag  contains  no  other  fluoride 
than  aluminium  fluoride,  which  does  not  attack  earthen  crucibles 
or  siliceous  materials  in  general  except  at  a  very  high  tempera- 
ture. It  is  for  this  reason  that  the  hearth  and  other  parts  of  the 
furnace  resist  easily  a  fluoride  slag  containing  only  aluminium 
fluoride,  which  has  not  the  property  of  combining  with  silicon 
fluoride  at  the  expense  of  the  silica  of  the  bricks — as  sodium 
fluoride  does  in  like  circumstances.  In  our  operations,  cryo- 
lite is  used  only  as  a  flux.  In  the  process  of  reduction  based  on 
cryolite  alone,  the  sodium  fluoride  resulting  is,  on  the  contrary, 
very  dangerous  to  crucibles,  and  it  is  due  to  that  fact  especially 
that  the  aluminium  absorbs  a  large  quantity  of  silicon,  which 
always  happens  with  this  method.  In  fact,  it  is  well  known  that 
metallic  silicon  can  be  prepared  in  this  way  by  prolonging  the 
operation  a  little." 

Deville  closes  his  account  of  the  aluminium  industry  in  1859 
with  these  words :  "  Many  things  yet  remain  to  us  to  do,  and 
we  can  scarcely  say  now  that  we  know  the  true  qualities  of  the 


REDUCTION  BY  POTASSIUM  OR  SODIUM.  213 

substances  we  employ.  But  the  matter  is  so  new,  is  harassed 
with  so  many  difficulties  even  after  all  that  has  been  done,  that 
our  young  industry  may  hope  everything  from  the  future  when 
it  shall  have  acquired  experience.  I  ought  to  say,  however,  that 
the  aluminium  industry  is  now  at  such  a  point  that  if  the  uses 
of  the  metal  are  rapidly  extended  it  may  change  its  aspect  with 
great  rapidity.  One  may  ask  to-day  how  much  a  kilo  of  iron 
would  cost  if  a  works  made  only  60  to  100  kilos  of  it  a  month, 
if  large  apparatus  were  excluded  from  this  industry,  and  iron 
obtained  by  laboratory  processes  which  would  permit  it  to  be- 
come useful  only  by  tedious  after-treatment.  Such  will  not  be 
the  case  with  aluminium,  at  least  with  the  processes  just  described. 
In  fact,  in  all  I  undertook,  either  alone  or  with  my  friends,  I 
have  always  been  guided  by  this  thought — that  we  ought  to  adopt 
only  such  apparatus  as  is  susceptible  of  being  immediately  en- 
larged, and  to  use  only  materials  almost  as  common  as  clay  itself 
for  the  source  of  the  aluminium." 


The  Devitte  Process  (1882). 

The  process  just  described  reached  a  fair  degree  of  perfection 
at  Nanterre,  under  the  direction  of  M.  Paul  Morin.  Afterwards, 
some  of  the  chemical  operations  incidental  to  the  process  were  car- 
ried on  at  the  works  of  the  Chemical  Manufacturing  Company 
of  Alais  and  Carmargue,  at  Saliudres  (Gard),  owned  by  H.  Merle 
&  Co.  At  a  later  date  the  whole  manufacture  was  removed  to 
this  place,  while  the  Societe  Anonyme  de  1'Aluminium,  at  Nan- 
terre,  worked  up  the  metal  and  placed  it  on  the  market.  The 
Salindres  works,  about  1880,  went  under  the  management  of  A. 
R.  Pechiney  &  Co.,  and  under  the  personal  attention  of  M. 
Pechiney  the  Deville  process  has  reached  its  present  state  of  per- 
fection. The  following  account  is  taken  mostly  from  M.  Mar- 
gottet's  article  on  aluminium  in  Fremy's  Encyclopedic  Chimique. 

An  outline  of  the  process,  as  it  now  stands,  may  very  appro- 
priately be  given  at  this  place,  although  detailed  descriptions  of 
the  preliminary  processes  for  preparing  the  materials  for  reduc- 
tion are  given  under  the  appropriate  headings  (see  pp.  109,  127). 

The  primary  material  to  furnish  the  aluminium  is  beauxite. 


214  ALUMINIUM. 

To  obtain  the  metal  it  is  necessary  to  proceed  successively  through 
the  following  operations  :  — 

I.  Preparation  of  the  aluminate  of  soda,  and  solution  of  this 
salt  to  separate  it  from  the  ferric  oxide  contained  in  the  beauxite. 

II.  Precipitation  of  hydrated  alumina  from  the  aluminate  of 
soda  by  a  current  of  carbon  dioxide  ;  washing  the  precipitate. 

III.  Preparation  of  a  mixture  of  alumina,  carbon,  and  salt, 
drying  it,  and  then  treating  with  gaseous  chlorine  to  obtain  the 
double  chloride  of  aluminium  and  sodium. 

IV.  Lastly,  treatment  of  this  chloride  by  sodium  to  obtain 
aluminium. 

The  principal  chemical  reactions  on  which  this  process  rests 
are  the  following  :  — 

Formation  of  aluminate  of  soda  by  calcining  beauxite  with 
sodium  carbonate  — 


(AlFe)2Os.2H2O  +  3Na2CO3  =  Al2O3.3Na2O  4-  Fe2Os 
4-  2H20  4-  3C02. 

Formation  of  alumina  by  precipitating  the  aluminate  of  soda 
with  a  current  of  carbon  dioxide  — 

Al2O3.3]NTa2O  4-  3CO2  +  3H2O  =  A12O3.3H2O  4-  3Na2CO3. 

Formation  of  aluminium  sodium  chloride  by  the  action  of  chlor- 
ine on  a  mixture  of  alumina,  carbon,  and  sodium  chloride  — 

APO3  4-  30  +  2]NaCl  +  6C1  =  Al2Cl6.2NaCl  +  3CO. 
Reduction  of  this  double  chloride  by  sodium  — 

Al2Cl6.2NaCl  4-  6Na  =  2A1  4-  8NaCl. 

As  observed  before,  we  will  here  consider  only  the  last  opera- 
tion. The  advances  made  since  1859  are  mostly  in  matters  of 
detail,  which  every  one  knows  are  generally  the  most  important 
part  of  a  process;  and  so,  although  a  few  of  the  details  may  be 
repeated,  yet  we  think  it  best  not  to  break  the  continuity  of  this 
description  by  excising  those  few  sentences  which  are  nearly 
identical  in  the  two  accounts. 

The  difficulty  of  this  operation,  at  least  from  an  industrial 
point  of  view,  is  to  get  a  slag  fusible  enough  and  light  enough 
to  let  the  reduced  metal  easily  sink  through  it  and  unite.  This 


[REDUCTION   BY   POTASSIUM   OR   SODIUM. 


215 


result  has  been  reached  by  using  cryolite,  a  white  or  grayish 
mineral  originally  from  Greenland,  very  easy  to  melt,  formula 
APF6.6NaF.  This  material  forms  with  the  sodium  chloride  re- 
sulting from  the  reaction  a  very  fusible  slag,  in  the  midst  of  which 
the  aluminium  collects  well,  and  falls  to  the  bottom.  In  one 
operation  the  charge  is  now  composed  of — 

100  kilos     ......     Aluminium-sodium  chloride. 

45     " -Cryolite. 

35     " Sodium. 

The  double  chloride  and  cryolite  are  pulverized,  the  sodium, 
cut  into  small  pieces  a  little  larger  than  the  thumb,  is  divided 
into  three  equal  parts,  each  part  being  put  into  a  sheet-iron  bas- 
ket. The  mixture  of  double  chloride  and  cryolite,  being  pulver- 
ized, is  divided  into  four  equal  parts,  three  of  these  are  respectively 
put  in  each  basket  with  the  sodium,  the  fourth  being  placed  in  a 

Fig.  21. 


basket  by  itself.  The  reduction  furnace  (see  Fig.  21)  is  a  little 
furnace  of  refractory  brick,  with  an  inclined  hearth  and  a  vaulted 
roof.  This  furnace  is  strongly  braced  by  iron  tie-rods,  because 
of  the  concussions  caused  by  the  reaction.  The  flame  may  at  any 
given  moment  be  directed  into  a  flue  outside  of  the  hearth.  At 
the  back  part  of  the  furnace,  that  is  to  say,  on  that  side  towards 
which  the  bed  slopes,  is  a  little  brick  wall  which  is  built  up  for 
each  reduction  and  is  taken  away  in  operating  the  running  out  of 
the  metal  and  slag.  A  gutter  of  cast-iron  is  placed  immediately 


216  ALUMINIUM. 

in  front  of  the  wall  to  facilitate  running  out  the  materials.  All 
this  side  of  the  furnace  ought  to  be  opened  or  closed  at  pleasure 
by  means  of  a  damper.  Lastly,  there  is  an  opening  for  charging 
in  the  roof,  closed  by  a  lid.  At  the  time  of  an  operation  the 
furnace  should  be  heated  to  low  redness,  then  are  introduced  in 
rapid  succession  the  contents  of  the  three  baskets  containing 
sodium,  etc.,  and  lastly  the  fourth  containing  only  double  chloride 
and  no  sodium.  Then  all  the  openings  of  the  furnace  are  closed 
and  a  very  vivid  reaction  accompanied  by  dull  concussions  imme- 
diately takes  place.  At  the  end  of  fifteen  minutes,  the  action 
subsides,  the  dampers  are  opened,  and  the  heat  continued,  mean- 
while stirring  the  mass  from  time  to  time  with  an  iron  poker. 
At  the  end  of  three  hours  the  reduction  is  ended,  and  the  metal 
collects  at  the  bottom  of  the  liquid  bath.  Then  the  running  out 
is  proceeded  with  in  three  phases  :  First. — Running  off  the  upper 
part  of  the  bath,  which  consists  of  a  fluid  material  completely  free 
from  reduced  aluminium  and  constituting  the  white  slag.  To  run 
this  out  a  brick  is  taken  away  from  the  upper  course  of  the  little 
wall  which  terminates  the  hearth.  These  slags  are  received  in  an 
iron  wagon.  Second. — Running  out  the  aluminium.  This  is 
done  by  opening  a  small  orifice  left  in  the  bottom  of  the  brick 
wall,  which  was  temporarily  plugged  up.  The  liquid  metal  is 
received  in  a  cast-iron  melting  pot,  the  bottom  of  which  has  been 
previously  heated  to  redness.  This  aluminium  is  immediately 
cast  in  a  series  of  small  rectangular  cast-iron  moulds.  Third. — 
Running  out  of  the  rest  of  the  bath,  which  constitutes  the  gray 
slags.  These  were,  like  the  white  slags,  formed  by  the  sodium 
chloride  and  cryolite,  but  they  contain,  in  addition,  isolated  glob- 
ules of  aluminium.  To  run  these  out,  all  the  bricks  of  the  little 
wall  are  taken  away.  This  slag  is  received  in  the  same  melting 
pot  into  which  the  aluminium  was  run,  the  latter  having  been 
already  moulded.  Here  it  cools  gradually,  and  after  cooling  there 
are  always  found  at  the  bottom  of  the  pot  several  grains  of  metal. 
In  a  good  operation  there  are  taken  from  one  casting  10.5  kilos 
of  aluminium,  which  is  sold  directly  as  commercial  metal. 

The  following  data  as  to  the  expense  of  this  process  may  be 
very  appropriately  inserted  here,  giving  the  cost  at  Salindres  in 
1872,  in  which  year  3600  kilos  are  said  to  have  been  made. 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  217 

*Manufacture  of  one  kilo  of  aluminium. 

Sodium      .     .     .     3.44  kilos  @  11.32  fr.  per  kilo          =  38  fr.  90  cent. 
Aluminium-sodium 


chloride      .     .  10.04          "        2.48      "         "  =  24 

Cryolite    .     .     .     3.87          "      61.0        "      100  kilos  =    2 
Coal      ....  29.17          "        1.40      "  "          =0 

Wages    ....    1 
Costs  .    0 


90 
36 
41 

80 

88 


Total      .     .     .     .  69   "  25     " 

This  must  be  increased  ten  per  cent,  for  losses  and  other  ex- 
penses, making  the  cost  of  aluminium  80  fr.  per  kilo,  and  it  is 
sold  for  100.  ($9.00  per  Ib.) 

According  to  a  statement  in  the  '  Bull,  de  la  Soc.  de  ^Industrie 
Mine-rale/  ii.,  451,  made  in  1882,  Salindres  was  then  the  only 
place  in  which  aluminium  was  being  manfactured. 

Niewerttts  Process  (1883). 

This  method  can  be  regarded  as  little  more  than  a  suggestion, 
since  it  follows  exactly  the  lines  of  some  of  Deville's  earlier  ex- 
periments. Although  theoretically  very  advantageous,  yet  in 
practice  it  has  probably  been  found  far  inferior  in  point  of  yield 
of  metal  and  expense  to  the  ordinary  sodium  processes.  The 
patent  is  said  to  be  taken  out  in  the  United  States  and  other 
countries  in  the  name  of  H.  Niewerth,  of  Hanover,  and  is  thus 
summarized  : — 

fA  compound  of  aluminium,  with  chlorine  or  fluorine,  is 
brought  by  any  means  into  the  form  of  vapor,  and  conducted, 
strongly  heated,  into  contact  with  a  mixture  of  62  parts  sodium 
carbonate,  28  coal,  and  10  chalk,  which  is  also  in  a  highly  heated 
condition.  This  mixture  disengages  sodium,  which  reduces  the 
gaseous  chloride  or  fluoride  of  aluminium,  the  nascent  sodium 
being  the  reducing  agent.  In  place  of  the  above  mixture  other 
suitable  mixtures  which  generate  sodium  may  be  employed,  or 
mixtures  may  also  advantageously  be  used  from  which  potassium 
is  generated. 

*  A.  Wurtz,  Wagner's  Jaresb.,  1874,  vol.  xxi. 
f  Sci.  Am.  Suppl.,  Nov.  17,  1883. 


218  ALUMINIUM. 

Gadsden's  Patent  (1883). 

H.  A.  Gadsden,  of  London,  and  E.  Foote,*  of  New  York, 
were  granted  a  patent  based  on  the  principle  of  heating  in  a 
retort  sodium  carbonate  and  carbonaceous  matter,  or  any  suitable 
mixture  for  generating  sodium,  and  conducting  the  vapor  of 
sodium  produced  into  another  retort,  lined  with  carbon,  in  which 
aluminium  chloride,  or  aluminium-sodium  chloride  or  cryolite 
has  been  placed  and  heated.  The  second  English  patent  claims  to 
heat  a  mixture  which  will  generate  sodium,  in  one  retort,  and 
pass  chlorine  over  a  mixture  of  carbon  and  alumina,  thus  gen- 
erating aluminium  chloride,  in  another  retort,  and  then  mixing 
the  two  vapors  in  a  third  retort  or  reaction  chamber. 

Frishmuitis  Process  (1884). 

This  was  patented  in  the  United  States  in  1884  (U.  S.  Pat. 
308,152,  Nov.  1884).  In  what  the  originality  of  the  process 
consists,  in  view  of  Deville's  publications  and  even  in  view  of  the 
processes  just  mentioned,  we  cannot  see,  and  we  simply  acquiesce 
blindly  to  the  mysterious  penetration  of  our  Patent  Office  Board. 
However,  Col.  Frishmuth  himself  admits,  in  1887,  having  aban- 
doned the  sodium  process ;  it  is  therefore  probable  that  the  dif- 
ficulties of  the  method  did  not  permit  its  competing  with  the 
more  roundabout  but  more  easily-conducted  operation  with  solid 
sodium.  A  simple  transcript  of  the  claims  in  his  patent  will 
give  a  sufficiently  extended  idea  of  the  reactions  proposed  to  be 
used. 

1.  The  simultaneous  generation  of  sodium  vapor  and  a  vola- 
tile compound  of  aluminium  in  two  separate  vessels  or  retorts, 
and  mingling  the  vapors  thus  obtained  in  a  nascent  (!)  state  in  a 
third  vessel,  wherein  they  react  on  each  other. 

2.  The  sodium  vapor  is  produced  from  a  mixture  of  a  sodium 
compound  and  carbon,  or  some  other  reducing  agent ;  and  the 
aluminous  vapor  from  aluminous  material.- 

3.  The  simultaneous  generation  of  sodium  vapor  and  vapor  of 

*  English  patents  1995  and  4930  (1883)  ;  German  patent  27,572  (1884). 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  219 

aluminium  chloride  or  aluminium  fluoride ;  or  of  sodium  vapor 
and  aluminium-sodium  chloride. 

4.  Converting  the  aluminous  material  to  a  vapor  by  heating  it 
in  a  retort  with  sodium  chloride,  and  subjecting  it  at  the  same 
time  to  chlorine  gas ;  mingling  the  vapor  of  aluminium-sodium 
chloride  thus  obtained  with  vapor  simultaneously  generated  from 
sodium  carbonate  and  carbon. 

H.  von  Groudllierys  Improvement  (1885). 

This  suggestion  as  to  the  way  of  performing  the  reduction  by 
sodium  is  the  subject  of  the  English  patent  7858,  June  29,  1885. 
Dr.  Fischer  remarks  on  it,  in  i  Wagner's  Jahresbericht'  for  1885, 
that  "  it  is  apparently  wholly  worked  out  at  the  writing-table." 
The  patentee,  Hector  von  Grousillier,  Springe,  Hanover,  thus 
describes  his  invention  : — 

"  In  order  to  avoid  the  difficulties  ordinarily  met  with  in  the 
use  of  aluminium-sodium  chloride  to  obtain  aluminium,  I  raise 
the  volatilizing  point  of  aluminium  chloride  by  performing  its 
reduction,  either  chemically  or  electrolytically,  under  pressure  in 
a  strong,  hermetically-closed  vessel  lined  with  clay  or  magnesia 
and  provided  with  a  safety  valve." 

The  Deville-Castner  Process  (1886). 

This  latest  development  of  the  old  Deville  process  is  now 
operated  by  the  Aluminium  Company,  Limited,  at  their  large 
new  works  at  Oldbury,  near  Birmingham,  England.  The  plant 
covers  nearly  five  acres  of  ground,  and  adjoins  Chance  Bros/ 
large  chemical  works,  from  which  the  hydrochloric  acid  used  is 
obtained  and  the  waste  soda-liquors  returned,  by  means  of  large 
pipes  connecting  the  two  plants.  The  company  is  thus  in  posi- 
tion to  obtain  acid  and  dispose  of  its  by-products  to  very  good 
advantage.  The  principle  on  which  the  process  works  is  similar 
to  its  predecessor,  in  being  the  reduction  of  aluminium-sodium 
chloride  by  sodium,  but  it  improves  on  the  other  in  the  cheaper 
production  of  both  these  materials.  For  instance,  the  alumina 
used  is  obtained  and  converted  into  double  chloride  by  Mr.  Web- 


220  ALUMINIUM. 

ster's  processes,  by  which  it  is  probable  that  this  salt  does  not  cost 
over  3d.  per  Ib.  (see  p.  133),  as  against  12d.,  the  cost  at  Salindres  ; 
further,  by  Mr.  Castner's  sodium  process  it  is  acknowledged  that 
the  sodium  costs  only  about  9d.  per  Ib.,  as  against  48d,  or  $1,  as 
formerly.  Since  10  Ibs.  of  the  chloride  and  3  Ibs.  of  sodium  are 
required  to  produce  1  Ib.  of  aluminium,  the  average  saving  in 
these  two  items,  over  the  old  process,  is  somewhere  about  75  per 
cent. 

The  works  contain  a  sodium  building,  in  which  are  four  large 
sodium  furnaces,  each  capable  of  producing  over  500  Ibs.  of 
that  metal  in  twenty-four  hours ;  the  sodium  is  also  remelted  and 
stored  in  the  same  building  (see  p.  166).  The  double  chloride 
furnaces  are  in  a  building  250  feet  by  50  feet  wide,  there  being 
12  furnaces  each  containing  5  retorts.  The  total  output  of 
double  chloride  is  an  average  of  5000  Ibs.  per  day.  (See  p.  129.) 
Connected  with  this  building  is  a  chlorine  plant  of  the  largest 
size,  capable  of  supplying  about  a  ton  and  a  half  of  chlorine  a 
day.  In  a  separate  building  are  two  reverberatory  furnaces  in 
which  the  final  reduction  takes  place  and  the  aluminium  is  pro- 
duced. Besides  these,  there  are  a  rolling  mill,  wire  mill,  and 
foundry  on  the  grounds.  From  the  quantity  of  sodium  and 
double  chloride  produced,  we  can  see  that  the  works  can  produce 
about  500  Ibs.  of  aluminium  a  day  or  150,000  Ibs.  a  year,  with 
some  sodium  left  over  for  sale  or  other  purposes. 

The  mode  of  conducting  the  reduction  is  not  very  different 
from  that  practised  at  Salindres.  There  are  two  regenerative 
reverberatory  furnaces  used,  one  about  twice  as  large  as  the 
other.  The  larger  furnace  has  a  bed  about  six  feet  square,  slop- 
ing towards  the  front  of  the  furnace  through  which  are  several 
openings  at  different  heights.  The  charge  for  this  furnace  con- 
sists of  1200  Ibs.  of  double  chloride,  350  Ibs.  of  sodium,  and 
600  Ibs.  of  cryolite  for  a  flux.  The  chloride  is  in  small  pieces, 
the  cryolite  is  in  powder,  and  the  sodium  is  cut  into  thin  slices 
by  a  machine.  These  ingredients  are  put  into  a  revolving 
wooden  drum  placed  on  a  staging  over  the  furnace,  and  are  there 
thoroughly  mixed.  The  drum  is  then  opened  and  turned, 
when  the  contents  fall  into  a  small  wagon  beneath.  The  fur- 
nace having  been  raised  to  the  required  temperature,  all  the 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  221 

clampers  are  shut  and  the  car  is  moved  on  a  track  immediately 
over  a  large  hopper  placed  in  the  roof  of  the  furnace.  The  hop- 
per being  opened  the  charge  is  dumped  in  and  drops  on  to  the 
centre  of  the  hearth.  The  reaction  is  immediate  and  the  whole 
charge  becomes  liquid  in  a  very  short  time.  After  a  few 
minutes,  heating  gas  is  again  turned  on  and  the  furnace  kept 
moderately  hot  for  two  or  three  hours.  The  reaction  has  been 

Al2Cl6.2NaCl  +  6Na  =  Al2  +  SNaCl 

and  the  aluminium  gathers  under  the  bath  of  cryolite  and  sod- 
ium chloride.  One  of  the  lower  tap  holes  is  then  opened  with 
a  bar,  and  the  aluminium  run  out  into  moulds.  When  the 
metal  has  all  run  out  it  is  followed  by  slag,  which  flows  into  iron 
wagons.  The  openings  are  then  plugged  up  and  the  furnace  is 
ready  for  another  charge.  The  charge  given  produces  usually 
115  to  120  Ibs.  of  aluminium,  the  whole  operation  lasting  about 
4  hours.  The  large  furnace  could  thus  produce  840  Ibs.  in  24 
hours,  and  the  smaller  one  half  that  quantity.  The  first  portion 
of  metal  running  out  is  the  purest,  the  latter  portions  and 
especially  that  entangled  in  the  slag  on  the  hearth,  and  which 
has  to  be  scraped  out,  containing  more  foreign  substances.  This 
impure  metal  is  about  one-fourth  of  all  the  aluminium  in  the  charge. 

The  purity  of  the  metal  run  out  depends  directly  on  the  purity 
of  the  chloride  used.  If  the  double  chloride  contains  0.2  per 
cent,  of  iron  the  metal  produced  will  very  probably  contain  all  of 
it,  or  2  per  cent.  Using  the  double  chloride  purified  by  Mr. 
Castner's  new  method  (see  p.  132),  by  which  the  content  of  iron 
is  reduced  to  0.05  per  cent,  or  less,  aluminium  can  be  made  con- 
taining less  than  0.5  per  cent,  of  iron  and  from  99  to  99.5  per 
cent,  of  aluminium.  Professor  Roscoe  exhibited  at  one  of  his 
lectures  a  mass  of  metal  weighing  116  Ibs.,  being  one  single  run- 
ning from  the  furnace,  and  which  contained  only  0.3  per  cent, 
silicon  and  0.5  per  cent.  iron.  In  practice,  the  metal  from  8  or 
10  runnings  is  melted  dowrn  together  to  make  a  uniform  quality. 

Taking  the  figures  given,  it  appears  that  the  metal  run  out  rep- 
resents 70  per  cent,  of  the  aluminium  in  the  charge,  and  80  per 
cent,  of  the  weight  which  the  sodium  put  in  should  reduce,  but 
since  an  indeterminate  weight  is  sifted  and  picked  from  the  slag, 


222  ALUMINIUM. 

it  is  probable  that  the  utilization  of  the  materials  is  more  perfect 
than  the  above  percentages.  However,  this  seems  to  be  the  part 
of  the  old  Devi  lie  process  least  improved  upon  in  these  new 
works,  for  there  seems  to  be  plenty  of  room  for  improvement  in 
perfecting  the  utilization  of  materials  especially  in  regard  to  loss 
of  sodium  by  volatilization,  which  undoubtedly  takes  place  and 
which  can  possibly  be  altogether  prevented. 


CHAPTER.  X. 

REDUCTION  OF  ALUMINIUM  COMPOUNDS  BY  MEANS  OF 

POTASSIUM  OR  SODIUM  (continued). 

II. 

The  methods  based  on  the  reduction  of  cryolite  can  be  most 
conveniently  presented  in  chronological  order. 

Rose's  Experiments  (1855). 

We  will  here  give  H.  Rose's  entire  paper,  as  an  account  of 
this  eminent  chemist's  investigations  written  out  by  himself  with 
great  detail,  describing  failures  as  well  as  successes,  cannot  but 
be  of  value  to  all  interested  in  the  production  of  aluminium.* 

"  Since  the  discovery  of  aluminium  by  Wohler,  Deville  has  re- 
cently devised  the  means  of  procuring  the  metal  in  large,  solid 
masses,  in  which  condition  it  exhibits  properties  with  which  we 
were  previously  unacquainted  in  its  more  pulverulent  form  as 
procured  by  Wohler's  method.  While,  for  instance,  in  the  lat- 
ter state  it  burns  vividly  to  white  earthy  alumina  on  being  ignited, 
the  fused  globules  may  be  heated  to  redness  without  perceptibly 
oxidizing.  These  differences  may  be  ascribed  to  the  greater 
amount  of  division  on  the  one  hand  and  of  density  on  the  other. 

*•  Pogg.  Annalen,  Sept.  1855. 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  223 

According  to  Deville,  however,  Wohler's  metal  contains  platinum, 
by  which  he  explains  its  difficulty  of  fusion,  although  it  affords 
white  alumina  by  combustion.  Upon  the  publication  of  De- 
ville's  researches  I  also  tried  to  produce  aluminium  by  the  decom- 
position of  aluminium-sodium  chloride  by  means  of  sodium.  I 
did  not,  however,  obtain  satisfactory  results.  Moreover,  Prof. 
Rammelsberg,  who  followed  exactly  the  method  of  Deville,  ob- 
tained but  a  very  small  product,  and  found  it  very  difficult  to 
prevent  the  cracking  of  the  glass-tube  in  which  the  experiment 
was  conducted  by  the  action  of  the  vapor  of  sodium  on  aluminium 
chloride.  It  appeared  to  me  that  a  great  amount  of  time,  trouble, 
and  expense,  as  well  as  long  practice,  was  necessary  to  obtain 
even  small  quantities  of  this  remarkable  metal. 

"  The  employment  of  aluminium  chloride  and  its  compounds 
with  alkali  chlorides  is  particularly  inconvenient,  owing  to  their 
volatility,  deliquescence,  and  to  the  necessity  of  preventing  all  ac- 
cess of  air  during  their  treatment  with  sodium.  It  very  soon  oc- 
curred to  me  that  it  would  be  better  to  use  the  fluoride  of  alu- 
minium instead  of  the  chloride ;  or  rather  the  combination  of  the 
fluoride  with  alkaline  fluorides,  such  as  we  know  them  through 
the  investigations  of  Berzelius,  who  pointed  out  the  strong  affinity 
of  aluminium  fluoride  for  sodium  fluoride  and  potassium  fluoride, 
and  that  the  mineral  occurring  in  nature  under  the  name  of  Cryo- 
lite was  a  pure  compound  of  aluminium  fluoride  and  sodium 
fluoride. 

"  This  compound  is  as  well  fitted  for  the  preparation  of  alu- 
minium by  means  of  sodium  as  aluminium  chloride  or  aluminium 
sodium  chloride.  Moreover,  as  cryolite  is  not  volatile,  is  readily 
reduced  to  the  most  minute  state  of  division,  is  free  from  water 
and  does  not  attract  moisture  from  the  air,  it  affords  peculiar  ad- 
vantages over  the  above-mentioned  compounds.  In  fact,  I 
succeeded  with  much  less  trouble  in  preparing  aluminium  by 
exposing  cryolite  together  with  sodium  to  a  strong  red  heat  in  an 
iron  crucible,  than  by  using  aluminium  chloride  and  its  compounds. 
But  the  scarcity  of  cryolite  prevented  my  pursuing  the  experi- 
ments. In  consequence  of  receiving,  however,  from  Prof.  Krantz, 
of  Bonn,  a  considerable  quantity  of  the  purest  cryolite  at  a  very 


224  ALUMINIUM. 

moderate  price  ($2  per  kilo),  I  was  enabled  to  renew  the  investi- 
gation. 

"  I  was  particularly  stimulated  by  finding,  most  unexpectedly, 
that  cryolite  was  to  be  obtained  here  in  Berlin  commercially  at  an 
inconceivably  low  price.  Prof.  Krantz  had  already  informed  me 
that  cryolite  occurred  in  commerce  in  bulk,  but  could  not  learn 
where.  Shortly  after,  M.  Rudel,  the  manager  of  the  chemical 
works  of  H.  Kunheim,  gave  me  a  sample  of  a  coarse  white  powder 
large  quantities  of  which  were  brought  from  Greenland,  by  \vay 
of  Copenhagen,  to  Stettin,  under  the  name  of  mineral  soda,  and 
at  the  price  of  $3  per  centner.  Samples  had  been  sent  to  the 
soap  boilers,  and  a  soda-lye  had  been  extracted  from  it  by  means 
of  quicklime,  especially  adapted  to  the  preparation  of  many  kinds 
of  soap,  probably  from  its  containing  alumina.  It  is  a  fact,  that 
powdered  cryolite  is  completely  decomposed  by  quicklime  and 
water.  The  fluoride  of  lime  formed  contains  no  alumina,  which 
is  all  dissolved  by  the  caustic  soda  solution  ;  and  this,  on  its  side, 
is  free  from  fluorine,  or  only  contains  a  minute  trace.  I  found 
this  powder  to  be  of  equal  purity  to  that  received  from  Prof. 
Krantz.  It  dissolved  without  residue  in  hydrochloric  acid  (in 
platinum  vessels) ;  the  solution  evaporated  to  dryness  with  sul- 
phuric acid,  and  heated  till  excess  of  acid  was  dissipated,  gave  a 
residue  which  dissolved  completely  in  water,  with  the  aid  of  a 
little  hydrochloric  acid.  From  this  solution,  ammonia  precipi- 
tated a  considerable  quantity  of  alumina.  The  solution  filtered 
from  the  precipitate  furnished,  on  evaporation,  a  residue  of  sulphate 
of  soda,  free  from  potash.  Moreover,  the  powder  gave  the  well- 
known  reactions  of  fluorine  in  a  marked  degree.  This  powder 
was  cryolite  of  great  purity  :  therefore  the  coarse  powder  I  first 
obtained  was  not  the  form  in  which  it  was  originally  produced. 
It  is  now  obtainable  in  Berlin  in  great  masses  ;  for  the  prepara- 
tion of  aluminium  it  must,  however,  be  reduced  to  a  very  fine 
powder. 

"  In  my  experiments  on  the  preparation  of  aluminium,  which 
were  performed  in  company  with  M.  Weber,  and  with  his  most 
zealous  assistance,  I  made  use  of  small  iron  crucibles,  1J  inches 
high  and  If  inches  upper  diameter,  which  I  had  cast  here.  In 
these  I  placed  the  finely  divided  cryolite  between  thin  layers  of 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  225 

sodium,  pressed  it  down  tight,  covered  with  a  good  layer  of  potass- 
ium chloride  (KC1),  and  closed  the  crucible  with  a  well-fitting 
porcelain  cover.  I  found  potassium  chloride  the  most  advan- 
tageous flux  to  employ ;  it  has  the  lowest  specific  gravity  of  any 
which  could  be  used,  an  important  point  when  the  slight  density 
of  the  metal  is  taken  into  consideration.  It  also  increases  the 
fusibility  of  the  sodium  fluoride.  I  usually  employed  equal 
weights  of  cryolite  and  potassium  chloride,  and  for  every  five 
parts  of  cryolite  two  parts  of  sodium.  The  most  fitting  quantity 
for  the  crucible  was  found  to  be  ten  grammes  of  powdered  cryo- 
lite. The  whole  was  raised  to  a  strong  red  heat  by  means  of  a 
gas-air  blowpipe.  It  was  found  most  advantageous  to  maintain 
the  heat  for  about  half  an  hour,  and  not  longer,  the  crucible  being 
kept  closely  covered  the  whole  time  ;  the  contents  were  then 
found  to  be  well  fused.  When  quite  cold  the  melted  mass  is 
removed  from  the  crucible  by  means  of  a  spatula,  this  is  facilitated 
by  striking  the  outside  with  a  hammer.  The  crucible  may  be 
employed  several  times,  at  last  it  is  broken  by  the  hammer  blows. 
The  melted  mass  is  treated  with  water,  when  at  times  only  a  very 
minute  evolution  of  hydrogen  gas  is  observed,  which  has  the  same 
unpleasant  odor  as  the  gas  evolved  during  solution  of  iron  in 
hydrochloric  acid.  The  carbon  contained  in  this  gas  is  derived 
from  a  very  slight  trace  of  naphtha  adhering  to  the  sodium  after 
drying  it.  On  account  of  the  difficult  solubility  of  sodium  fluor- 
ide, the  mass  is  very  slowly  acted  on  by  water,  although  the 
insolubility  is  somewhat  diminished  by  the  presence  of  the  potass- 
ium chloride.  After  twelve  hours  the  mass*  is  softened  so  far 
that  it  may  be  removed  from  the  liquid  and  broken  down  in  a 
porcelain  mortar.  Large  globules  of  aluminium  are  then  discov- 
ered, weighing  from  0.3  to  0.4  or  even  0.5  grammes,  which  may 
be  separated  out.  The  smaller  globules  cannot  well  be  separated 
from  the  undecomposed  cryolite  and  the  alumina  always  produced 
by  washing,  owing  to  their  being  specifically  lighter  than  the 
latter.  The  whole  is  treated  with  nitric  acid  in  the  cold.  The 
alumina  is  not  dissolved  thereby,  but  the  little  globules  then  first 
assume  their  true  metallic  lustre.  They  are  dried  and  rubbed  on 
fine  silk  muslin  ;  the  finely  powdered,  undecomposed  cryolite  and 
alumina  pass  through,  while  the  globules  remain  on  the  gauze. 
15 


226  ALUMINIUM. 

The  mass  should  be  treated  in  a  platinum  or  silver  vessel,  a  por- 
celain vessel  would  be  powerfully  acted  on  by  the  sodium  fluoride. 
The  solution,  after  standing  till  clear,  may  be  evaporated  to  dry- 
ness  in  a  platinum  capsule,  in  order  to  obtain  the  sodium  fluoride, 
mixed    however   with   much    potassium  chloride.      The   small 
globules  may  be  united  by  fusion  in  a  small  well-covered  porcelain 
crucible,  under  a  layer  of  potassium  chloride.     They  cannot  be 
united  without  a  flux.     They  cannot  be  united  by  mere  fusion, 
like  globules  of  silver,  for  instance,  for  though  they  do  not  appear 
to  oxidize  on  ignition  in  the  air,  yet  they  become  coated  with  a 
scarcely  perceptible  film  of  oxide,  which  prevents  their  running 
together  into  a  mass.     This  fusion  with  potassium  chloride  is 
always  attended  with  a  loss  of  aluminium.     Buttons  weighing 
0.85  gramme  lost,  when  so  treated,  0.05  gramme.     The  potassium 
chloride  when  dissolved  in  water  left  a  small  quantity  of  alumina 
undissolved,  but  the  solution  contained  none.     Another  portion 
of  the  metal  had  undoubtedly  decomposed  the  potassium  chloride  ; 
and  a  portion  of  this  salt  and  aluminium  chloride  must  have  been 
volatilized  during   fusion   (other  metals,  as  copper  and    silver, 
behave  in  a  similar  manner — Pogg.   Ixviii.   287).     I  therefore 
followed   the  instructions  of  Deville,  and  melted   the  globules 
under  a  stratum  of   aluminium-sodium  chloride  in   a  covered 
porcelain  crucible.      The  salt  was   melted  first,   and   then  the 
globules  of  metal  added  to  the  melted  mass.     There  is  no  loss,  or 
a  very  trifling  one  of  a  few  milligrammes  of  metal,  by  this  pro- 
ceeding.    When  the  aluminium  is  fused  under  potassium  chloride 
its  surface  is  not  perfectly  smooth,  but  exhibits  minute  concavities  ; 
with  aluminium-sodium  chloride  this  is  not  the  case.     The  readi- 
est method  of  preparing  the  double  chloride  for  this  purpose  is 
by  placing  a  mixture  of  alumina  and  carbon  in  a  glass  tube,  as 
wide  as  possible,  and  inside  this  a  tube  of  less  diameter,  open  at 
both  ends,  and  containing  sodium  chloride.     If  the  spot  where 
the  mixture  is  placed  be  very  strongly  heated,  and  that  where  the 
sodium  chloride  is  situated,  more  moderately,  while  a  current  of 
chlorine  is  passed  through  the  tube,  the  vapor  of  aluminium 
chloride  is  so  eagerly  absorbed  by  the  sodium  chloride  that  none 
or  at  most  a  trace  is  deposited  in  any  other  part  of  the  tube.     If 
the  smaller  tube  be  weighed  before  the  operation,  the  amount 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  227 

absorbed  is  readily  determined.  It  is  not  uniformly  combined  with 
the  sodium  chloride,  for  that  part  which  is  nearest  to  the  mixture 
of  charcoal  and  alumina  will  be  found  to  have  absorbed  the  most. 
"  I  have  varied  in  many  ways  the  process  for  the  preparation 
of  aluminium,  but  in  the  end  have  returned  to  the  one  just  de- 
scribed. I  often  placed  the  sodium  in  the  bottom  of  the  crucible, 
the  powdered  cryolite  above  it,  and  the  potassium  chloride  above 
all.  On  proceeding  in  this  manner,  it  was  observed  that  much 
sodium  was  volatilized,  burning  with  a  strong  yellow  flame,  which 
never  occurred  when  it  was  cut  into  thin  slices  and  placed  in 
alternate  layers  with  the  cryolite,  in  which  case  the  process  goes 
on  quietly.  When  the  crucible  begins  to  get  red  hot,  the  tem- 
perature suddenly  rises,  owing  to  the  commencement  of  the  de- 
composition of  the  compound ;  no  lowering  of  the  temperature 
should  be  allowed,  but  the  heat  should  be  steadily  maintained,  not 
longer,  however,  than  half  an  hour.  By  prolonging  the  process 
a  loss  would  be  sustained,  owing  to  the  action  of  the  potassium 
chloride  on  the  aluminium.  Nor  does  the  size  of  the  globules 
increase  on  extending  the  time  even  to  two  hours  ;  this  effect  can 
only  be  produced  by  obtaining  the  highest  possible  temperature. 
If  the  process  be  stopped,  however,  after  five  or  ten  minutes  of 
very  strong  heat,  the  production  is  very  small,  as  the  metal  has 
not  had  sufficient  time  to  conglomerate  into  globules,  but  is  in  a 
pulverulent  form  and  burns  to  alumina  during  the  cooling  of  the 
crucible.  No  advantage  is  gained  by  mixing  the  cryolite  with  a 
portion  of  chloride  before  placing  it  between  the  layers  of  sodium, 
neither  did  I  increase  the  production  by  using  aluminium-sodium 
chloride  to  cover  the  mixture  instead  of  potassium  chloride.  I 
repeatedly  employed  decrepitated  sodium  chloride  as  a  flux  in  the 
absence  of  potassium  chloride,  without  remarking  any  important 
difference  in  the  amount  of  metal  produced,  although  a  higher 
temperature  is  in  this  case  required.  The  operations  may  also 
be  conducted  in  refractory  unglazed  crucibles  made  of  stoneware, 
and  of  the  same  dimensions,  although  they  do  not  resist  so  well 
the  action  of  the  sodium  fluoride  at  any  high  heats,  but  fuse  in 
one  or  more  places.  The  iron  crucibles  fuse,  however,  when 
exposed  to  a  very  high  temperature  in  a  charcoal  fire.  The  prod- 
uct of  metal  was  found  to  vary  very  much,  even  when  operating 


228  ALUMINIUM. 

exactly  in  the  manner  recommended  and  with  the  same  quantities 
of  materials.  I  never  succeeded  in  reducing  the  whole  amount 
of  metal  contained  in  the  cryolite  (which  contains  only  13  per 
cent  of  aluminium).  By  operating  on  10  grammes  of  cryolite, 
the  quantity  I  always  employed  in  the  small  iron  crucible,  the 
most  successful  result  was  0.8  grm.  But  0.6  or  even  0.4  grm. 
may  be  considered  favorable  ;  many  times  I  obtained  only  0.3 
grm.,  or  even  less.  These  very  different  results  depend  on  various 
causes,  more  particularly,  however,  on  the  degree  of  heat  obtained. 
The  greater  the  heat  the  greater  the  amount  of  large  globules, 
and  the  less  amount  of  minutely  divided  metal  to  oxidize  during 
the  cooling  of  the  crucible.  I  succeeded  once  or  twice  in  reducing 
nearly  the  whole  of  the  metal  to  one  single  button  weighing  0.5 
grm.,  at  a  very  high  heat  in  a  stoneware  crucible.  I  could  not 
always  obtain  the  same  heat  with  the  blowpipe,  as  it  depended  in 
some  degree  on  the  pressure  in  the  gasometer  in  the  gas-works, 
which  varies  at  different  hours  of  the  day.  The  following  experi- 
ment will  show  how  great  the  loss  of  metal  may  be  owing  to 
oxidation  during  the  slow  cooling  of  the  crucible  and  its  contents : 
In  a  large  iron  crucible  were  placed  35  grms.  of  cryolite  in  alter- 
nate layers  with  14  grms.  of  sodium  and  the  whole  covered  with 
a  thick  stratum  of  potassium  chloride.  The  crucible,  covered  by 
a  porcelain  cover,  was  placed  in  a  larger  earthen  one  also  covered, 
and  the  whole  exposed  to  a  good  heat  in  a  draft  furnace  for  one 
hour  and  cooled  as  slowly  as  possible.  The  product  in  this  case 
was  remarkably  small,  for  0.135  grm.  of  aluminium  was  all  that 
could  be  obtained  in  globules.  The  differences  in  the  amounts 
reduced  depend  also  in  some  degree  on  the  more  or  less  suc- 
cessful stratification  of  the  sodium  with  the  powdered  cryolite,  as 
much  of  the  latter  sometimes  escapes  decomposition.  The  greater 
the  amount  of  sodium  employed,  the  less  likely  is  this  to  be  the  case ; 
however,  owing  to  the  great  difference  in  their  prices,  I  never 
employed  more  than  4  grms.  of  sodium  to  10  grms.  of  cryolite. 
In  order  to  avoid  this  loss  by  oxidation  I  tried  another  method 
of  preparation  :  Twenty  grms.  of  cryolite  were  heated  intensely 
in  a  gun-barrel  in  a  current  of  hydrogen,  and  then  the  vapor  of 
8  grms.  of  sodium  passed  over  it.  This  was  effected  simply  by 
placing  the  sodium  in  a  little  iron  tray  in  a  part  of  the  gun-barrel 


REDUCTION   BY   POTASSIUM   OR   SODIUM.  229 

without  the  fire,  and  pushing  it  forward  when  the  cryolite  had 
attained  a  maximum  temperature.  The  operation  went  on  very 
well,  the  whole  being  allowed  to  cool  in  a  current  of  hydrogen. 
After  the  treatment  with  water,  in  which  the  sodium  fluoride  dis- 
solved very  slowly,  I  obtained  a  black  powder  consisting  for  the 
most  part  of  iron.  Its  solution  in  hydrochloric  acid  gave  small 
evidence  of  aluminium.  The  small  amounts  I  obtained,  how- 
ever, should  not  deter  others  from  making  these  experiments. 
These  are  the  results  of  first  experiments  on  which  I  have  not 
been  able  to  expend  much  time.  Now  that  cryolite  can  be  pro- 
cured at  so  moderate  a  price,  and  sodium  by  Deville's  improve- 
ments will  in  future  become  so  much  cheaper,  it  is  in  the  power 
of  every  chemist  to  engage  in  the  preparation  of  aluminium,  and  I 
have  no  doubt  that  in  a  short  time  methods  will  be  found  afford- 
ing a  much  more  profitable  result. 

"  To  conclude,  I  am  of  opinion  that  cryolite  is  the  best  adapted 
of  all  the  compounds  of  aluminium  for  the  preparation  of  this 
metal.  It  deserves  the  preference  over  aluminium-sodium  chlor- 
ide or  aluminium  chloride,  and  it  might  still  be  employed  with 
great  advantage  even  if  its  price  were  to  rise  considerably.  The 
attempts  at  preparing  aluminium  direct  from  alumina  have  as  yet 
been  unattended  with  success.  Potassium  and  sodium  appear 
only  to  reduce  metallic  oxides  when  the  potash  and  soda  produced 
are  capable  of  forming  compounds  with  a  portion  of  the  oxide 
remaining  as  such.  Pure  potash  and  soda,  with  whose  properties 
we  are  very  slightly  acquainted,  do  not  appear  to  be  formed  in 
this  case.  Since,  however,  alumina  combines  so  readily  with  the 
alkalies  to  form  aluminates,  one  would  be  inclined  to  believe 
that  the  reduction  of  alumina  by  the  alkali  metals  should  succeed. 
But  even  were  it  possible  to  obtain  the  metal  directly  from  alu- 
mina, it  is  very  probable  that  cryolite  would  long  be  preferred 
should  it  remain  at  a  moderate  price,  for  it  is  furnished  by  nature 
in  a  rare  state  of  purity,  and  the  aluminium  is  combined  in  it 
with  sodium  and  fluorine  only,  which  exercise  no  prejudicial  in- 
fluence on  the  properties  of  the  metal,  whereas  alumina  is  rarely 
found  in  nature  in  a  pure  state  and  in  a  dense,  compact  condition, 
and  to  prepare  it  on  a  large  scale,  freeing  it  from  those  substances 


230  ALUMINIUM. 

which  would  act  injuriously  on  the  properties  of  the  metal,  would 
be  attended  with  great  difficulty. 

"The  buttons  of  aluminium  which  I  have  prepared  are  so 
malleable  that  they  may  be  beaten  and  rolled  out  into  the  finest 
foil  without  cracking  on  the  edges.  They  have  a  strong  metallic 
lustre.  Some  small  pieces,  not  globular,  however,  were  found  in 
the  bottom  of  the  crucible,  and  occasionally  adhering  to  it,  which 
cracked  on  being  hammered,  and  were  different  in  color  and  lustre 
from  the  others.  They  were  evidently  not  so  pure  as  the  greater 
number  of  globules,  and  contained  iron.  On  sawing  through  a  large 
button  weighing  3.8  grammes,  it  could  readily  be  observed  that 
the  metal  for  about  half  a  line  from  the  exterior  was  brittle,  while 
in  the  interior  it  was  soft  and  malleable.  Sometimes  the  interior 
of  a  globule  contained  cavities.  With  Deville,  I  have  occasion- 
ally observed  aluminium  crystallized.  A  large  button  became 
striated  and  crystalline  on  cooling.  Deville  believes  he  has 
observed  regular  octahedra,  but  does  not  state  this  positively. 
According  to  my  brother's  examination,  the  crystals  do  not  belong 
to  any  of  the  regular  forms.  As  I  chanced  on  one  occasion  to 
attempt  the  fusion  of  a  large,  flattened-out  button  of  rather  im- 
pure aluminium,  without  a  flux,  I  observed  before  the  heat  was 
sufficient  to  fuse  the  mass,  small  globules  sweating  out  from  the 
surface.  The  impure  metal  being  less  fusible  than  pure  meta^ 
the  latter  expands  in  fusing  and  comes  to  the  surface." 

Experiments  of  Percy  and  Dick  (1855). 

After  the  publication  of  Rose's  results,  widespread  attention 
was  directed  toward  this  field,  and  it  was  discovered  that  some 
six  months  previously  Dr.  Percy,  in  England,  had  accomplished 
almost  similar  results,  and  had  even  shown  a  specimen  of  the 
metal  to  the  Royal  Institution,  but  with  the  singular  fact  of 
exciting  very  little  attention.  These  facts  are  stated  at  length  in 
the  following  paper  written  by  Allan  Dick,  Esq.,  which  appeared 
in  November,  1855,  two  months  after  the  publication  of  H. 
Rose's  paper  : — * 

*  Phil.  Mag.,  Nov.  1855. 


DEDUCTION   BY   POTASSIUM   OR   SODIUM.  231 

"  In  the  last  number  of  this  magazine  was  the  translation  of  a 
paper  by  H.  Rose,  of  Berlin,  describing  a  method  of  preparing 
aluminium  from  cryolite.  Previously,  at  the  suggestion  of  Dr. 
Percy,  I  had  made  some  experiments  on  the  same  subject  in  the 
metallurgical  laboratory  of  the  School  of  Mines,  and  as  the 
results  obtained  agree  very  closely  with  those  of  Mr.  Rose,  it  may 
be  interesting  to  give  a  short  account  of  them  now,  though  no 
detailed  description  was  published  at  the  time,  a  small  piece  of 
metal  prepared  from  cryolite  having  simply  been  shown  at  the 
weekly  meeting  of  the  Royal  Institution,  March  30,  1855,  accom- 
panied by  a  few  words  of  explanation  by  Faraday. 

"  Shortly  after  the  publication  of  Mr.  Deville's  process  for 
preparing  aluminium  from  aluminium  chloride,  I  tried  along  with 
Mr.  Smith  to  make  a  specimen  of  the  metal,  but  we  found  it 
much  more  difficult  to  do  than  Deville's  paper  had  led  us  to 
anticipate,  and  had  to  remain  contented  with  a  much  smaller  piece 
of  metal  than  we  had  hoped  to  obtain.  It  is,  however,  undoubt- 
edly only  a  matter  of  time,  skill,  and  expense  to  join  successful 
practice  with  the  details  given  by  Deville.  Whilst  making  these 
experiments,  Dr.  Percy  had  often  requested  us  to  try  whether 
cryolite  could  be  used  instead  of  the  chlorides,  but  some  time 
elapsed  before  wre  could  obtain  a  specimen  of  the  mineral.  The 
first  experiments  were  made  in  glass  tubes  sealed  at  one  end,  into 
which  alternate  layers  of  finely  powdered  cryolite  and  sodium  cut 
into  small  pieces  were  introduced,  and  covered  in  some  instances 
with  a  layer  of  cryolite,  in  others  by  sodium  chloride.  The  tube 
was  then  heated  over  a  gas  blowpipe  for  a  few  minutes  till  de- 
composition had  taken  place  and  the  product  was  melted.  When 
cold,  on  breaking  the  tube,  it  was  found  that  the  mass  was  full  of 
small  globules  of  aluminium,  but  owing  to  the  specific  gravity  of 
the  metal  and  flux  being  nearly  alike,  the  globules  had  not  col- 
lected into  a  button  at  the  bottom.  To  effect  this,  long-continued 
heat  would  be  required,  which  cannot  be  given  in  glass  tubes 
owing  to  the  powerful  action  of  the  melted  fluoride  on  them. 
To  obviate  this  difficulty,  a  platinum  crucible  was  lined  with 
magnesia  by  ramming  it  in  hard,  and  subsequently  cutting  out 
all  but  a  lining.  In  this,  alternate  layers  of  cryolite  and  sodium 
were  placed,  writh  a  thickish  layer  of  cryolite  on  top.  The  cruci- 


232  ALUMINIUM. 

ble  was  covered  with  a  tight-fitting  lid,  and  heated  to  redness  for 
about  half  an  hour  over  a  gas  blowpipe.  When  cold  it  was 
placed  in  water,  and  after  soaking  for  some  time  the  contents 
were  dug  out,  gently  crushed  in  a  mortar,  and  washed  by  decan- 
tation.  Two  or  three  globules  of  aluminium,  tolerably  large 
considering  the  size  of  the  experiment,  were  obtained  along  with 
a  large  number  of  very  small  ones.  The  larger  ones  were  melted 
together  under  potassium  chloride.  Some  experiments  made  in 
iron  crucibles  were  not  attended  with  the  same  success  as  those  of 
Rose,  no  globules  of  any  considerable  size  remained  in  the  melted 
fluorides ;  the  metal  seemed  to  alloy  on  the  sides  of  the  crucible, 
which  acquired  a  color  like  zinc.  It  is  possible  that  this  differ- 
ence may  have  arisen  from  using  a  higher  temperature  than  Rose, 
as  we  made  these  experiments  in  a  furnace,  not  over  the  blowpipe. 
Porcelain  and  clay  crucibles  were  also  tried,  but  laid  aside  after  a 
few  experiments,  owing  to  the  action  of  the  fluorides  upon  them, 
which  in  most  cases  was  sufficient  to  perforate  them  completely." 

Deville's  Methods  (1856-8). 

*  "  I  have  repeated  and  confirmed  all  the  experiments  of  Dr. 
Percy  and  H.  Rose,  using  the  specimens  of  cryolite  which  I 
obtained  from  London  through  the  kindness  of  MM.  Rose  and 
Hofmann.  I  have,  furthermore,  reduced  cryolite  mixed  with 
sodium  chloride  by  the  battery,  and  I  believe  that  this  will  be  an 
excellent  method  of  covering  with  aluminium  all  the  other  metals, 
copper  in  particular.  Anyhow,  its  fusibility  is  considerably  in- 
creased by  mixing  it  with  aluminium-sodium  chloride.  Cryolite 
is  a  double  fluoride  of  aluminium  and  sodium,  containing  13  per 
cent,  of  aluminium  and  having  the  formula  APF6.6NaF.  I  have 
verified  these  facts  myself  by  many  analyses. 

"In  reducing  the  cryolite  I  placed  the  finely-pulverized  mix- 
ture of  cryolite  and  sodium  chloride  in  alternate  layers  with 
sodium  in  a  porcelain  crucible.  The  uppermost  layer  is  of  pure 
cryolite,  covered  with  salt.  The  mixture  is  heated  just  to  com- 
plete fusion,  and,  after  stirring  with  a  -pipe-stem,  is  let  cool.  On 

*  Ann.  de  Chem.  et  de  Phys.  [3],  xlvi.  451. 


REDUCTION   BY   POTASSIUM   OB   SODIUM.  233 

breaking  the  crucible,  the  aluminium  is  often  found  united  in 
large  globules  easy  to  separate  from  the  mass.  The  metal  always 
contains  silicon,  which  increases  the  depth  of  its  natural  blue  tint 
and  hinders  the  whitening  of  metal  by  nitric  acid,  because  of  the 
insolubility  of  the  silicon  in  that  acid.  M.  Rose's  metal  is  very 
ferruginous.  I  have  verified  all  M.  Rose's  observations,  and  I 
agree  with  him  concerning  the  return  of  metal,  which  I  have 
always  found  very  small.  There  are  always  produced  in  these 
operations  brilliant  flames,  which  are  observed  in  the  scoria  float- 
ing on  the  aluminium,  and  which  are  due  to  gas  burning  and 
exhaling  a  very  marked  odor  of  phosphorus.  In  fact,  phosphoric 
acid  exists  in  cryolite,  as  one  may  find  by  treating  a  solution  of 
the  mineral  in  sulphuric  acid  with  molybdate  of  ammonia,  accord- 
ing to  H.  Rose's  reaction. 

"M.  Rose  has  recommended  iron  vessels  for  this  operation, 
because  of  the  rapidity  with  which  alkaline  fluorides  attack 
earthen  crucibles  and  so  introduce  considerable  silicon  into  the 
metal.  Unfortunately,  these  iron  crucibles  introduce  iron  into 
the  metal.  This  is  an  evil  inherent  in  this  method,  at  least  in  the 
present  state  of  the  industry.  The  inconveniences  of  this  method 
result  in  part  from  the  high  temperature  required  to  complete  the 
operation,  and  from  the  crucible  being  in  direct  contact  with  the 
fire,  by  which  its  sides  are  heated  hotter  than  the  metal  in  the 
crucible.  The  metal  itself,  placed  in  the  lower  part  of  the  fire, 
is  hotter  than  the  slag.  This,  according  to  my  observations,  is 
an  essentially  injurious  condition.  The  slag  ought  to  be  cool,  the 
metal  still  less  heated,  and  the  sides  of  the  vessel  where  the  fusion 
occurs  ought  to  be  as  cold  as  possible.  The  yield  from  cryolite, 
according  to  Rose's  and  my  own  observations,  is  also  very  small. 
M.  Rose  obtained  from  10  of  cryolite  and  4  of  sodium  about  0.5 
of  aluminium.  This  is  due  to  the  affinity  of  fluorine  for  alu- 
minium, which  must  be  very  strong  not  only  with  relation  to  its 
affinity  for  sodium  but  even  for  calcium,  and  this  affinity  appears 
to  increase  with  the  temperature,  as  was  found  in  my  laboratory. 
Cryolite  is  most  convenient  to  employ  as  a  flux  to  add  to  the 
mixture  which  is  fused,  especially  when  operating  on  a  small 
scale. 

"  The  argument  which  decided  the  company  at  Nanterre  not  to 


234  ALUMINIUM. 

adopt  the  method  of  manufacture  exclusively  from  cryolite  was 
the  report  of  M.  de  Chancourtois,  mining  engineer,  who  had  just 
returned  from  a  voyage  to  Greenland.  According  to  the  verbal 
statements  of  this  gentleman,  the  gite  at  Evigfcok  is  accessible  only 
during  a  very  short  interval  of  time  each  year,  and,  because  of 
the  ice  fields,  can  only  be  reached  then  by  a  steamboat.  The 
workmen  sent  from  Europe  to  blast  and  load  up  the  rock  have 
scarcely  one  or  two  months  of  work  possible.  The  local  work- 
men remain  almost  a  whole  year  deprived  of  all  communication 
with  the  rest  of  the  world,  without  fresh  provisions  or  fuel  other 
than  that  brought  from  Europe  in  the  short  interval  that  naviga- 
tion is  open.  The  deposit  itself,  which  is  scarcely  above  sea- 
level,  can  be  easily  worked  with  open  roof,  but  the  neighborhood 
of  the  sea  in  direct  contact  with  the  vein,  the  unorganized  man- 
ner of  working,  and  the  lack  of  care  in  keeping  separate  the 
metalliferous  portions  of  the  ore — all  combine  to  render  the 
mineral  very  costly  and  further  developments  underground  almost 
impossible. 

"  It  is  therefore  fortunate  that  cryolite  is  not  indispensable,  for 
no  one  would  wish  to  establish  an  industry  based  on  the  employ- 
ment of  a  material  which  is  of  uncertain  supply." 

Tissier  Bros.'  Method  (1857). 

The  process  adopted  in  the  works  at  Amfreville,  near  Rouen, 
directed  by  Tissier  Bros.,  is  essentially  that  described  by  Percy 
and  Rose.  The  method  of  operating  is  given  by  the  Tissier  Bros, 
themselves  in  their  book  as  follows  : — 

"  After  having  finely  powdered  the  cryolite,  it  is  mixed  with  a 
certain  quantity  of  sodium  chloride  (sea  salt),  then  placed  between 
layers  of  sodium  used  in  the  proportions  given  by  M.  Rose,  in 
large  refractory  crucibles.  These  are  heated  either  in  a  rever- 
beratory  furnace  or  in  a  wind  furnace  capable  of  giving  a  tempera- 
ture high  enough  to  melt  the  fluoride  of  sodium  produced  by  the 
reaction.  As  the  sodium  fluoride  requires  a  pretty  high  tempera- 
ture to  fuse  it,  the  heat  will  necessarily  be  higher  than  that  re- 
quired in  the  reduction  of  the  double  chloride  of  aluminium  and 
sodium.  When  the  contents  of  the  crucible  are  melted,  so  as  to 


REDUCTION   BY   POTASSIUM   OR  SODIUM.  235 

be  quite  liquid,  the  fusion  is  poured  into  cast-iron  pots  at  the 
bottom  of  which  the  aluminium  collects  in  one  or  several  lumps." 

Tissier  Bros,  claimed  the  following  advantages  for  the  use  of 
cryolite : — 

.  "  Cryolite  comes  to  us  of  a  purity  difficult  to  obtain  with  the 
double  chloride  of  aluminium  and  sodium,  to  which  it  exactly 
corresponds ;  and  since,  thanks  to  the  perfection  we  have  attained 
in  using  it,  the  return  of  aluminium  is  exactly  correspondent  to 
the  amount  of  sodium  used  in  reduction,  it  is  easily  seen  what 
immense  advantages  result  from  its  employment.  The  double 
chloride  deteriorates  in  the  air,  it  gives  rise  in  the  works  to  vapors 
more  or  less  deleterious  and  corrosive,  and  its  price  is  always  high. 
Cryolite  can  be  imported  into  France  at  a  price  so  low  that  we 
have  utilized  it  economically  for  making  commercial  carbonate 
of  soda;  it  remains  unaltered  in  the  air,  emits  no  deleterious 
vapors,  and  its  management  is  much  more  easy  than  that  of  the 
double  chloride.  Moreover,  on  comparing  the  residues  of  the 
two  methods  of  reduction,  the  manufacture  from  double  chloride 
leaves  sodium  chloride,  almost  without  value,  while  the  manu- 
facture from  cryolite  leaves  sodium  fluoride,  which  may  be  con- 
verted for  almost  nothing  into  caustic  soda  or  carbonate,  and  so 
completely  cancels  the  cost  of  the  cryolite  from  the  cost  of  the 
aluminium.  The  most  serious  objection  which  can  be  made  to 
using  cryolite  is  that  the  sources  of  the  mineral  being  up  to  the 
present  very  limited,  the  future  prospect  of  aluminium  lies  neces- 
sarily in  the  utilization  of  clays  and  their  transformation  into 
aluminium  chloride ;  but,  admitting  that  other  sources  of  cryolite 
may  not  be  discovered  hereafter,  the  abundance  of  those  which 
exist  in  Greenland  will  for  a  long  time  to  come  give  this  mineral 
the  preference  in  the  manufacture  of  aluminium." 

The  most  serious  difficulty  which  this  process  had  to  meet,  and 
which  it  could  not  overcome,  was  the  high  content  of  silicon  in 
the  metal  produced.  A  specimen  of  their  aluminium  made  in 
1859  contained  4.4  per  cent,  of  silicon  alone  (see  p.  54,  Analy- 
sis 7).*  The  firm  at  Rouen  went  out  of  business  about  1863  or 
1865,  I  am  unable  to  give  the  exact  date.  From  that  time 

*  The  analysis  should  read  0.8  iron  and  4.4  silicon,  not  0.8  silicon  and 
4.4  iron. 


236  ALUMINIUM. 

until  quite  recently,  it  has  been  considered  that  the  best  use  of 
cryolite  is  as  a  flux  in  the  preparation  of  aluminium  from  alu- 
minium-sodium chloride,  in  which  case  the  slag  is  not  sodium 
fluoride  but  aluminium  fluoride,  which  acts  but  slightly  on  the 
containing  vessel. 

WoMer>s  Modifications  (1856). 

"Wohler  suggested  the  following  modifications  of  Deville's  pro- 
cess of  reducing  cryolite  in  crucibles,  by  means  of  which  the 
reduction  can  be  performed  in  an  earthen  crucible  without  the 
metal  produced  taking  up  silicon. 

*  "  The  finely  pulverized  cryolite  is  mixed  with  an  equal  weight 
of  a  flux  containing  7  parts  sodium  chloride  to  9  parts  potassium 
chloride.  This  mixture  is  then  placed  in  alternate  layers  with 
sodium  in  the  crucible,  50  parts  of  the  mixture  to  10  of  sodium, 
and  heated  gradually  just  to  its  fusing  point.  The  metal  thus  ob- 
tained is  free  from  silicon,  but  only  one-third  of  the  aluminium  in 
the  cryolite  is  obtained."  In  spite  of  the  small  yield,  this  method 
was  used  for  some  time  by  Tissier  Bros. 

Gerhard's  Furnace  (1858). 

This  furnace  was  devised  for  the  reduction  of  aluminium  either 
from  aluminium-sodium  chloride  or  from  cryolite,  the  object  being 
to  prevent  loss  of  sodium  by  ignition.  It  was  invented  and 
patented  by  W.  F.  Gerhard.f  "  It  consists  of  a  reverberatory 
furnace  having  two  hearths,  or  of  two  crucibles,  or  of  two  rever- 
beratory furnaces,  placed  one  above  the  other  and  communicating 
by  an  iron  pipe.  In  the  lower  is  placed  a  mixture  of  sodium 
with  the  aluminium  compound,  and  in .  the  upper  a  stratum  of 
sodium  chloride,  or  of  a  mixture  of  this  salt  and  cryolite,  or  of 
the  slag  obtained  in  a  previous  operation.  This  charge,  when 
melted,  is  made  to  run  into  the  lower  furnace  in  quantity  suffi- 
cient to  completely  cover  the  mixture  contained  therein,  and  so  to 
protect  it  from  the  air.  The  mixture  thus  covered  is  reduced  as 
by  the  usual  operation." 

*  Ann.  der  Chem.  und  Pharm.  99,255. 
f  Eng.  Pat.  1858,  No.  2247. 


EEDUCTION   BY   POTASSIUM   OR  SODIUM.  237 

Whether  a  furnace  was  ever  put  up  and  operated  on  this  prin- 
ciple the  author  cannot  say.  It  is  possible  that  it  may  have  been 
used  in  the  English  manufactories  started  in  1859  and  1860  at 
Battersea  and  Newcastle-on-Tyne. 

Thompson  and  White's  Patent  (1887). 

*  J.  B.  Thompson  and  W.  White  recommend  heating  a  mixture 
of  3  parts  sodium  and  4  parts  of  cryolite  to  100°,  whereby  the 
sodium  becomes  pasty  and  the  whole  can  be  well  kneaded 
together  with  an  iron  spatula.  When  cold,  4  parts  of  aluminium 
chloride  are  added,  and  the  mixture  put  into  a  hopper  on  top  of 
a  well-heated  reverberatory  furnace,  with  a  cup-shaped  hearth. 
The  charge  is  dropped  into  the  furnace  and  the  reaction  takes 
place  at  once.  To  produce  alloys,  this  patent  claims  that  16 
parts  of  cryolite  are  mixed  with  5  parts  of  sodium,  the  metal  added 
before  reduction  and  the  mixture  treated  as  above,  by  which 
means  explosions  are  avoided.  The  preliminary  heating  to  100° 
is  effected  in  a  jacketed  cast-iron  pot  connected  with  a  circulating 
boiler. 

Hampers  Experiment  (1888). 

fDr.  W.  Hampe  failed  to  produce  aluminium  bronze  by  treat- 
ing cryolite  with  sodium  in  the  presence  of  copper.  A  mixture  of 

44  grammes  finely  divided  copper, 
15         "         sodium,  in  small  pieces, 
100         "        finely  powdered  cryolite, 

was  melted  rapidly  in  a  carbon-lined  crucible.  There  were  no 
sounds  given  out  such  as  usually  accompany  other  reductions  by 
sodium,  but  much  sodium  vapor  was  given  off.  The  copper  but- 
ton contained  only  traces  of  aluminium. 

Netto's  Process  (1887). 

Dr.  Curt  Netto,  of  Dresden,  patented  in  England  and  Germany, 
in  spring  and  autumn  of  1887,  processes  for  producing  sodium 

*  English  Patent  8427,  June  11,  1887. 
f  Chemiker  Zeitung  (Cothen),  xii.  p.  391. 


238  ALUMINIUM. 

and  potassium  and  methods  of  using  them  in  producing  alu- 
minium. His  experiments  were  made  in  conjunction  with  Dr. 
Salomon,  of  Essen,  and  the  fact  that  the  experimental  apparatus 
was  put  up  in  Krupp's  large  steel  works  at  Essen  gave  rise  to 
reports  that  the  latter  had  taken  up  the  manufacture  of  alu- 
minium by  some  new  and  very  successful  process,  intending  to 
use  it  for  alloys  in  making  cannon.* 

In  the  latter  part  of  1888  we  hear  of  the  formation  of  the 
Alliance  Aluminium  Co.  of  London,  England,  capitalized  at 
£500,000,  purposing  to  manufacture  potassium,  sodium  and 
aluminium,  and  owning  the  English,  French,  German,  and  Belgian 
patents  of  Dr.  Netto  for  the  production  of  those  metals,  also  the 
processes  of  a  Mr.  Cunningham  for  the  same  purpose,  also  a  pro- 
cess for  the  production  of  artificial  cryolite  by  the  regeneration  of 
slags  (provisionally  protected  by  its  inventor,  Mr.  Forster,  of  the 
Lonesome  Chemical  Works,  Streatham),  and,  lastly,  a  process 
invented  by  Drs.  Netto  and  Salomon  by  which  aluminium  can  be 
raised  to  the  highest  standards  of  purity  on  a  commercial  scale. 
A  note  accompanying  the  above  announcement  stated  that  the 
exhaustive  experiments  made  at  Essen  had  satisfactorily  demon- 
strated the  practicability  of  the  processes,  and  that  the  company 
had  already  contracted  with  the  cryolite  mines  of  Greenland  for 
all  the  cryolite  the  company  would  need. 

In  June,  1888,f  we  learn  that  the  Alliance  Aluminium  Com- 
pany had  in  operation  a  small  aluminium  plant  at  King's  Head 
Yard,  London,  E.  C.,  and  that  when  the  process  was  in  con- 
tinuous operation  the  cost  of  the  metal  was  set  down  at  6  shil- 
lings per  pound.  It  is  probable  that  the  metal  exhibited  in  the 
Paris  Exposition  of  1889  was  produced  at  this  place. 

In  April,  1889,J  it  was  stated  in  the  scientific  journals  that 
ten  acres  of  ground  had  been  leased  at  Hepburn  on  which  to 
produce  sodium  by  Capt.  Cunningham's  process.  The  sodium 
produced  is  to  be  sent  to  Wallsend  to  be  used  by  the  Alliance 
Aluminium  Company,  who  are  erecting  a  large  works  at  that 
place. 

*  American  Register,  Paris,  August,  1888. 
f  Engineering,  June  1,  1888. 
J  E.  and  M.  J.,  April  27,  1889. 


REDUCTION    BY   POTASSIUM   OR   SODIUM.  239 

As  for  Capt.  Cunningham's  sodium  processes,  they  are  ap- 
parently identical  with  Dr.  Netto's.  Cunningham's  aluminium 
process*  consists  in  melting  the  sodium  to  be  used  with  lead,  in 
order  to  facilitate  the  submerging  of  the  sodium  under  the  molten 
aluminium  salt.  The  alloy  is  cast  into  bars  and  added  piece  by 
piece  to  the  bath  of  molten  aluminium  salt  on  the  hearth  of  a 
reverberatory  furnace.  After  the  reaction  the  mixture  separates 
by  specific  gravity  into  lead,  containing  a  little  aluminium,  and 
aluminium  containing  a  little  lead,  the  slag  floating  on  top  of  all. 
Aluminium  is  known  to  have  so  small  an  attraction  for  lead  that 
this  result  becomes  possible. 

Dr.  Netto  recommends  several  processes,  the  one  used  at  Lon- 
don being  the  following  : — f 

One  hundred  parts  of  cryolite  and  30  to  100  parts  of  sintered 
sodium  chloride  are  melted  at  a  red  heat  in  a  well-covered  clay 
crucible.  (Another  arrangement,  and  apparently  a  better,  is  to 
melt  this  mixture  on  the  hearth  of  a  reverberatory  furnace  and 
to  tap  it  into  a  deep,  conical  ladle,  in  which  the  succeeding  opera- 
tions proceed  as  about  to  be  described.)  As  soon  as  the  bath  is 
well  fused,  35  parts  of  sodium  at  the  end  of  a  rod,  and  covered 
over  by  a  perforated  concave  plate,  is  quickly  pushed  down  to 
the  bottom  of  the  crucible.  The  plate  mentioned  fits  across  the 
whole  section  of  the  crucible  at  its  lower  part,  so  that  the  fusible, 
easily  volatile  sodium,  being  vaporized,  is  divided  into  very  fine 
streams  as  it  passes  upwards  through  the  bath,  and  is  all  utilized 
before  it  reaches  the  surface.  In  this  way  the  reaction  is  almost 
instantaneous,  and  the  contents  can  be  poured  out  at  once  into 
iron  pots,  where,  on  cooling,  the  metal  is  found  as  a  large  lump 
at  the  bottom. 

It  is  further  observed  that  to  avoid  explosions  on  introducing 
the  sodium  it  should  have  in  it  no  cavities  which  might  contain 
moisture  or  hydrocarbons.  In  consequence  of  the  reaction  being 
over  so  quickly,  and  the  heat  set  free  in  the  reduction,  the  syrupy 
fusion  becomes  thin  as  water,  and  the  aluminium  disseminated 
through  the  mass  collects  together  completely,  so  that  the  slag 

*  English  Patent,  16727,  Dec.  5,  1887. 

f  German  Patent  (D.  R.  P.)  45198,  March  26,  1887. 


240  ALUMINIUM. 

contains  no  particles  visible  to  the  eye.  Since  the  reduction, 
pouring,  and  cooling  take  place  so  quickly,  the  aluminium  is  not 
noticeably  redissolved  by  the  bath,  thus  insuring  a  high  return  of 
metal.  By  using  35  parts  of  sodium  to  100  parts  of  cryolite,  10 
parts  of  aluminium  are  obtained.  Since  the  cryolite  contains  1 3 
per  cent,  of  aluminium,  the  return  is  77  per  cent,  of  the  amount 
of  metal  in  the  cryolite ;  since  35  parts  of  sodium  should  theo- 
retically displace  14  parts  of  aluminium,  the  return  is  71  per  cent, 
of  the  amount 'which  the  sodium  should  produce.  Dr.  Netto 
claims  that  this  is  double  the  return  formerly  obtained  from  cryo- 
lite. The  metal  produced  is  said  to  be  from  98.5  to  99  per  cent, 
pure. 

The  apparatus  erected  at  Krupp's  works  at  Essen,  which  was 
described  by  the  newspapers  as  similar  to  a  Bessemer  converter, 
was  constructed  and  operated  as  follows :  A  large  iron  cylinder 
is  pivoted  at  the  centre  in  a  manner  similar  to  a  Bessemer  con- 
verter. Passing  through  the  centre  of  the  cylinder,  longitudi- 
nally, is  a  large  iron  tube  in  which  generator  gas  is  burnt  to  heat 
the  vessel.  To  heat  it  up,  it  is  placed  erect,  connection  made 
with  the  gas-main,  while  a  hood  above  connects  with  the  chimney. 
On  top  of  the  cylinder,  a  close  valve  communicates  with  the  in- 
terior, for  charging,  and  at  the  other  end  is  a  tap-hole.  The 
charge  of  cryolite  being  put  in,  the  flame  is  passed  through  the 
central,  tube  until  the  mineral  is  well  fused.  Then  solid  or 
melted  sodium  is  passed  in  at  the  top,  the  valve  is  screwed  tight, 
the  gas  shut  off,  and  the  whole  cylinder  is  rotated  several  times 
until  reduction  is  complete,  when  it  is  brought  upright,  the  tap- 
hole  opened  and  slag  and  metal  tapped  into  a  deep  iron  pot,  where 
they  separate  and  cool.  Aluminium  thus  made  could  not  but 
contain  much  iron,  even  up  to  14  per  cent.,  it  is  said,  which  would 
prevent  its  use  for  any  purpose  except  alloying  with  iron.  To 
procure  pure  aluminium,  the  vessel  would  have  to  be  properly 
fettled. 

Dr.  Netto  also  devised  an  arrangement  similar  to  Heaton's 
apparatus  for  making  steel.  It  consisted  of  a  large,  well-lined 
vessel  on  trunnions,  the  bottom  of  which  was  filled  to  a  certain 
depth  with  sodium,  then  a  perforated  aluminium  plate  placed 
like  a  false  bottom  over  it,  On  pouring  molten  cryolite  into  the 


SEDUCTION   BY   POTASSIUM   OR   SODIUM.  241 

vessel  the  aluminium  plate  prevented  the  sodium  from  rising 
en  masse  to  the  surface  of  the  cryolite.  After  the  reaction  was 
over,  the  vessel  was  tilted  and  the  slag  and  metal  poured  out  into 
iron  pots. 

The  modification  of  the  crucible  method  appears  to  be  the  most 
feasible  of  Netto's  processes,  and  is  probably  now  being  used  at 
Wallsend  by  the  Alliance  Aluminium  Company.  Outside  esti- 
mates of  the  cost  of  aluminium  to  this  company  place  it  at  $1.50 
to  $2  per  pound.  They  were  selling  in  the  latter  part  of  1889 
at  11,  13,  and  15  shillings  per  pound,  according  to  quality. 

III. 

There  is  only  one  patentee  claiming  particularly  the  reduction 
of  aluminium  fluoride  by  sodium — Ludwig  Grabau,  of  Hann- 
over, Germany.  His  patents  on  this  subject  are  immediately 
preceded  by  others  on  a  method  of  producing  the  aluminium 
fluoride  cheaply,  which  are  described  on  p.  139,  and  the  inventor 
is  at  present  engaged  on  a  process  which  will  furnish  him  with 
cheap  sodium.  Mr.  Alexander  Siemens  is  authority  for  the 
statement  that  a  plant  was  in  operation  in  the  Spring  of  1889,  in 
Hannover,  producing  aluminium  by  this  process  on  a  commercial 
scale.  The  principal  object  of  Mr.  Grabau's  endeavors  has  been 
to  produce  metal  of  a  very  high  degree  of  purity.  To  this  end 
every  precaution  is  taken  to  procure  pure  materials  and  to  pre- 
vent contamination  during  reduction.  We  will  quote  from  a 
paper  written  by  Mr.  Grabau*  and  also  from  his  patent  specifi- 
cations^ the  following  explanation  of  the  process : — 

"  The  purifying  of  impure  aluminium  is  accompanied  by  so 
many  difficulties  that  it  appears  almost  impossible.  It  is  there- 
fore of  the  greatest  importance  to  so  conduct  the  operation  that 
every  impurity  is  excluded  from  the  start.  Molten  aluminium 
compounds,  whether  a  flux  is  added  or  not,  attack  any  kind  of 
refractory  vessels  and  become  siliceous,  if  these  vessels  are  made 

*  Zeitschrift  fiir  angewandte  Chemie,  1889,  vol.  6. 

t  German  Pat.  (D.  R.  P.)  47031,  Nov.  15,  1887.     English  Pat.  15593,  Nov. 
14,   1887.     U.  S.  Patents  386704,  July  24,   1888  ;  and  400449,  April  2,  1889. 
16 


242  ALUMINIUM. 

of  chamotte  or  like  materials,  or  if  made  of  iron  they  become 
ferruginous.  These  impurities  are  reduced  in  the  further  pro- 
cesses and  pass  immediately  into  the  aluminium  as  iron,  silicon, 
etc.  Evidently  the  case  is  altered  if  an  aluminium  compound 
which  is  infusible  can  be  used  advantageously.  Aluminium  fluor- 
ide is  infusible  and  also  retains  its  pulverized  condition  when 
heated  up  to  the  temperature  needed  for  its  use  ;  it  can  therefore 
be  heated  in  a  vessel  of  any  kind  of  refractory  material  or  even 
in  a  metallic  retort  without  danger  of  taking  up  any  impurity. 

"  Further,  it  is  necessary  for  succeeding  in  producing  alu- 
minium that  the  reduced  metal  shall  unite  to  a  large  body  after 
the  reduction.  For  this  purpose  all  previous  processes  use  fluxes, 
and  usually  cryolite.  But  cryolite  is  impure  and  therefore  here 
is  a  source  of  many  of  the  impurities  in  commercial  aluminium. 
Dr.  K.  Kraut,  of  Hannover,  has  observed  that,  according  to  the 
recent  analyses  of  Fresenius  and  Hintz,  commercial  cryolite 
contains  0.80  to  1.39  per  cent,  of  silicon  and  0.11  to  0.88  per 
cent,  of  iron,  and  that  these  impurities  inter-penetrate  the  mineral 
in  such  a  manner  as  to  be  often  only  visible  under  the  micro- 
scope and  therefore  totally  impossible  of  removal  by  mechanical 
means.  It  is  thus  seen  that  the  avoidance  of  the  use  of  any  flux 
is  of  great  importance  as  far  as  producing  pure  metal  is  con- 
cerned, as  well  as  from  an  economic  standpoint. 

"  By  the  following  process  it  is  also  possible  to  reduce  alu- 
minium fluoride  by  sodium  without  the  vessel  in  which  reduction 
takes  place  being  attacked  either  by  the  aluminium-sodium  fluor- 
ide formed  or  by  the  reduced  aluminium.  For  this  purpose  the 
aluminium  fluoride  and  sodium  are  brought  together  in  such 
proportions  that  after  the  reaction  there  is  still  sufficient  alumin- 
ium fluoride  present  to  form  with  the  sodium  fluoride  resulting 
from  the  reaction  a  compound  having  the  composition  of  cryolite. 
The  reaction,  therefore,  will  be 

2APF6  +  6Na  =  ~2A1  +  APF6.6NaF. 


"  Using  these  proportions,  the  aluminium  fluoride  must  be  pre- 
viously warmed  up  to  about  600°,  in  order  that  when  it  is  show- 
ered down  upon  the  melted  sodium  the  reaction  may  commence 
without  further  application  of  heat.  The  aluminium  fluoride 


REDUCTION   BY   POTASSIUM   OR   SODIUM. 

Fig.  22. 


243 


244  ALUMINIUM. 

remains  granular  at  this  temperature  and  therefore  remains  on 
top  of  the  melted  sodium,  like  saw-dust  or  meal  upon  water,  and 
under  its  protection  the  reaction  proceeds  from  below  upwards — 
an  important  advantage  over  the  usual  method  of  pouring  molten 
aluminium  compounds  on  to  sodium,  in  which  the  lighter  sodium 
floats  to  the  top  and  burns  to  waste.  If  solid  sodium  is  used  in 
my  process  the  aluminium  fluoride  must  be  somewhat  hotter  on 
being  poured  into  the  reduction  vessel,  or  about  700°.  For 
carrying  out  the  process  the  reduction  vessel  must  be  artificially 
cooled,  so  as  to  form  a  lining  by  chilling  some  of  the  aluminium- 
sodium  chloride  formed  by  the  reaction,  on  the  inner  walls. 
This  lining  is  in  no  wise  further  attacked  by  the  contents  of  the 
vessel,  nor  can  it  evidently  supply  to  them  any  impurity. 

"  The  furnace  A  (Fig.  22)  with  grate  B  and  chimney  C  serves  for 
heating  the  iron  retorts  D  and  jE",  which  are  coated  with  chamotte 
and  protected  from  the  direct  action  of  the  flame  by  brick  work. 
The  vessel  D  serves  for  heating  the  aluminium  fluoride,  and  is 
provided  with  a  damper  or  sliding  valve  beneath.  The  sodium 
is  melted  in  E,  and  can  be  emptied  out  by  turning  the  cock  h. 
The  water-jacketed  reduction  vessel  is  mounted  on  trunnions  to 
facilitate  emptying  it.  The  retorts  are  first  heated  dark  red-hot, 
and  D  is  filled  with  the  convenient  quantity  of  aluminium  fluor- 
ide. When  this  has  become  red  hot,  as  is  shown  by  a  small 
quantity  of  white  vapor  issuing  from  it,  the  required  quantity  of 
sodium  is  put  into  E.  This  melts  very  quickly,  and  is  then  im- 
mediately run  into  the  reduction  vessel  by  opening  the  stop-cock 
h.  As  soon  as  it  is  transferred,  the  slide  at  the  base  of  the  retort 
D  is  pulled  out  and  the  whole  quantity  of  aluminium  fluoride 
falls  at  once  upon  the  sodium  and  the  reaction  begins.  As  be- 
fore remarked,  the  granular  form  of  the  aluminium  fluoride 
keeps  it  on  top  of  the  sodium,  so  that  the  latter  is  completely 
covered  during  the  whole  reaction.  This  prevents  almost  alto- 
gether any  waste  of  sodium  by  volatilization.  Dr.  K.  Kraut 
testifies  to  an  operation  which  he  witnessed  in  which  the  return 
showed  83  per  cent,  of  the  sodium  to  have  been  utilized.  An 
efficiency  in  this  respect  of  over  90  per  cent,  has  been  occasionally 
reached,  while  the  average  is  80  to  90.  Ad.  Wurtz  states  that 
the  average  of  several  years'  working  of  the  Deville  process 


REDUCTION   BY   POTASSIUM    OR   SODIUM.  245 

showed  only  74.3  per  cent,  of  the  quantity  of  aluminium  pro- 
duced which  the  sodium  used  could  have  given. 

"  During  the  reaction  a  very  high  temperature  is  developed,  so 
that  the  cryolite  formed  becomes  very  fluid  but  is  chilled  against 
the  sides  of  the  vessel  to  a  thickness  of  a  centimetre  or  more. 
This  crust  is  a  poor  conductor  of  heat,  and  is  neither  attacked 
by  the  fluid  cryolite  nor  by^he  aluminium.  In  consequence  of 
the  great  fluidity  of  the  bath,  it  is  possible  for  the  aluminium 
to  unite  into  a  body  without  the  use  of  any  flux.  The  reaction 
b.emg  over,  which  is  accomplished  with  the  above  proportions  of 
materials  in  a  few  sec'onds,  and  the  vessel  having  been  shaken 
briskly  backwards  and  forwards  a  few  times  to  facilitate  the 
settling  of  the  aluminium,  the  whole  is  turned  on  the  trunnions 
and  emptied  into  a  water-jacketed  iron  pot  where  it  cools.  The 
crust  of  cryolite  inside  the  reduction  vessel  is  left  there,  and  the 
apparatus  is  ready  for  another  operation." 

M.  Grabau,  in  a  private  communication  to  the  author,  sums  up 
the  advantages  of  his  process,  including  the  production  of  the 
aluminium  fluoride,  as  follows  : — 

1.  The  process  is  not  dependent  on  natural  cryolite,  which  is 
expensive,  impure  and  not  easily  purified. 

2.  The  raw  material — aluminium  sulphate — can  be  procured 
in  large  quantities  and  of  perfect  purity. 

3.  The  aluminium  fluoride  is  produced  by  a  wet  process,  which 
offers  no  difficulties  to  production  on  a  large  scale. 

4.  The  fluorspar  may  be  completely  freed  from  foreign  metals 
by  washing  with  dilute  acid ;  any  silica  present  is  not  injurious, 
as  it  remains  undissolved  in  the  residue  during  the  reactions. 

5.  The  cryolite  formed  in  each  reduction  contains  no  impuri- 
ties, and  an  excess  of  it  is  produced  which  can  be  sold. 

6.  The  reduction  of  aluminium  fluoride  by  my  method  gives  a 
utilization  of  80  to  90  per  cent,  of  the  sodium  used,  which  is 
much  more  than  can  be  obtained  by  other  processes. 

7.  Aluminium  fluoride  is  infusible,  and  can  therefore  be  heated 
in  a  vessel  of  any  refractory  material  without  taking  up  any 
impurities.     It  is  also  unchanged  in  the  air,  and  can  be  kept 
unsealed  for  any  length  of  time  without  deteriorating  in  the  least. 


246  ALUMINIUM. 

8.  No  flux  has  to  be  added  for  reduction,  the  use  of  impure 
flux  being  a  frequent  cause  of  impurity  of  the  metal. 

In  point  of  fact,  M.  Grabau  has  succeeded  in  producing  several 
hundred  pounds  of  aluminium  averaging  over  99  J  per  cent.  pure. 
Dr.  Kraut  reports  an  analysis  of  an  average  specimen  with  99.62 
per  cent,  of  aluminium  (see  Analysis  20,  p.  54),  and  metal  has  been 
made  as  pure  as  99.8  per  cent.,  a  jrtece  of  which  has  been  kindly 
forwarded  the  author  by  M.  Grabau,  and  I  freely  admit  it  to  be 
the  finest  specimen  of  aluminium  I  have  ever  seen.  If  M.  Gra- 
bau's  statement  that  he  can  produce  metal  of  this  purity  without 
difficulty  on  a  commercial  scale  and  at* a  price  low  enough  to 
compete  with  the  other  commercial  brands  be  realized,  we  will 
freely  accord  that  gentleman  the  prize — not  for  cheap,  but  for 
pure  aluminium ;  cheap  aluminium  is  yet  to  come. 


CHAPTER  XI. 

REDUCTION  OF  ALUMINIUM  COMPOUNDS  BY  THE  USE  OF 
ELECTRICITY. 

As  preliminary  to  the  presentation  of  the  various  electrolytic 
methods  which  have  been  proposed  or  used,  it  may  be  profitable 
to  review  briefly  the  principles  of  electro-metallurgy  as  they 
apply  to  the  decomposition  of  aluminium  compounds. 

The  atomic  weight  of  aluminium  being  27,  its  chemical  equiv- 
alent, or  the  weight  of  it  equal  in  combining  power  to  one  part 
of  hydrogen,  is  9.  Therefore  a  current  of  quantity  sufficient  to 
liberate  1  part  of  hydrogen  in  a  certain  time  would  produce  9 
parts  of  aluminium  in  the  same  time,  according  to  the  funda- 
mental law  of  electric  decomposition.  It  has  been  determined 
that  a  current  of  1  ampere  acting  for  one  second,  liberates 
0.00001035  grammes  of  hydrogen ;  therefore  it  will  produce  or 
set  free  from  combination  in  the  same  time,  0.00009315  grammes 
of  aluminium.  This  is  the  electro-chemical  equivalent  of  alu- 
minium. Now,  from  thermo-chemical  data  we  know  that  the 
amount  of  energy  required  to  set  free  a  certain  weight  of  alu- 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  247 

minium  will  vary  with  the  compound  from  which  it  is  produced  ; 
but  the  above  equivalent  is  independent  of  the  compound  decom- 
posed, therefore  there  must  be  some  varying  factor  connected 
with  the  quantity  of  the  current  to  account  for  the  different 
amounts  of  work  which  the  current  does  in  decomposing  dif- 
ferent compounds  of  the  same  element.  This  is  exactly  in 
accordance  with  the  principles  of  the  mechanical  or  thermal 
equivalent  of  the  electric  current,  for  the  statement  "a  current  of 
one  ampere/'  while  it  expresses  a  definite  quantity  of  electricity, 
yet  carries  no  idea  of  the  energy  represented  by  that  current  ; 
we  must  know  against  what  resistance  or  with  what  force  that 
quantity  is  moved,  and  then  we  can  calculate  its  mechanical  equiv- 
alent. Now,  a  current  of  1  ampere  flowing  against  a  resistance 
of  1  ohm,  or  in  other  words,  with  a  moving  force  or  intensity  of 
1  volt,  represents  a  quantity  of  energy  in  one  second  equal  to 
0.00024  calories  of  heat  or  to  0.1  kilogrammetres  of  work,  and 
is  therefore  nearly  T|~g-  of  a  horse  power.  Therefore  we  can  cal- 
culate the  theoretical  intensity  of  current  necessary  to  overcome 
the  affinities  of  any  aluminium  compound  for  which  we  know 
the  appropriate  thermal  data.  For  instance,  when  aluminium 

forms  its  chloride  (see  p.  190)    '  —^  =  5960  calories  are  de- 

veloped per  kilo  of  aluminium  combining;  consequently  the 
liberating  of  0.00009315  grammes  of  aluminium  (its  electro- 
chemical equivalent),  requires  the  expenditure  of  an  amount  of 
energy  equal  to  0.00009315  x  5.960  *•  0.000555  calories. 
Since  a  current  of  1  ampere  at  an  intensity  of  1  volt  represents  only 
0.00024  calories,  the  intensity  of  current  necessary  to  decompose 

aluminium  chloride  is  theoretically  =  2.3  volts.     In  a 

0.00024 

similar  manner  we  can  calculate  that  to  decompose  alumina  would 

,.      f          f  391600       0.00000009315 
require  an  electro-motive  force  ot  —  —  —  X  - 

o4 


2.8  volts.  These  data  would  apply  only  to  the  substances  named 
in  a  fused  anhydrous  state  ;  with  hyd  rated  aluminium  chloride 
in  solution,  a  far  greater  electro-motive  force  would  be  necessary. 
If  we  had  the  thermal  data  we  could  also  calculate  the  intensity 
of  current  necessary  to  decompose  the  sulphate,  nitrate,  acetate, 


248  ALUMINIUM. 

etc.,  in  aqueous  solution  ;  but,  failing  these,  we  can  reason  from 
analogy  that  it  would  be  several  volts  in  each  case. 

To  utilize  such  calculations,  we  must  bear  in  mind  exactly  what 
they  represent.  To  decompose  fused  aluminium  chloride,  for 
instance,  not  only  must  the  current  possess  an  intensity  of  2.3 
volts  but  it  must  in  addition  have  power  enough  above  this  to 
overcome  the  transfer  resistance  of  the  electrolyte ;  i.  e.,  to  force 
the  current  through  the  bath  from  one  pole  to  the  other.  So,  then, 
2.3  volts  would  be  the  absolute  minimum  of  intensity  which  would 
produce  decomposition,  and  the  actual  intensity  practically  re- 
quired would  be  greater  than  this,  varying  with  the  distance  of 
the  poles  apart  and  the  temperature  of  the  bath  as  far  as  it  affects 
the  conducting  power  of  the  electrolyte.  From  this  it  would 
immediately  follow  that  if  the  substance  to  be  decomposed  is  an 
absolute  non-conductor  of  electricity,  no  intensity  of  current  will 
be  able  to  decompose  it.  If,  on  the  other  hand,  the  substance  is  a 
conductor  and  the  poles  are  within  reasonable  distance,  a  current 
of  a  certain  intensity  will  always  produce  decomposition.  The 
objection  is  immediately  made  that  in  most  cases  no  metal  is  ob- 
tained at  all,  which  is  true  not  because  none  is  produced  but 
because  it  is  often  dissolved  by  secondary  actions  as  quickly  as  it 
is  produced.  I  need  but  refer  to  the  historic  explanation  of  the 
decomposition  of  caustic  soda  in  aqueous  solution,  although  we 
have  cases  hardly  parallel  to  this  in  which  the  electrolyte  itself 
dissolves  the  separated  metal. 

How  about  the  case  of  aqueous  solutions?  Water  requires  a 
minimum  electro-motive  force  of  1.5  volts  to  decompose  it,  and 
hence  a  prominent  electrician  remarked  of  a  compound  which 
theoretically  required  over  2  volts  that  its  decomposition  in  aque- 
ous solution  would  involve  the  decomposition  of  the  water  and 
therefore  was  impossible.  This  remark  is  only  partly  true ;  for, 
caustic  soda  requires  over  2  volts,  yet  if  mercury  is  present  to 
absorb  the  sodium  as  it  is  set  free  and  protect  it  from  the  water, 
we  will  obtain  sodium  while  the  water  is  decomposed  at  the  same 
time.  The  truth  seems  to  be  that  if  two  substances  are  present 
which  require  different  electro-motive  force  to  decompose  them,  a 
current  of  a  certain  intensity  will  decompose  the  one  requiring 
least  force  without  affecting  the  other  at  all ;  but,  if  it  is  of  an 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  249 

intensity  sufficient  to  decompose  the  higher  compound,  then  the 
current  will  be  divided  in  some  ratio  between  the  two,  decompos- 
ing them  both.  This  theory  would  render  theoretically  possible 
the  decomposition  of  aluminium  salts  in  aqueous  solution,  with  a 
waste  of  power  proportional  to  the  amount  of  water  decomposed 
at  the  same  time  ;  but  whether  any  aluminium  would  be  obtained 
would  be  contingent  on  the  secondary  action  of  the  water  on  the 
aluminium.  Pure  aluminium  in  mass  is  not  acted  on  by  water, 
but  the  foil  is  rapidly  eaten  away  by  boiling  water.  The  state  of 
division  of  the  metal,  then,  determines  the  action  of  water  on  it, 
and  it  is  altogether  probable  that  the  reason  why  aluminium  has 
not  been  easily  and  beyond  question  deposited  from  aqueous  solu- 
tion is  that,  like  sodium,  it  is  attacked  as  soon  as  isolated,  the 
acidity  of  the  solution  converting  the  hydrate  formed  back  into 
the  salt,  or  else  simply  the  hydrate  remaining.  Unfortunately, 
mercury  does  not  exercise  the  same  function  with  aluminium  as 
with  sodium,  for  water  attacks  its  amalgam  with  aluminium,  and 
so  destroys  the  metal.  It  is  possible  that  if  some  analogous  sol- 
vent could  be  found  which  protected  the  aluminium  from  the 
action  of  water,  the  deposition  from  aqueous  solution  could 
be  made  immediately  successful.  Perhaps  some  of  the  devices 
about  to  be  described  have  successfully  overcome  these  difficulties, 
but  if  so  the  proof  of  this  has  never  been  verified  by  any  good 
authority,  nor  has  the  author  seen  any  so-called  aluminium 
plating  (from  aqueous  solution)  which  really  was  so. 

Further  remarks  as  to  the  amount  of  aluminium  theoretically 
obtainable  per  horse- power,  etc.  etc.,  will  come  up  in  connection 
with  the  various  processes. 

The  consideration  of  these  processes  falls  naturally  under  two 
heads : — 

I.  Deposition  from  aqueous  solution. 

II.  Decomposition  of  fused  aluminium  compounds. 

I. 

DEPOSITION  OF  ALUMINIUM  FROM  AQUEOUS  SOLUTION. 

The  status  of  this  question  is  one  of  the  curiosities  of  electro- 
metallurgic  science.  Evidently  attracted  by  the  great  reward  to  be 


250  ALUMINIUM. 

earned  by  success,  many  experimenters  have  labored  in  this  field, 
have  recommended  all  sorts  of  processes,  and  patented  all  kinds 
of  methods.  We  have  inventors  affirming  in  the  strongest  manner 
the  successful  working  of  their  methods,  while  other  experimenters 
have  followed  these  recipes,  and  tried  almost  every  conceivable 
arrangement,  yet  report  negative  results.  To  show  that  it  is  quite 
possible  that  many  strong  affirmations  may  be  made  in  good  faith, 
I  have  only  to  mention  the  fact  that  in  March,  1863,  Mr.  George 
Gore  described  in  the  Philosophical  Magazine  some  experiments 
by  which  he  deposited  coatings  of  aluminium  from  aqueous  solu- 
tions, and  afterwards,  in  his  text  book  of  Electro-metallurgy, 
asserts  that  he  knows  of  no  successful  method  of  doing  this  thing. 
Mr.  Gore  found  that  he  was  in  error  the  first  time  and  was  manly 
enough  to  acknowledge  it.  So,  if  we  take  the  position  of  many 
eminent  authorities  that  aluminium  cannot  by  any  methods  so  far 
advanced  be  deposited  from  aqueous  solution,  we  will  have  to 
admit  that  the  proposers  of  the  following  processes  are  probably 
misled  by  their  enthusiasm  in  affirming  so  strongly  that  they  can 
do  this  thing.  Yet  the  problem  is  not  impossible  of  solution, 
and  I  will  simply  assert  again  my  previous  statement,  that  no 
good  authority  testifies  to  the  success  of  any  process  so  far  ad- 
vanced, neither  have  I  seen  any  so-called  aluminium  plating 
(from  aqueous  solution)  which  really  was  aluminium. 

Messrs.  Thomas  and  Tilly*  coat  metals  with  aluminium  and 
its  alloys  by  using  a  galvanic  current  and  a  solution  of  freshly 
precipitated  alumina  dissolved  in  boiling  water  containing  potass- 
ium cyanide,  or  a  solution  of  freshly  calcined  alum  in  aqueous 
potassium  cyanide ;  also  from  several  other  liquids.  Their  patent 
covers  the  deposition  of  the  alloys  of  aluminium  with  silver, 
tin,  copper,  iron,  silver  and  copper,  silver  and  tin,  etc.  etc.,  the 
positive  electrode  being  of  this  metal  or  alloy. 

M.  Corbelli,  of  Florence,  f  deposits  aluminium  by  electrolyzing 
a  mixture  of  rock  alum  or  sulphate  of  alumina  (2  parts)  with 
calcium  chloride  or  sodium  chloride  (1  part)  in  aqueous  solution 
(7  parts),  the  anode  being  mercury  placed  at  the  bottom  of  the 

*  English  Patent,  1855,  No.  2756. 
f  English  Patent,  1858,  No.  507. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  251 

solution  and  connected  to  the  battery  by  an  iron  wire  coated  with 
insulating  material  and  dipping  its  uncovered  end  into  the  mer- 
cury. The  zinc  cathode  is  immersed  in  the  solution.  Aluminium 
is  deposited  on  the  zinc,  as  a  blackish  powder  or  as  a  thin,  com- 
pact sheet,  and  the  chlorine  which  is  liberated  at  the  anode  unites 
with  the  mercury,  forming  calomel. 

J.  B.  Thompson*  reports  that  he  has  for  over  two  years  been 
depositing  aluminium  on  iron,  steel,  and  other  metals,  and  driving 
it  into  their  surfaces  at  a  heat  of  500°  F.,  and  also  depositing 
aluminium  bronze  of  various  tints,  but  declines  to  state  his 
process. 

George  Gore,f  the  noted  electrician,  recommended  the  following 
procedure  for  depositing  aluminium  on  copper,  brass,  or  Ger- 
man silver : — 

"  Take  equal  measures  of  sulphuric  acid  and  water,  or  one  part 
sulphuric  acid,  one  part  hydrochloric  acid  and  two  parts  of  wrater, 
put  into  it  half  an  ounce  of  pipe  clay  to  the  pint  of  dilute  acid  and 
boil  for  an  hour.  Take  the  clear,  hot  liquid  and  immerse  in  it 
an  earthen  porous  cell  containing  sulphuric  acid  diluted  with 
ten  times  its  bulk  of  water,  together  with  a  rod  or  plate  of  amal- 
gamated zinc.  Connect  the  zinc  with  the  positive  wire  of  a 
Smee  battery  of  three  or  four  elements  connected  for  intensity. 
The  article  to  be  coated,  well  cleaned,  is  connected  with  the  nega- 
tive pole  and  immersed  in  the  hot  clay  solution.  In  a  few  min- 
utes a  fine,  white  deposit  of  aluminium  will  appear  all  over  its 
surface.  It  may  then  be  taken  out,  washed  quickly  in  clean 
water,  wiped  dry,  and  polished.  If  a  thicker  coating  is  required, 
it  must  be  taken  out  as  soon  as  the  deposit  becomes  dull,  washed, 
dried,  polished,  and  re-immersed,  and  this  must  be  repeated  at 
intervals  as  often  as  it  becomes  dull,  until  the  required  thickness 
is  obtained.  It  is  necessary  to  have  the  acid  well  saturated  by 
boiling,  or  no  deposit  will  be  obtained." 

Mierzinski  asserts  that  Dr.  Gore  was  mistaken  when  he  sup- 
posed this  deposit  to  be  aluminium,  and  in  Gore's  Text  Book  of 
Electro-metallurgy  no  mention  is  made  of  these  experiments,  the 

*  Chem.  News,  xxiv.  194  (1871). 

f  Philosophical  Magazine,  March,  1863. 


252  ALUMINIUM. 

author  thereby  acknowledging  the  error.  As  to  what  the  deposit 
could  have  been,  we  are  left  to  conjecture,  since  no  explanation 
has  been  advanced  by  Dr.  Gore ;  it  may  possibly  have  been  sili- 
con, mercury,  or  zinc,  as  all  three  of  these  were  present  besides 
aluminium. 

J.  A.  Jeancon*  has  patented  a  process  for  depositing  alumin- 
ium from  an  aqueous  solution  of  a  double  salt  of  aluminium  and 
potassium  of  specific  gravity  1.161 ;  or  from  any  solution  of  an 
aluminium  salt,  such  as  sulphate,  nitrate,  cyanide,  etc.,  concen- 
trated to  20°  B.  at  50°  F.  He  uses  a  battery  of  four  pairs  of 
Smee's  or  three  Bunsen's  cells,  with  elements  arranged  for  in- 
tensity, and  electrolyzes  the  solutions  at  140°  F.  The  first  solu- 
tion will  decompose  without  an  aluminium  anode,  but  the  others 
require  such  an  anode  on  the  negative  pole.  The  solution  must 
be  acidulated  slightly  with  acid  corresponding  to  the  salt  used, 
the  temperature  being  kept  at  140°  F.  constantly. 

M.  A.  Bertrandf  states  that  he  deposited  aluminium  on  a  plate 
of  copper  from  a  solution  of  double  chloride  of  aluminium  and 
ammonia,  by  using  a  strong  current,  and  the  deposit  was  capable 
of  receiving  a  brilliant  polish. 

Jas.  S.  Haurd,J  of  Springfield,  Mass.,  patented  the  electrolysis 
of  an  aqueous  solution  formed  by  dissolving  cryolite  in  a  solution 
of  magnesium  and  mauganous  chlorides. 

John  Braun§  decomposes  a  solution  of  alum,  of  specific  gravity 
1.03  to  1.07,  at  the  usual  temperature,  using  an  insoluble  anode. 
In  the  course  of  the  operation,  the  sulphuric  acid  set  free  is  neu- 
tralized by  the  continual  addition  of  alkali ;  and-,  afterwards,  to 
avoid  the  precipitation  of  alumina,  a  non-volatile  organic  acid, 
such  as  tartaric,  is  added  to  the  solution.  The  intensity  of  the 
current  is  to  be  so  regulated  that  for  a  bath  of  10  to  20  litres  two 
Bunsen  elements  (about  20  centimetres  high)  are  used. 

Dr.  Fred.  Fischer ||  stated  that  Braun's  proposition  was  con- 
trary to  his  experience.  By  passing  a  current  of  8  to  9  volts  and 

*  Annual  Record  of  Science  and  Industry,  1875. 

f  Chem.  News,  xxxiv.  227. 

t  U.  S.  Patent,  228,900,  June  15,  1880. 

§  German  Patent,  No.  28,760  (1883). 

II  Zeitschrift  des  Vereins  Deutsche  Ingenieurs,  1884,  p.  557. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  253 

50  amperes,  using  from  0.1  to  10  amperes  per  sq.  centimetre  of 
cathode,  with  various  neutral  and  basic  aluminium  sulphate  solu- 
tions, with  and  without  organic  acids,  he  obtained  no  aluminium. 
He  obtained  a  black  deposit  of  copper  sulphide  on  the  copper 
anode,  which  had  apparently  been  mistaken  by  Braun  for  alu- 
minium. 

Moses  G.  Farmer*  has  patented  an  apparatus  for  obtaining 
aluminium  electrically  consisting  of  a  series  of  conducting  cells 
in  the  form  of  ladles,  each  ladle  having  a  handle  of  conducting 
material  extending  upwards  above  the  bowl  of  the  next  succeed- 
ing ladle ;  each  ladle  can  be  heated  separately  from  the  rest ;  the 
anodes  are  hung  in  the  ladles,  being  suspended  from  the  handles 
of  the  preceding  ladles,  the  ladles  themselves  being  the  cathodes. 

M.  L.  Senetf  electrolyzes  a  saturated  solution  of  aluminium 
sulphate,  separated  by  a  porous  septum  from  a  solution  of  sodium 
chloride.  A  current  is  used  of  6  to  7  volts  and  4  amperes.  The 
double  chloride,  APCl6.2NaCl,  is  formed,  then  decomposed,  and 
the  aluminium  liberated  deposited  on  the  negative  electrode. 
It  has  later  been  remarked  of  this  process  that  it  has  not  had  the 
wished-for  success  on  a  large  scale. 

Col.  Frismuth,  Philadelphia,  purports  to  plate  an  alloy  of 
nickel  -and  aluminium.  He  uses  an  ammoniacal  solution,  prob- 
ably of  their  sulphates.  The  plating  certainly  resembles  nickel, 
but  whether  it  contains  aluminium  the  author  has  not  been  able 
to  determine. 

Baron  Overbeck  and  H.  Xeiwerth,  of  Hannover,  J  have  patented 
the  following  process :  An  aqueous  or  other  solution  of  an  or- 
ganic salt  of  aluminium  is  used,  or  a  mixture  of  solutions  which 
by  double  decomposition  will  yield  such  salt.  Or  a  mixture  of  a 
metallic  chloride  and  aluminium  sulphate  may  be  used,  this 
yielding  nascent  aluminium  chloride,  which  the  current  splits  up 
immediately  into  aluminium  and  chlorine. 

Herman  Rienbold§  gives  the  following  recipe,  stating  that  it 
furnishes  excellent  results  :  50  parts  of  potash  alum  are  dissolved 

*  U.  S.  Patent,  No.  315,266,  April,  1885. 
f  Cosmos  les  Mondes,  Aug.  10,  1885. 
J  English  Pat.,  Dec.  15,  1883,  No.  5756. 
§  Jeweller's  Journal,  September,  1887. 


254  ALUMINIUM. 

in  300  parts  of  water,  and  to  this  are  added  10  parts  of  aluminium 
chloride.  The  whole  is  then  heated  to  200°  F.,  cooled,  and  then 
39  parts  of  potassium  cyanide  added.  A  weak  current  should  be 
used.  It  is  stated  that  the  plating,  when  polished,  will  be  found 
equal  to  the  best  silver  plating.  "  Iron/7  noticing  this  process, 
remarks,  "there  are  a  number  of  formula?  for  electro-plating  with 
aluminium,  but  few  appear  to  have  attained  to  practical  utility  in 
the  arts,  for  the  reason  that  there  is  no  special  demand  for  such 
processes.  All  the  qualities  that  are  possessed  by  an  electro-de- 
posit of  aluminium  are  possessed  to  an  equal  or  superior  degree 
by  other  metals,  silver,  nickel,  platinum,  etc.  Furthermore,  it 
obstinately  refuses  to  take  and  to  retain  a  high  lustre."  This 
criticism  is  a  little  overdrawn,  since  the  one  quality  in  which  alu- 
minium is  superior  to  silver — not  blackening  by  contact  with 
sulphurous  vapor — is  not  mentioned. 

Under  the  name  of  Count  R.  de  Montegelas,  of  Philadelphia, 
several  patents  have  been  taken  out  in  England  for  the  electrol- 
ysis of  aqueous  solutions,  which  may  be  summarized  as  follows  : — 

*  Alumina  is  treated  with  hydrochloric  acid,  and  aluminium 
chloride  obtained  in  solution.  The  liquid  is  then  placed  in  a 
vessel  into  which  dip  a  suitable  anode  and  a  cathode  of  brass  or 
copper.  On  passing  an  electric  current  through  the  bath  the  iron 
present  in  the  liquid  is  first  deposited,  and  as  soon  as  this  deposi- 
tion ceases  (as  is  apparent  by  the  change  of  color  of  the  deposit) 
the  liquid  is  decanted  into  another  similar  bath,  and  to  it  is  added 
about  fifty  per  cent,  by  weight  of  the  oxide  of  either  lead,  tin  or 
zinc.  On  sending  a  current  through  this  bath,  aluminium  to- 
gether with  the  metal  of  the  added  oxide  is  said  to  be  deposited 
on  the  cathode. 

fA  rectangular  vessel  is  divided  into  two  unequal  compartments 
by  a  vertical  porous  partition,  into  the  smaller  of  which  is  placed 
a  saturated  solution  of  common  salt,  in  which  is  immersed  a  brass 
or  copper  electrode,  into  the  larger  is  put  a  solution  of  aluminium 
chloride,  immersed  in  which  is  an  aluminium  electrode.  On  pass- 
ing the  current  the  latter  solution,  which  is  normally  yellow,  is 

*  English  Patent,  Aug.  18,  1886,  No.  10607. 
f  English  Patent,  Feb.  3,  1887,  No.  1751. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  255 

gradually  decolorized  and  converted  into  a  solution  of  aluminium- 
sodium  chloride.  When  colorless,  this  solution  is  taken  out  and 
the  aluminium  deposited  in  a  similarly  arranged  vessel.  The 
double  chloride  solution  is  placed  in  the  larger  compartment,  with 
an  electrode  of  brass,  copper,  or  a  thin  plate  of  aluminium,  while 
the  smaller  compartment  contains  a  carbon  electrode  dipping  into 
a  solution  of  salt  and  surrounded  by  fragments  of  a  mixture  of 
salt  and  double  chloride,  fused  together  in  equal  parts. 

The  author  has  been  given  several  ounces  of  a  very  fine,  metal- 
lic powder  said  to  have  been  made  by  these  processes,  and  which 
is  certainly  aluminium.  As  I  am  not  satisfied,  however,  that  the 
specimen  is  really  authentic,  I  feel  justified  in  suspending  a  final 
expression  of  opinion  on  the  process. 

A.  Walker,  of  Tarnowitz,  has  patented  the  following  methods 
of  procedure  : — * 

a.  Pure  commercial  hydrate  is  dissolved  in   nitric  acid  free 
from  chlorine,  in  slight  excess,  and  tartaric  acid  added.     The 
liquid  is  let  clear  for  some  time,  any  potassium  bi-tartrate,  which 
may  be  formed  from  small  quantities  of  potassium  adhering  to 
the   hydrate,   filtered   out,  and  the   clear   solution  electrolyzed. 
There  is  added  to  the  solution  during  electrolysis  organic  acid — 
as  formic,  acetic,  citric,  oxalic — or,  better,  absolute  alcohol. 

b.  A  solution  of  aluminium  nitrate,  as  far  as  possible  free  from 
alkalies  and  sulphuric  acid,  is  decomposed  by  a  strong  dynamic 
current  in  baths  arranged  in  series,  using  platinized  plates  as 
anode   and    cathode.     With    a  weak   current   of  0.02    to   0.05 
amperes  to  a  square  centimetre,  the  aluminium   separates  out  on 
the  cathode  as  a  deep  black  deposit,  sticking  close  to  the  copper. 
The  cathode  is  lifted  from  the  solution,  freed   from  small  quanti- 
ties of  alumina  coating  it  by  gentle  rinsing,  and  then  the  deposit 
washed  off  by  a  strong  jet  of  water.     The  powder  obtained  is 
washed  further  with  clear,  cold  water  particularly  free  from  so- 
dium chloride,  and  dried  by  gentle  heating  in  the  air. 

H.  C.  Bullf  proposes  to  manufacture  aluminium  alloys  by 
using  the  metal  to  be  alloyed  with  aluminium  as  a  cathode  in  a 

*  German  Pat.  (D.  R.  P.)  40,626  (1887.) 
f  English  Pat.,  10199  A.  (1887). 


256  .        ALUMINIUM. 

bath  of  aluminium  sulphate,  the  anode  being  either  of  aluminium 
or  of  an  insoluble  substance.  When  enough  aluminium  is  de- 
posited, the  cathode  is  taken  out  and  melted  down. 

C.  A.  Burghardt  and  W.  J.  Twining,  of  Manchester,  England, 
have  patented  the  following  methods  : — 

*To  a  solution  of  sodium  or  potassium  aluminate  containing 
about  7.2  oz.  of  aluminium  per  gallon  are  added  4  pounds  of  95 
percent,  potassium  cyanide  dissolved  in  a  quart  of  water,  and 
then  gradually  2J  pounds  of  potassium  bi-carbonate.  The 
whole  is  boiled  12  hours  and  made  up  to  a  gallon.  The  bath  is 
used  at  175°  F.  with  aluminium  or  platinum  anode  and  a  carbon 
or  copper  cathode.  The  addition  of  a  little  free  hydrocyanic 
acid  insures  a  bright  deposit  when  articles  are  being  plated. 

fTwo  and  one-half  kilos  of  aluminium  sulphate  in  solution  is 
precipitated  by  ammonia,  and  then  re-dissolved  by  adding  1 J  kilos 
of  caustic  soda  dissolved  in  a  litre  of  water ;  the  alumina  is  thus 
slightly  in  excess.  Then  hydrocyanic  acid  is  added  until  a  slight 
precipitate  appears.  This  solution,  warmed  to  80°,  is  used  as  a 
bath  from  which  aluminium  is  to  be  deposited. 

{The  bath  is  prepared  by  dissolving  alumina  in  a  solution  of 
chloride  of  copper,  and  treating  further  with  caustic  soda  or 
potash  for  the  purpose  of  causing  the  aluminium  and  copper  to 
combine  together.  The  precipitate,  dissolved  in  hydrocyanic 
acid  and  diluted,  forms  a  bath  of  double  cyanide,  which  when 
electrolyzed  deposits  an  alloy  of  aluminium  and  copper. 

Besides  the  processes  so  far  described,  patents  have  been  taken 
out  in  England  by  Gerhard  and  Smith,§  Taylor,||  and  Coulson,Tf 
the  details  of  which  have  not  been  accessible  to  the  author. 

Over  against  all  these  statements  and  claims  of  enthusiastic 
inventors,  let  me  place  a  few  cool  statements  from  authorities  who 
have  given  much  time  and  attention  to  elucidating  the  subject. 

Sprague**  states  his  inability  to  deposit  aluminium  electrically 
from  solution. 

*  English  Pat.,  July  2,  1887,  No.  9389. 

f  German  Pat.  (D.  R.  P.),  45,020  (1887). 

J  English  Pat.,  Oct.  28,  1887,  No.  2602. 

§  No.  16,653(1884).  ||  No.  1991  (1855). 

1  No.  2075  (1857).  **  Sprague's  Electricity,  p.  309. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  257 

Dr.  Clemens  Winekler*  states  that  he  has  spent  much  time  in 
trying  all  methods  so  far  proposed,  and  comes  to  the  conclusion 
that  aluminium  cannot  be  deposited  by  electricity  in  the  wet  way. 

Dr.  Geo.  Goref  although  having  once  proposed  a  method  which 
he  said  attained  this  end,  yet  in  his  later  work  on  Electro-metal- 
lurgy does  not  mention  his  former  proposition,  and  quotes  ap- 
parently as  coinciding  with  his  own  opinion,  the  words  of  Sprague 
and  Winekler  given  above. 

Dr.  S.  MierzinskiJ  states,  in  1883,  that  "the  deposition  of 
aluminium  from  an  aqueous  solution  of  its  salt  has  not  yet  been 
accomplished." 

Dr.  "W.  Hampe§  claims  to  have  shown  that  the  electrolysis  of 
aqueous  aluminous  solutions,  although  frequently  patented,  is  not 
to  be  expected.  From  which  we  would  infer  that  he  could  not 
testify  to  it  ever  having  been  done. 

Alexander  Watt||  holds  that  the  electrolytic  production  of 
aluminium  from  solution  is  very  improbable.  He  tried  acid 
solutions,  alkaline  solutions,  cyanide  combinations,  etc.,  under 
most  varied  conditions,  without  any  result. 

Finally,  I  will  quote  from  a  letter  of  my  good  friend  Dr. 
Justin  D.  Lisle,  of  Springfield,  O.,  who  with  ample  means  at 
his  disposal,  an  enthusiasm  bred  of  love  for  scientific  truth  and 
talent  to  guide  him  in  his  work,  has  reached  the  following  results  : 
"  I  have  tried  in  almost  every  conceivable  way  to  deposit  it  (alu- 
minium) from  aqueous  solution  by  electricity,  using  from  1  pint 
cells  to  60  gallon  cells  successively ;  the  cells  were  connected  for 
quantity  and  for  intensity  ;  acid  and  neutral  solutions  were  used  ; 
carbon,  platinum,  and  copper  electrodes ;  porous  cups  and  dia- 
phragms, were  all  thoroughly  tried  without  the  slightest  deposit 
of  metal.  In  some  cases  alumina  was  deposited,  which  has 
led  me  to  think  that  aluminium  was  primarily  deposited,  and 
owing  to  the  fine  state  in  which  it  existed  was  promptly  oxidized." 

*  Journal  of  the  Chem.  Soc.,  X.  1134. 
f  Text  book  of  Electro-metallurgy, 
t  Die  Fabrikation  des  Aluminiums. 
§  Chem.  Zeit.  (Cothen),  XL  935. 
H  London  Electrical  Review,  July,  1887. 
17 


258  ALUMINIUM. 

II. 

THE  ELECTKIC  DECOMPOSITION  OF  FUSED  ALUMINIUM 
COMPOUNDS. 

This  subdivision  of  the  electrolytic  methods  includes  all  the 
electric  processes  which  have  given  practical  results.  Under  this 
head  come  Davy's  first  attempts  to  decompose  alumina,  in  1807, 
Deville's  first  success  in  producing  pure  aluminium,  in  1854,  and 
GratzePs  application  of  the  dynamo-electric  machine,  in  1883, 
which  introduced  the  first  radical  improvement  the  aluminiun  in- 
dustry had  known  for  twenty-five  years.  It  is  hardly  too  much 
to  say  that  if  the  long  sought  for  method  of  turning  the  potential 
energy  of  coal  directly  into  electric  energy  ever  be  accomplished, 
these  electrolytic  methods  will  be  beyond  doubt  the  future  means 
of  bringing  aluminium  in  price  among  the  common  metals. 

There  seem  to  be  two  ways  of  operating,  as  mentioned  on  p. 
34,  in  the  first  of  which  the  liquid  compound  is  decomposed  at 
moderate  temperatures,  such  that  the  containing  vessel  can  be 
heated  to,  in  an  ordinary  fire,  and  in  which  almost  all  the  current 
is  utilized  in  decomposing  the  electrolyte  f  in  the  other  enormous 
temperatures  are  reached  by  means  of  interrupting  a  powerful 
current,  and  a  large  part  of  the  electric  energy  is  converted  into 
heat,  while  the  decomposition  may  be  partly  electrolytic  and 
partly  a  chemical  reaction  made  possible  by  this  extreme  tempera- 
ture. As  it  is  impossible  in  one  or  two  cases  to  draw  this  line, 
and  since  the  practical  requirements  of  the  two  methods  of  pro- 
cedure are  in  most  respects  identical,  we  will  consider  the  fol- 
lowing processes  in  their  chronological  order,  except  in  one  or 
two  cases  where  very  similar  ones  are  placed  together. 

Davy's  Experiment  (1810). 

Sir  Humphry  Davy,  in  his  Brompton  Lecture  before  the 
Royal  Philosophical  Society,*  described  the  following  attempt 
to  decompose  alumina  and  obtain  the  metal  of  this  earth.  He 

*  Philosophical  Transactions,  1810. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  259 

connected  an  iron  wire  with  the  negative  pole  of  a  battery  con- 
sisting of  1000  double  plates.  The  wire  was  heated  to  whiteness 
and  then  fused  in  contact  with  some  moistened  alumina,  the  opera- 
tion being  performed  in  an  atmosphere  of  hydrogen.  The  iron 
became  brittle,  whiter,  and  on  being  dissolved  in  acid  gave  a 
solution  from  which  was  precipitated  alumina,  identical  with 
that  used. 

Duvivier's  Experiment  (1854). 

M.  Duvivier*  states  that  by  passing  an  electric  current  from 
eighty  Bunsen  cells  through  a  small  piece  of  laminated  disthene 
between  two  carbon  points,  the  disthene  melted  entirely  in  two 
or  three  minutes,  the  elements  which  composed  it  were*  partly 
disunited  by  the  power  of  the  electric  current,  and  some  alumin- 
ium freed  from  its  oxygen.  Several  globules  of  the  metal 
separated,  one  of  which  was  as  white  and  as  hard  as  silver. 

Bunsen' s  and  Devitte's  Methods  (1854). 

A  method  of  decomposing  aluminium-sodium  chloride  by  the 
battery  was  discovered  simultaneously  by  Deville  in  France  and 
Bunsen  in  Germany,  in  1854,  and  is  nothing  else  but  an  applica- 
tion of  the  process  already  announced  by  Bunsen  of  decomposing 
magnesium  chloride  by  the  battery.  Deville  gives  the  more 
minute  account,  and  we  therefore  quote  his  description  of  the 
process. 

f"  It  appears  to  me  impossible  to  obtain  aluminium  by  the 
battery  in  aqueous  solutions.  I  should  believe  this  to  be  an 
absolute  impossibility  if  the  brilliant  experiments  of  M.  Bunsen 
in  the  preparation  of  barium,  chromium  and  manganese  did  not 
shake  my  convictions.  Still  I  must  say  that  all  the  processes 
of  this  description  which  have  recently  been  published  for  the 
preparation  of  aluminium  have  failed  to  give  me  any  results. 
Every  one  knows  the  elegant  process  by  means  of  which  M. 
Bunsen  has  lately  produced  magnesium,  decomposing  fused  mag- 

*  The  Chemist,  Aug.  1854. 

f  Ann.  de  Chem.  et  de  Phys.  [3],  46,  452   ;  Deville's  de  1' Aluminium. 


260  ALUMINIUM. 

nesium  chloride  by  an  electric  current.  The  illustrious  professor 
at  Heidelberg  has  opened  up  a  method  which  may  lead  to  very 
interesting  results.  However,  the  battery  cannot  be  used  for  de- 
composing aluminium  chloride  directly,  which  does  not  melt,  but 
volatilizes  at  a  low  temperature  ;  it  is,  therefore,  necessary  to  use 
some  other  material  which  is  fusible  and  in  which  aluminium 
alone  will  be  displaced  by  the  current.  I  have  found  this  salt 
in  the  double  chloride  of  aluminium  and  sodium,  which  melts 
towards  185°,  is  fixed  at  a  somewhat  high  temperature,  although 
volatile  below  the  fusing  point  of  aluminium,  and  thus  unites  all 
the  desirable  conditions. 

"  I  put  some  of  this  double  chloride  into  a  porcelain  crucible 
separated  imperfectly  into  two  compartments  by  a  thin  leaf  of 
porcelain,  and  decomposed  it  by  means  of  a  battery  of  five  ele- 
ments and  carbon  electrodes.  The  crucible  was  heated  more  and 
more  as  the  operation  progressed,  for  the  contents  became  less  and 
less  fusible,  but  the  heat  was  not  carried  past  the  melting  point  of 
aluminium.  Arrived  at  this  point,  after  having  lifted  out  the 
diaphragm  and  electrodes,  I  heated  the  crucible  to  bright  redness 
and  found  at  the  bottom  a  button  of  aluminium,  which  was 
flattened  out  and  shown  to  the  Academy  in  the  Seance  of  March 
20,  1854.  The  button  was  accompanied  by  a  considerable  quan- 
tity of  carbon,  which  prevented  the  union  of  a  considerable  mass 
of  shot-metal.  This  carbon  came  from  the  disintegration  of  the 
very  dense  gas-retort  carbon  electrodes  ;  in  fact,  the  positive  elec- 
trode was  entirely  eaten  away  in  spite  of  its  considerable  thick- 
ness. It  was  evident,  then,  that  this  apparatus,  although  similar 
to  that  adopted  by  Bunsen  for  manufacturing  magnesium,  would 
not  suit  here,  and  the  following  is  the  process  which  after  many 
experiments  I  hold  as  best. 

"  To  prepare  the  bath  for  decomposition,  I  heat  a  mixture  of  2 
parts  aluminium  chloride  and  1  part  sodium  chloride,  dry  and 
pulverized,  to  about  200°  in  a  porcelain  capsule.  They  combine 
with  disengagement  of  heat,  and  the  resulting  bath  is  very  fluid. 
The  apparatus  which  I  use  for  the  decomposition  comprises  a 
glazed  porcelain  crucible,  which  as  a  precaution  is  placed  inside 
a  larger  one  of  clay.  The  whole  is  covered  by  a  porcelain 
cover  pierced  by  a  slit  to  give  passage  to  a  large  thick  leaf  of 


KEDUCTION   BY   THE    USE   OF   ELECTRICITY. 


261 


platinum,  which  serves  as  the  negative  electrode;  the  lid  has 
also  a  hole  through  which  is  introduced,  fitting  closely,  a  well- 
dried  porous  cylinder,  the  bottom  of  which  is  kept  at  some  dis- 
tance from  the  inside  of  the  porcelain  crucible.  This  porous 
vessel  encloses  a  pencil  of  retort  carbon,  which  serves  as  the 
positive  electrode.  Melted  double  chloride  is  poured  into  the 
porous  jar  and  into  the  crucible  so  as  to  stand  at  the  same  height 
in  both  vessels ;  the  whole  is  heated  just  enough  to  keep  the  bath 
in  fusion,  and  there  is  passed  through  it  the  current  from  several 
Bunsen  cells,  two  cells  being  strictly  sufficient.  The  annexed 
diagram  shows  the  crucibles  in  section. 

Fig.  23. 


"  The  aluminium  deposits  with  some  sodium  chloride  on  the 
platinum  leaf;  the  chlorine,  with  a  little  aluminium  chloride,  is 
disengaged  in  the  porous  jar  and  forms  white  fumes,  which  are 
prevented  from  rising  by  throwing  into  the  jar  from  time  to  time 
some  dry,  pulverized  sodium  chloride.  To  collect  the  aluminium, 
the  platinum  leaf  is  removed  when  sufficiently  charged  with  the 
saline  and  metallic  deposit ;  after  letting  it  cool,  the  deposit  is 
rubbed  off  and  the  leaf  placed  in  its  former  position.  The 


262  ALUMINIUM. 

material  thus  detached,  melted  in  a  porcelain  crucible,  and  after 
cooling  washed  with  water,  yields  a  gray,  metallic  powder,  which 
by  melting  several  times  under  a  layer  of  the  double  chloride  is 
reunited  into  a  button." 

Bunsen*  adopted  a  similar  arrangement.  The  porcelain  cru- 
cible containing  the  bath  of  aluminium-sodium  chloride  kept  in 
fusion  was  divided  into  two  compartments  in  its  upper  part  by  a 
partition,  in  order  to  separate  the  chlorine  liberated  from  the  alu- 
minium reduced.  He  made  the  two  electrodes  of  retort  carbon. 
To  reunite  the  pulverulent  aluminium,  Bunsen  melted  it  in  a  bath 
of  the  double  chloride,  continually  throwing  in  enough  sodium 
chloride  to  keep  the  temperature  of  the  bath  about  the  fusing 
point  of  silver. 

As  we  have  seen,  Deville,  without  being  acquainted  with  Bun- 
sen's  investigations,  employed  the  same  arrangement,  but  he 
abandoned  it  because  the  retort  carbon  slowly  disintegrated  in  the 
bath,  and  a  considerable  quantity  of  double  chloride  was  lost  by  the 
higher  heat  necessary  to  reunite  the  globules  of  aluminium  after 
the  electrolysis.  Deville  also  observed  that  by  working  at  a 
higher  temperature,  as  Bunsen  has  done,  he  obtained  purer  metal, 
but  in  less  quantity.  The  effect  of  the  high  heat  is  that  silicon 
chloride  is  formed  and  volatilizes,  and  the  iron  which  would  have 
been  reduced  with  the  aluminium  is  transformed  into  ferrous 
chloride  by  the  aluminium  chloride,  and  thus  the  aluminium  is 
purified  of  silicon  and  iron. 

Plating  aluminium  on  copper. — The  same  bath  of  double  chlor- 
ide of  aluminium  and  sodium  may  be  used  for  plating  alumin- 
ium in  particular  on  copper,  on  which  Capt.  Caron  experimented 
with  Deville.  Deville  says  :  "  To  succeed  well,  it  is  necessary  to 
use  a  bath  of  double  chloride  which  has  been  entirely  purified 
from  foreign  metallic  matter  by  the  action  of  the  battery  itself. 
When  aluminium  is  being  deposited  at  the  negative  pole,  the  first 
portions  of  metal  obtained  are  always  brittle,  the  impurities  in 
the  bath  being  removed  in  the  first  metal  thrown  down  ;  so,  when 
the  metal  deposited  appears  pure,  the  piece  of  copper  to  be  plated 
is  attached  to  this  pole  and  a  bar  of  pure  aluminium  to  the  posi- 

*  Pogg.  Annalen,  97,  648. 


KEDUCTION   BY   THE   USE   OF   ELECTRICITY.  263 

live  pole.  However,  a  compact  mixture  of  carbon  and  alumina 
can  be  used  instead  of  the  aluminium  anode,  which  acts  similarly 
to  it  and  keeps  the  composition  of  the  bath  constant.  The  tem- 
perature ought  to  be  kept  a  little  lower  than  the  fusing  point  of 
aluminium.  The  deposit  takes  place  readily  and  is  very  ad- 
herent, but  it  is  difficult  to  prevent  it  being  impregnated  with 
double  chloride,  which  attacks  it  the  moment  the  piece  is  washed. 
The  washing  ought  to  be  done  in  a  large  quantity  of  water. 
Cryolite  might  equally  as  well  be  used .  for  this  operation,  but  its 
fusibility  should  be  increased  by  mixing  with  it  a  little  double 
chloride  of  aluminium  and  sodium  and  some  potassium  chloride." 

Le  Chatellier's  Method  (1861). 

The  subject  of  this  patent*  was  the  decomposition  of  the  fused 
double  chloride  of  aluminium  and  sodium,  with  the  particular 
object  of  coating  or  plating  other  metals,  the  articles  being  at- 
tached to  the  negative  pole.  About  the  only  novelty  claimed  in 
this  patent  was  the  use  of  a  mixture  of  alumina  and  carbon  for  the 
anode,  but  we  see  from  the  previous  paragraph  that  this  was  sug- 
gested by  Deville  several  years  before ;  the  only  real  improve- 
ment was  the  placing  of  this  anode  inside  a  porous  cup,  in  order 
to  prevent  the  disintegrated  carbon  from  falling  into  the  bath. 

Monckton's  Patent  (1862). 

Moncktonf  proposes  to  pass  an  electric  current  through  a  re- 
duction chamber,  and  in  this  way  to  raise  the  temperature  to  such 
a  point  that  alumina  will  be  reduced  by  the  carbon  present.  We 
clearly  see  in  this  the  germ  of  several  more-recently  patented 
processes. 

Gaudirfs  Process  (1869). 

GaudinJ  reduces  aluminium  by  a  process  to  which  he  applies 
the  somewhat  doubtful  title  of  economic.  He  melts  together 

*  English  Patent,  1861,  No.  1214.  f  English  Patent,  1862,  No.  264. 

$  Moniteur  Scientifique,  xi.  62. 


264  ALUMINIUM. 

equal  parts  of  cryolite  and  sodium  chloride,  and  traverses  the 
fused  mass  by  a  galvanic  current.  Fluorine  is  evolved  at  the 
positive  pole,  while  aluminium  accumulates  at  the  negative. 

Kagensbuscti  s  Process  (1872). 

Kagensbusch,*  of  Leeds,  proposes  to  melt  clay  with  fluxes, 
then  adding  zinc  or  a  like  metal  to  pass  an  electric  current 
through  the  fused  mass,  isolating  an  alloy  of  aluminium  and  the 
metal,  from  which  the  foreign  metal  may  be  removed  by  distilla- 
tion, sublimation,  or  cupellation. 

Berthaufs  Proposition  (1879). 

Up  to  this  time,  all  the  proposed  electric  processes  were  con- 
fined to  the  use  of  a  galvanic  current,  the  cost  of  obtaining  which 
was  a  summary  bar  to  all  ideas  of  economical  production.  About 
this  period  dynamo-electric  machines  were  being  introduced  into 
metallurgical  practice,  and  Berthaut  is  the  first  we  can  find  who 
proposes  their  use  in  producing  aluminium.  The  process  which 
he  patentedf  is  otherwise  almost  identical  with  Le  Chatellier's. 

Grated? 8  Process  (1883). 

This  process^  has  little  claim  to  originality,  except  in  the  de- 
tails of  the  apparatus.  A  dynamo-electric  current  is  used,  the 
electrolyte  is  fused  cryolite  or  double  chloride  of  aluminium  and 
sodium,  and  the  anodes  are  of  pressed  carbon  and  alumina — none 
of  which  points  are  new.  However,  the  use  of  melting  pots  of 
porcelain,  alumina,  or  aluminium,  and  making  them  the  negative 
electrode  are  points  in  which  innovations  are  made. 

In  a  furnace  are  put  two  to  five  pots,  according  to  the  power 
of  the  dynamo  used,  each  pot  having  a  separate  grate.  The  pots 
are  preferably  of  metal,  cast-steel  is  used,  and  form  the  negative 
electrodes.  The  positive  electrode,  K  (Fig.  24),  can  be  made  of 

*  English  Patent,  1872,  No.  4811. 

f  English  Patent,  1879,  No.  4087. 

t  German  Patent  (D.  R.  P.);  No.  26962  (1883). 


REDUCTION   BY   THE   USE   OF   ELECTRICITY. 


265 


a  mixture  of  anhydrous  alumina  and  carbon  pressed  into  shape 
and  ignited.  A  mixture  of  alumina  and  gas-tar  answers  very 
well ;  or  it  can  even  be  made  of  gas-tar  and  gas-retort  carbon. 

Fig.  24. 


During  the  operation  little  pieces  of  carbon  fall  from  it  and 
would  contaminate  the  bath,  but  are  kept  from  doing  so  by  the 
mantle,  G.  This  isolating  vessel,  G9  is  perforated  around  the 
lower  part  at  g,  so  that  the  molten  electrolyte  may  circulate 
through.  The  tube  O1  conducts  reducing  gas  into  the  crucible, 
which  leaves  by  the  tube  O2.  This  reducing  atmosphere  is  im- 
portant, in  order  to  protect  from  burning  any  metal  rising  to  the 
surface  of  the  bath.  The  chlorine  set  free  at  the  electrode,  K, 
partly  combines  with  the  alumina  in  it,  regenerating  the  bath, 
but  some  escapes,  and,  collecting  in  the  upper  part  of  the  sur- 
rounding mantel,  Gr,  is  led  away  by  a  tube  connecting  with  it. 
Instead  of  making  the  electrode,  K,  of  carbon  and  alumina,  it 
may  simply  be  of  carbon,  and  then  plates  of  pressed  alumina  and 
carbon  are  placed  in  the  bath  close  to  the  electrode,  K,  but  not 
connected  with  it.  Also,  in  place  of  making  the  crucible  of  metal 


266  ALUMINIUM. 

and  connecting  it  with  the  negative  pole,  it  may  be  made  of  a 
non-conducting  material,  clay  or  the  like,  and  a  metallic  electrode 
— as,  for  instance,  of  aluminium — plunged  into  the  bath. 

In  a  later  patent,*  Gratzel  states  that  the  bath  is  decomposed 
by  a  current  of  comparatively  low  tension  if  magnesium  chloride 
be  present ;  the  chlorides  of  barium,  strontium,  or  calcium  act 
similarly. 

Prof.  F.  Fischerf  maintains  as  impracticable  the  use  of  plates 
of  pressed  alumina  and  carbon,  which  can,  further,  only  be  opera- 
tive when  they  are  made  the  positive  electrode,  and  then  their 
electric  resistance  is  too  great.  The  incorporation  into  them  of 
copper  filings,  saturation  with  mercury,  etc.,  gives  no  more  prac- 
tical results.  There  are  also  volatilized  at  the  anodes  considerable 
quantities  of  aluminium  chloride,  varying  in  amount  with  the 
strength  of  the  current. 

Large  works  were  erected  near  Bremen  by  the  Aluminium 
und  Magnesiumfabrik  Pt.  Gratzel,  zu  Hemelingen,  in  which 
this  process  was  installed.  License  was  also  granted  to  the  large 
chemical  works  of  Schering,  at  Berlin,  to  operate  it.  R.  Bieder- 
mann,  in  commenting  on  the  process  in  1886,J  stated  that  the 
results  obtained  so  far  were  not  fully  satisfactory,  but  the  diffi- 
culties which  had  been  met  were  of  a  kind  which  would  certainly 
be  overcome.  They  were  principally  in  the  polarization  of  the 
cathode,  by  which  a  large  part  of  the  current  was  neutralized. 
By  using  proper  depolarizing  substances  this  difficulty  would  be 
removed.  The  utilization  of  the  chlorine  evolved  would  also 
very  much  decrease  the  expenses.  A  more  suitable  slag,  which 
collected  the  aluminium  together  better,  was  also  desirable. 
Finally,  the  metal  produced  was  somewhat  impure,  taking  up 
iron  from  the  iron  pots  and  silicon  from  the  clay  ones,  to  obviate 
which  Biedermann  recommended  the  use  of  lime  or  magnesia 
vessels. 

Prof.  Fischer,  as  we  have  seen,  maintained  the  uselessness  of 
GratzePs  patent  claims,  and  his  later  expression  of  this  opinion 

*  English  Patent,  14325,  Nov.  23,  1885.  U.  S.  Patent,  362441,  May  3, 
1887. 

f  Wagner's  Jahresbericht,  1884,  p.  1319  ;  1887,  p.  376. 
J  Kerl  und  Stohinan,  4th  ed.,  p.  725. 


[REDUCTION   BY   THE   USE   OF    ELECTRICITY.  267 

in  1887  drew  a  reply  from  A.  Saarburger,*  director  of  the  works 
at  Hemelingen,  to  the  eifect  that  since  October,  1887,  they  had 
abandoned  the  Gratzel  process  and  were  making  aluminium  at 
present  by  methods  devised  by  Herr  Saarburger;  in  consequence 
of  which  fact  the  directors  of  the  company  decided  in  January, 
1888,  to  drop  the  addition  Pt.  Gratzel  from  the  firm  name.  The 
methods  now  in  use  at  Hemelingen  are  kept  secret,  but  the 
author  is  informed  by  a  friend  in  Hamburg  that  they  are  using 
a  modified  Deville  sodium  process.  Herr  Saarburger  informed 
me  in  October,  1888,  that  they  were  producing  pure  aluminium 
at  the  rate  of  12  tons  a  year,  besides  a  large  quantity  sold  in 
alloys.  An  attractive  pamphlet  issued  by  this  firm  sets  forth 
precautions  to  be  used  in  making  aluminium  alloys,  together 
with  a  digest  of  their  most  important  properties,  which  we  shall 
have  occasion  to  quote  from  later  in  considering  those  alloys. 

•Kleiner's  Process  (1886). 

This  was  devised  by  Dr.  Ed.  Kleiner  of  Zurich,  Switzerland,  and 
has  presumably  been  patented  in  most  of  the  European  States. 
The  English  patent  is  dated  1886.f  The  first  attempts  to  operate 
it  were  at  the  Rhine  Falls,  Schaffhausen,  and  were  promising 
enough  to  induce  Messrs.  J.  G.  Nethers,  Sons  &  Co.,  proprietors 
of  an  iron  works  there,  to  try  to  obtain  water  rights  for  1500 
horse  power,  announcing  that  a  company  (the  Kleiner  Gesell- 
schaft)  with  a  capital  of  12,000,000  francs  was  prepared  to  under- 
take the  enterprise  and  build  large  works.  The  proposition  is 
said  to  have  met  with  strong  opposition  from  the  hotel-keepers 
and  those  interested  in  the  Falls  as  an  attraction  for  tourists,  and 
the  government  declined  the  grant,  considering  that  the  pictu- 
resqueness  of  the  falls  would  be  seriously  affected.  This  is  the 
reason  given  by  those  interested  in  the  process  for  it  not  being 
carried  out  in  Switzerland,  it  being  then  determined  to  start  a 
works  in  some  part  of  England  where  cheap  coal  could  be  ob- 
tained, and  test  the  process  on  a  large  scale.  A  small  experi- 

*  Verein  der  Deutsche  Ingenieure,  Jan.  26,  1889. 

f  English  Patents,  8531,  June  29,  1886,  and  15322,  Nov.  24,  1886. 


268  ALUMINIUM. 

mental  plant  was  then  set  up  in  the  early  part  of  1887  on  Far- 
rington  Road,  London,  where  it  was  inspected  by  many  scientific 
men,  among  them  Dr.  John  Hopkinson,  F.R.S.,  who  reported 
on  the  quantitative  results  obtained ;  a  description  of  the  process 
as  here  operated  was  also  written  up  for  "  Engineering."  With 
the  co-operation  of  Major  Ricarde-Seaver  a  larger  plant  was  put 
up  at  Hope  Mills,  Tydesley,  in  Lancashire,  where  the  process 
was  inspected  and  reported  on  by  Dr.  George  Gore,  the  electrician. 
After  his  report  we  learn  that  the  patents  have  been  acquired 
by  the  Aluminium  Syndicate,  Limited,  of  London,  a  combination 
of  capitalists  among  whom  are  said  to  be  the  Rothschilds.  The 
latest  reports  state  that  the  process  is  still  in  the  experimental 
stage,  although  Dr.  Kleiner  considers  that  the  present  results 
will  justify  working  on  a  commercial  scale  in  the  near  future. 

The  aluminium  compound  used  is  commercial  cryolite.  It  is 
stated  that  the  native  mineral  from  Greenland  contains  on  an 
average,  according  to  Dr.  Kleiner's  analysis,  96  per  cent,  of  pure 
cryolite,  the  remainder  being  moisture,  silica,  oxides  of  iron  and 
manganese.  As  pure  cryolite  contains  13  per  cent,  of  aluminium, 
the  native  mineral  will  contain  12J  per  cent.,  all  of  which  Dr. 
Kleiner  claims  to  be  able  to  extract.  It  is  further  remarked  that 
as  soon  as  sufficient  demand  arises,  an  artificial  cryolite  can  be 
made  at  much  less  cost  than  that  of  the  native  mineral,  which  now 
sells  at  £18  to  £20  a  ton.  The  rationale  of  the  process  consists 
in  applying  the  electric  current  in  such  a  way  that  a  small  quan- 
tity of  it  generates  heat  and  keeps  the  electrolyte  in  fusion,  while 
the  larger  quantity  acts  electrolytically.  Dry,  powdered  cryolite 
is  packed  around  and  between  carbon  electrodes  in  a  bauxite- 
lined  cavity  ;  on  passing  a  current  of  high  tension  (80  to  100  volts) 
through  the  electrodes,  the  cryolite  is  quickly  fused  by  the  heat  of 
the  arc  and  becomes  a  conductor.  As  soon  as  the  electrolyte  is 
in  good  fusion  the  tension  is  lowered  to  50  volts,  the  quantity 
being  about  150  amperes,  the  arc  ceases  and  the  decomposition 
proceeds  regularly  for  two  or  three  hours  until  the  bath  is  nearly 
exhausted.  The  evolved  fluorine  is  said  to  attack  the  beauxite 
and  by  thus  supplying  aluminium  to  the  bath  extends  the  time  of 
an  operation.  In  the  first  patent  the  negative  carbon  was  inserted 
through  the  bottom  of  the  melting  cavity,  the  positive  dipping 


REDUCTION    BY   THE   USE   OF   ELECTRICITY.  269 

into  the  bath  from  above,  but  it  was  found  that  while  the  ends 
of  the  positive  carbon  immersed  in  the  cryolite  were  unattacked, 
the  part  immediately  over  the  bath  was  rapidly  corroded.  In 
the  second  patent,  therefore,  the  positive  electrode  was  circular 
and  entirely  immersed  in  the  cryolite,  connection  being  made  by 
ears  which  projected  through  the  side  of  the  vessel.  As  the  car- 
bons are  thus  fixed,  .the  preliminary  fusion  is  accomplished  by  a 
movable  carbon  rod  suspended  from  above,  passing  through  the 
circular  anode  and  used  only  for  this  purpose.  The  bath  being 
well  fused  and  the  current  flowing  freely  between  the  fixed  car- 
bons, the  rod  is  withdrawn.  The  carbons  are  said  to  be  thus 
perfectly  protected  from  corrosion,  and  able  to  serve  almost  in- 
definitely. The  melting  pots  finally  used  were  ordinary  black- 
lead  crucibles,  which  are  not  usually  injured  at  all,  since  the  fused 
part  of  the  cryolite  does  not  touch  them,  and  they  last  as  many 
as  300  fusions.  After  the  operation,  the  carbons  are  lifted  out  of 
the  bath  and  the  contents  cooled.  When  solid,  the  crucibles  are 
inverted  and  the  contents  fall  out.  This  residue  is  broken  to 
coarse  powder,  the  nodules  of  aluminium  picked  out,  melted  in  a 
crucible  and  cast  into  bars.  The  coarse  powder  is  then  ground 
to  fine  dust.  This  powder  is  more  or  less  alkaline  and  contains 
a  greater  or  less  excess  of  fluoride  of  sodium  in  proportion  to  the 
amount  of  aluminium  which  has  been  taken  out.  If  only  a  small 
proportion  of  the  metal  has  been  extracted  and  the  powder  con- 
tains only  a  small  excess  of  sodium  fluoride,  it  is  used  again  with- 
out any  preparation  in  charging  the  crucibles ;  but  if  as  much  as 
5  or  6  per  cent,  of  aluminium  has  been  removed  and  the  powder, 
therefore,  contains  a  large  excess  of  sodium  fluoride,  it  is  washed 
with  water  for  a  long  time  to  remove  that  salt,  which  slowly  dis- 
solves. The  solution  is  reserved,  while  the  powder  remaining  is 
unchanged  cryolite,  and  is  used  over.  Dr.  Gore  states  that  if  the 
powder,  electrodes  and  crucible  are  perfectly  dry,  there  is  no 
escape  of  gas  or  vapor  during  the  process  ;  but  if  moisture  is  pre- 
sent, a  small  amount  only  of  fumes  of  hydrofluoric  acid  appear, 
and  that  there  is  no  escape  of  fluorine  gas  at  any  time.  If  this  is  so, 
it  is  rather  difficult  to  see  where  the  fluorine  with  which  the  alu- 
minium is  combined  goes  to.  If  the  vessel  were  lined  with 
beauxite,  it  might  be  retained  by  this  lining,  but  in  the  experi- 


270  ALUMINIUM. 

ments  seen  by  Dr.  Gore,  a  plumbago  crucible  was  used  (which  re- 
mained unattacked)  and  cryolite  only.  It  is  certainly  a  mystery 
how  any  aluminium  could  be  produced  without  fluorine  vapors 
being  liberated.  Dr.  Kleiner  hopes  to  soon  dispense  with  the 
interruption  of  the  process,  washing,  etc.,  by  regenerating  cryolite 
in  the  crucible  itself  and  so  making  the  process  continuous.  One 
of  the  great  advantages  claimed  is  that  the  aluminium  is  obtained 
in  nodules,  and  not  in  fine  powder ;  if  it  was,  it  could  not  all  be 
collected  because  it  is  so  light,  some  of  it  would  float  upon  the  water 
during  the  washing  process  and  be  lost,  and  even  when  collected 
it  could  not  be  dried  and  melted  without  considerable  loss. 

It  has  been  found  impossible  in  practice  to  obtain  all  the  alu- 
minium from  a  given  quantity  of  cryolite  in  less  than  two  fusions, 
for  the  sodium  fluoride  collecting  in  the  bath  hinders  the  produc- 
tion of  the  metal.  The  proportion  extracted  by  a  single  fusion  de- 
pends upon  its  duration.  In  the  operations  at  Tydesley,  a  fusion 
lasting  24  hours  separated  only  2J  per  cent,  of  aluminium, 
whereas  the  cryolite  contained  12  J  per  cent.  At  this  rate,  to  ex- 
tract the  whole  in  two  operations  would  require  two  fusions  of 
60  hours  each.  As  to  the  output,  on  an  average  a  current  of  38 
electric  horse  power  deposited  150  grammes  of  aluminium  per 
hour,  being  a  little  over  3  grammes  per  horse-power.  Since  a 
current  of  50  volts  and  150  amperes,  such  as  was  stated  above  as 

50  x  1 50 
the  current  in  each  pot,  is  equal  to or  10  electric  H.  P., 

it  is  probable  that  the  38  H.  P.  current  mentioned  must  have 
been  used  for  four  crucibles.  Now,  the  output  of  four  crucibles, 
each  with  a  current  of  150  amperes,  should  have  been  0.00009135 
X  150  x  4  s=  0.0548  grammes  per  second  or  197.3  grammes  per 
hour ;  the  difference  between  this  and  the  amount  actually  ob- 
tained, or  47.3  grammes,  is  the  amount  of  aluminium  which  was 
produced  and  then  afterwards  lost  either  as  fine  shot-metal  or 
powder  or  dissolved  again  by  corroding  elements  in  the  bath. 
To  calculate  how  the  output  of  3  grammes  per  electric  H.  P.  per 
hour  compares  with  the  quantity  of  metal  which  this  amount  of 
energy  should  be  able  to  produce,  we  need  to  know  the  heat  of 
formation  of  cryolite,  or  we  could  form  some  idea  if  we  knew 
even  that  of  aluminium  fluoride,  but  thermal  data  with  regard  to 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  271 

fluorides  are  entirely  lacking,  since  free  fluorine  is  needed  as  the 
basis  of  their  experimental  determination.  As  fluorine  has 
lately  been  isolated,  it  may  not  be  long  before  some  of  these 
figures  are  determined,  and  then  the  calculations  referred  to  can 
be  made.  In  the  mean  time  we  can  observe  no  further  than  that 
about  75  per  cent,  of  the  metal  produced  in  the  bath  is  obtained 
and  weighed,  and  that  the  high  potential  of  the  current  seems  to 
indicate  a  considerable  loss  of  power  in  overcoming  resistances 
other  than  that  of  decomposition,  a  loss  greater  than  is  met  with 
in.  other  somewhat  similar  operations. 

As  to  the  purity  of  the  metal  obtained,  the  process  is  met  at 
the  outset  by  the  silica  and  iron  oxide  in  the  cryolite,  which  are 
probably  all  reduced  with  the  first  few  grammes  of  aluminium 
thrown  down.  This  can  possibly  be  remedied  by  using  a  purer 
artificial  cryolite  ;  the  impurities  cannot  generally  be  separated 
from  the  natural  mineral.  Then  there  are  impurities  of  a  similar 
nature  coming  from  the  carbons  used,  and  which  are  generally 
present  if  especial  pains  are  not  taken  to  get  very  pure  materials 
for  making  them.  Dr.  Kleiner's  early  attempts  produced  metal 
of  85  to  95  per  cent,  purity,  but  he  now  states  that  it  is  uniformly 
95  to  98  per  cent.,  and  being  put  on  the  market  in  competition 
with  other  commercial  brands.  It  appears,  however,  from  a  con- 
sideration of  the  preceding  data,  that  unless  great  improvements 
have  since  been  made  in  several  details,  the  process  will  not 
enable  the  metal  produced  to  be  sold  at  16  shillings  a  pound  (the 
present  selling  price),  and  pay  expenses. 

Lossier's  Method. 

*This  is  a  device  for  decomposing  the  natural  silicates  by 
electricity  and  obtaining  their  aluminium.  The  bath  is  com- 
posed of  pure  aluminium  fluoride  or  of  a  mixture  of  this  salt 
and  an  alkaline  chloride,  and  is  kept  molten  in  a  round  bottomed 
crucible  placed  in  a  furnace.  The  electrodes  are  of  dense  carbon 
and  are  separated  in  the  crucible  by  a  partition  reaching  beneath 
the  surface  of  the  bath.  The  positive  electrode  is  furnished  with 

*  German  Patent  (D.  R.  P.),  No.  31089. 


272  ALUMINIUM. 

a  jacket  or  thick  coating  of  some  aluminium  silicate,  plastered 
on  moist  and  well  dried  before  use.  When  the  current  is  passed, 
the  aluminium  fluoride  yields  up  its  fluorine  at  this  pole  and  its 
aluminium  at  the  other.  The  fluorine  combines  with  the  alumin- 
ium silicate,  forming  on  the  one  hand  aluminium  fluoride,  which 
regenerates  the  bath,  on  the  other  silicon  fluoride  and  carbonic 
oxide,  which  escape  as  gases.  The  metal  liberated  at  the  negative 
pole  is  lighter  than  the  fused  bath,  and  therefore  rises  to  the 
surface. 

M.  Grabau  cites  as  one  of  the  recommendations  of  aluminium 
fluoride  for  use  in  his  process  (p.  242),  that  it  is  quite  infusible,  so 
it  would  appear  that  Lossier  has  made  a  mistake  in  supposing 
that  it  could  be  melted  alone  in  a  crucible.  It  would,  however, 
make  a  very  fusible  bath  when  the  alkali  chloride  was  added. 
It  is  probable  that  the  carrying  out  of  this  method  would  develop 
great  trouble  from  the  attacking  of  the  crucible  by  the  very 
corrosive  bath,  the  disintegration  of  the  carbons,  which  would 
cause  much  trouble  at  the  negative  pole  especially,  and  the  oxida- 
tion of  the  fluid  aluminium  on  the  surface  of  the  bath.  I  cannot 
learn  that  the  process  has  ever  been  attempted  on  a  large  scale. 

Omholfs  Furnace. 

I.  Omholt  and  the  firm  Bottiger  and  Seidler,  of  Gossnitz,  have 
patented  the  following  apparatus  for  the  continuous  electrolysis 
of  aluminium  chloride  : — * 

The  bed  of  a  reverberatory  furnace  is  divided  by  transverse 
partitions  into  two  compartments,  in  each  of  which  are  two  retorts 
semi-circular  in  section,  lying  side  by  side  horizontally  across  the 
furnace,  with  the  circular  part  up.  They  are  supported  on  refrac- 
tory pillars  so  that  their  open  side  is  a  small  distance  above  the 
floor  of  the  furnace.  The  aluminium  compound  being  melted  on 
the  hearth,  it  stands  to  the  same  depth  in  both  retorts,  and  if  the 
electrodes  are  passed  through  the  bottom  of  the  hearth  they  may 
remain  entirely  submerged  in  molten  salt  and  each  under  its  own 
retort  cover.  The  metal  therefore  collects  in  a  liquid  state  under 

*  German  Patent  (D.  R.  P.),  No.  34728. 


REDUCTION    BY    THE    USE*  OF    ELECTRICITY.  273 

one  retort  and  the  chlorine  under  the  other,  both  being  preserved 
from  contact  or  mixture  with  the  furnace  gases  by  the  lock  of 
molten  salt.  The  chlorine  can  thus  be  led  away  by  a  pipe,  and 
utilized,  while  the  aluminium  collects  without  loss,  and  is  removed 
at  convenient  intervals. 


Henderson's  Process  (1887). 

A.  C.  Henderson,  of  Dublin,*  patents  the  process  of  fluxing 
alumina  with  cryolite,  the  bath  being  put  into  a  graphite  crucible, 
which  serves  as  the  negative  electrode,  and  which  is  put  inside  a 
larger  crucible  and  the  space  between  filled  with  graphite.  The 
positive  electrode  is  of  carbon  and  dips  into  the  fused  material. 
A  current  of  only  3  volts  is  used,  and  the  dissolved  alumina  only 
is  decomposed,  the  cryolite  remaining  unaltered.  The  aluminium 
collects  in  the  bottom  of  the  crucible,  and  as  the  operation  pro- 
ceeds alumina  is  added  to  renew  the  bath.  To  prepare  alloys, 
a  negative  electrode  is  made  of  the  metal  and  used  in  a  similar 
position  to  the  positive  electrode,  and  as  the  current  passes  the 
alloy  is  formed  and  falls  melted  to  the  bottom  of  the  crucible. 

We  must  give  Mr.  Henderson  credit  for  having  introduced  the 
idea  of  decomposing  alumina  held  in  solution  in  a  fused  bath,  an 
idea  which  is,  however,  more  fully  developed  by  Hall  (see  p.  288) ; 
and  also  for  hitting  what  Hampe  designates  as  the  best  mode  of 
procedure  for  obtaining  alloys  in  such  processes  (see  p.  286).  It 
is  to  be  regretted  that,  having  such  a  good  beginning,  we  have  not 
heard  more  of  Mr.  Henderson's  process  in  the  three  years  since  it 
was  patented. 

Bernard  Bros.'  Process  (1887). 

Messrs.  M.  and  E.  Bernard,  of  Paris,  have  patented  a  processf 
which  consists  in  electrolyzing  a  mixture  of  sodium  chloride  with 
aluminium  fluoride  or  with  the  separate  or  double  fluorides  of 
aluminium  and  sodium,  melted  in  a  non-metallic  crucible  or  in  a 


is 


*  English  Patent,  No.  7426  (1887). 

f  English  Patent,  No.  10057,  July  18,  1887. 


274  ALtJMINIUM. 

metallic  one  inclosed  in  a  thin  refractory  jacket  to  avoid  filtration. 
The  details  of  the  apparatus  and  bath  are  as  follows  :— 

Disposition  of  the  Apparatus. — The  pots  or  crucibles  used  may 
be  of  refractory  earth,  plumbago  or  of  metal,  and  in  cases  where 
an  alloy  is  required  the  crucible  itself  serves  as  an  electrode. 
None  of  these,  however,  resist  the  corrosive  power  of  the  electro- 
lyte and  would  under  ordinary  conditions  be  quickly  destroyed. 
To  overcome  this  difficulty  two  special  devices  are  employed. 
When  alloys  are  to  be  made  directly,  the  pot  is  cast  of  the  metal 
with  which  the  aluminium  is  to  be  combined.  It  is  shaped  with 
a  sloping  bottom  and  provided  with  a  tap  hole.  The  pot  is  en- 
cased in  thin  brickwork  and  is  then  made  the  negative  electrode, 
the  positive  being  two  carbon  rods  dipping  into  the  bath.  As 
soon  as  the  current  is  passed  aluminium  is  deposited  on  the  walls 
of  the  pot,  forming  a  rich  alloy  with  the  metal  of  which  the  pot 
is  made  (iron  or  copper).  When  this  coating  becomes  sufficiently 
rich  in  aluminium,  the  heat  of  the  bath  melts  it  and  it  trickles 
down  and  collects  at  the  bottom.  After  a  certain  time,  the  alloy 
can  be  tapped  out  regularly  at  intervals  without  interrupting  the 
electrolysis.  The  metal  thus  obtained  is  principally  aluminium 
containing  a  few  per  cent,  of  the  metal  of  the  pot,  which  is  of  no 
consequence  since  the  end  to  be  finally  attained  is  the  production 
of  an  alloy  with  a  smaller  quantity  of  aluminium.  When  pure 
aluminium  is  to  be  obtained,  an  ingenious  device  is  used  to  pro- 
tect the  metal  from  contamination  by  the  metal  of  the  pot.  Two 
carbon  rods  serve  as  anode  and  cathode,  the  cathode  standing  up- 
right in  a  small  crucible  placed  upon  a  plate  resting  on  the  bottom 
of  the  pot.  This  crucible  and  plate  are  made  from  carbon  blocks 
or  from  fused  alumina  or  fluorspar  moulded  into  the  shape  de- 
sired. As  the  metal  is  set  free  it  trickles  down  the  cathode  and 
is  caught  in  the  crucible  or  cup,  thus  being  prevented  from 
spreading  out  over  the  bottom  of  the  pot.  To  prevent  the  bath 
from  corroding  the  pot,  a  wire  is  passed  from  the  latter  to  the 
negative  pole  of  the  battery.  The  pot  is  thus  made  part  of  the 
negative  electrode,  but  it  is  not  intended  that  much  of  the  current 
should  pass  through  it,  so  a  resistance  coil  is  interposed  between  it 
and  the  battery  or  dynamo,  so  that  the  derived  current  passing 
through  the  sides  of  the  pot  is  only  5  to  10  per  cent,  of  the  whole 


REDUCTION    BY   THE   USE   OF   ELECTRICITY.  275 

current.  The  effect  of  this  is  that  a  small  amount  of  aluminium 
is  deposited  on  and  alloys  with  the  sides  of  the  vessel,  which 
protects  the  latter  from  corrosion  and  is  only  feebly  acted  upon 
by  the  bath.  The  metal  deposited  in  the  crucible  is  thus  kept 
nearly  pure,  while  a  small  amount  of  alloy  falls  to  the  bottom  of 
the  pot  and  is  poured  out  after  the  crucible  has  been  removed. 
When  it  is  wished  to  obtain  the  purest  aluminium,  the  intensity 
of  the  derived  current  passing  through  the  pot  is  increased  by 
removing  part  of  the  resistance  interposed  between  it  and  the 
negative  wire,  thus  also  decreasing  the  intensity  of  the  principal 
current.  The  nature  of  the  electrodes  proper  may  be  varied. 
For  producing  pure  aluminium  the  anode  is  carbon,  the  cathode 
carbon  and  the  pot  either  of  copper  or  iron  ;  for  producing  copper 
alloys  the  anode  may  be  either  carbon  or  bright  copper,  and  the 
cathode  (pot)  of  carbon  or  copper ;  for  producing  iron  alloys  the 
anode  may  be  either  carbon  or  iron,  while  the  vessel  used  as 
cathode  is  either  of  cast-iron  or  plumbago. 

Composition  of  the  bath. — The  proportions  of  the  different  salts 
used  for  the  bath  vary  between  30  to  40  per  cent,  of  fluorides  of 
aluminium  and  of  sodium  and  60  to  70  per  cent,  of  sodium  chlor- 
ide. Very  good  results  are  reported  with — 

Aluminium  fluoride        .......     40 

Sodium  chloride     ........     60 

100 

Pure  cryolite  may  be  used,  mixed  with  varying  quantities  of 
sodium  chloride.  Moreover,  the  separate  fluorides  of  aluminium 
and  sodium  can  be  used  in  different  proportions  to  those  in  which 
they  are  found  in  cryolite ;  for  instance — 

Aluminium  fluoride        .......     35 

Sodium  fluoride      ........     10 

"       chloride 55 

100 

As  aluminium  is  removed,  the  bath  becomes  poor  in  aluminium 
fluoride,  and  this  salt  must  be  added  to  keep  up  its  strength.  For 
each  kilo  of  aluminium  produced  about  3  kilos  of  aluminium 
fluoride  would  need  to  be  added,  but  only  1J  kilos  is  added  as 


276  ALUMINIUM. 

such,  the  other  1 J  kilos  being  regenerated  by  causing  the  fluorine 
vapors  evolved  to  act  on  alumina  or  beauxite  placed  somewhere 
about  the  anode.  The  materials  used,  then,  for  producing  100 
kilos  of  aluminium  are  estimated  as — 

Aluminium  fluoride        .         .  .         .         .     150  kilos. 

Commercial  alumina      ......     200     " 

Sodium  chloride     .         .         .         .         .;       .         .     100     " 

Power  required. — M.  Ad.  Minet,  who  has  written  a  sketch  of 
Bernard's  process  as  carried  out  at  their  works  at  Creil  (Oise), 
maintains  that  aluminium  fluoride  is  the  principal  electrolyte. 
The  bath  is  very  fluid  and  the  temperature  and  composition  kept 
constant  during  the  operation,  the  laws  of  electrolysis  can  there- 
fore be  applied  easily  to  the  discussion  of  the  process.     M.  Minet 
states  that  the  electro-motive  force  absorbed  by  the  bath  is  from 
4  to  5  volts,  and  that  this  is  not  much  above  the  minimum  poten- 
tial necessary  to  decompose  aluminium  fluoride,  deduced  from  its 
heat  of  formation,  which  is  3J  volts.     I  confess  that  I  do  not 
know  of  any  determination  of  this  heat  of  formation  referred  to ; 
we  can  probably  draw  the  inference  that  it  is  greater  than  that 
of  aluminium  chloride,  but  I  do  not  know  that  its  exact  value 
has  been  determined.    Taking,  however,  Minet's  figure  of  3J  volts, 
the  current  is  certainly  very  economically  applied  if  decomposition 
is  produced  with  4  volts.     With  3J  volts  tension,  a  current  of  1 
horse-power  should  produce  72  grammes  of  aluminium  per  hour. 
It  is  stated  that  25  grammes  are  produced  per  hour  per  indicated 
mechanical  horse-power,  which  shows  that  the  aluminium  pro- 
duced represents  a  quantity  of  energy  equal  to  35  per  cent,  of  the 
power  of  the  engine.     Assuming  that  20  per  cent,  of  the  engine 
power  is  lost  in  being  converted  into  electric  energy,  we  have  only 
56  per  cent,  of  the  electric  current  not  productive,  including  the 
loss  by  transfer  resistance  of  the  bath.     Since  5  volts  are  absorbed 
by  the  bath  altogether,  the  amount  lost  by  resistance  is  to  the 
amount  utilized  in  decomposition  as  1 J  to  3J,  which  would  show 
the  former  item  to  be  (100 — 56)  x  f  or  19  per  cent,  of  the  energy 
of  the  current.     This  loss  is  unavoidable,  and  as  small  as  can  be 
well  expected,  so  that  the  real  loss  in  working  is  56 — 19  or  37 
per  cent.     This  is  caused  principally  by  re-solution  of  aluminium 


DEDUCTION   BY   THE   USE   OF   ELECTRICITY.  277 

in  the  bath.  We  might  reach  this  conclusion  by  another  way. 
One  horse-power  furnished  by  the  engine  would  produce  0.8 
electric  horse-power,  which  at  a  tension  of  5  volts  would  furnish 
120  amperes.  According  to  Faraday's  law,  120  amperes  would 
set  free  40  grammes  of  aluminium  per  hour.  As  only  25  were 
obtained  practically,  it  shows  that  15  grammes  have  been  pro- 
duced and  re-dissolved  by  the  bath,  making  this  loss  37.5  per 
cent.  From  the  figures  furnished,  we  see  that  to  produce  100 
kilos  of  aluminium  in  20  hours  would  require  an  engine  of  200 
horse-power,  and  since  each  pot  produces  4  kilos  of  pure  metal  or 
6  kilos  of  aluminium  in  alloys,  per  hour,  a  plant  of  this  output 
would  require  25  pots  for  making  pure  aluminium  or  18  for 
working  on  alloys. 

Quality  of  metal. — When  working  for  pure  aluminium,  about 
three-fourths  of  the  metal  produced  is  taken  from  the  crucible  in 
which  the  cathode  stands,  and  is  98  to  99  per  cent,  pure ;  the 
other  one-fourth  has  been  deposited  on  the  sides  of  the  cast-iron 
pot,  and  contains  10  to  20  per  cent,  of  iron.  It  is  poured  out 
and  used  for  making  ferro-aluminium. 

Reactions  in  the  process. — M.  Minet  claims  that  aluminium 
fluoride  is  the  chief  electrolyte,  since  the  yield  of  aluminium  in- 
creased with  the  proportion  of  this  salt  in  the  bath.  However, 
on  reviewing  this  gentleman's  statements,  we  find  that  when  the 
bath  contains — 

Aluminium  fluoride        .......     40 

Sodium  chloride      ........     60 

100 

the  best  results  are  obtained.  It  is  conceivable  that  the  yield  of 
aluminium  increases  with  the  proportion  of  aluminium  fluoride 
up  to  this  point,  but  there  is  no  reason  for  saying  that  a  further 
increase  would  give  a  better  yield  if  this  has  been  found  the  best 
mixture.  Mr.  Rogers  found  that  when  the  proportion  of  alu- 
minium fluoride  to  sodium  fluoride  in  an  electrolytic  bath  was 
greater  than  40  to  60  (the  proportions  in  which  they  exist  in 
cryolite)  the  resistance  increased  very  materially,  from  which  he 
concluded  that  pure  aluminium  fluoride  is  not  an  electrolyte 
(p.  283).  Further,  Mr.  Hall  has  found  that  when  making  a  bath  of 


278  ALUMINIUM. 

Aluminium  fluoride        .......     67 

Sodium  fluoride      .  33 

100 

it  was  hardly  possible  to  pass  a  current  through  it,  but  on  adding 
alumina  the  latter  dissolved  in  the  bath  and  was  easily  decora- 
posed  by  a  current  of  low  tension;  however,  as  soon  as  the 
alumina  was  exhausted,  the  resistance  rose  quickly.  It  seems 
probable  that  sodium  chloride,  in  Bernard's  process,  is  the  chief 
electrolyte,  or  else  its  combination  with  aluminium  fluoride  in 
certain  proportions,  but  that  the  aluminium  fluoride  is  the  electro- 
lyte is  hardly  probable. 

Messrs.  Bernard  exhibited  at  the  recent  Paris  Exposition  a 
collection  of  articles  made  of  their  metal,  such  as  round  tubes, 
medals,  keys,  opera-glasses,  ingots,  etc.,  for  which  they  received 
the  same  reward  as  the  other  exhibitors  of  aluminium — a  gold 
medal. 

Feldman's  Method  (1887).  • 

A.  Feldman,  of  Linden,  Hannover,  patented  the  following 
electrolytic  process  : — * 

A  double  fluoride  of  aluminium  and  an  alkaline  earth  metal, 
mixed  with  an  excess  of  a  chloride  of  the  latter  group,  is  either 
electrolyzed  or  reduced  by  sodium.  The  proportions  of  these 
substances  to  be  used  are  such  as  take  place  in  the  following 
reactions : — 

1.  (Al2F6+2SrF2)+6SrCl2=  2Al+5SrF2-f3SrCl2+6Cl. 

2.  (Al2F«-f  2SrFa)+6SrCl2-f6Na=  2Al+5SrF2+3SrCl2+6ISTaCl. 

The  three  equivalents  of  strontium  chloride  are  found  in  practice 
to  be  most  suitable.  Potassium  chloride  may  also  be  added  to 
increase  the  fluidity,  but  in  this  case  the  strontium  chloride  must 
be  in  still  greater  excess. 

Even  if  the  above  reactions  and  transpositions  do  take  place, 
the  use  of  so  much  costly  strontium  salts  would  appear  to  render 
the  process  uneconomical. 

*  English  Patent,  No.  12575,  Sept.  16,  1887. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  279 

Warren's  Experiments  (1887). 

Mr.  H.  Warren,  of  the  Everton  Research  Labofatory,  has 
outlined  the  following  methods  or  suggestions,  some  of  which 
had  already  been  carried  out,  and  probably  others  have  since 
given  useful  ideas  to  workers  in  this  line.  The  principle  can 
hardly  be  called  new,  since  suggestions  almost  identical  with 
Mr.  Warren's  were  made  previously  to  his,  but  the  latter's  results 
are  the  first  recorded  in  this  particular  direction  :*  "  This  method 
of  preparing  alloys  differs  only  slightly  from  the  manner  in 
which  amalgams  of  different  metals  are  prepared,  substituting  for 
mercury  the  metals  iron,  copper,  or  zinc  made  liquid  by  heat. 
These  metals  are  melted,  connected  with  the  negative  pole  of  a 
battery,  and  the  positive  pole  immersed  in  a  bath  of  molten  salt 
floating  on  top  of  the  melted  metal.  The  apparatus  used  is  a 
deep,  conical  crucible,  through  the  bottom  of  which  is  inserted  a 
graphite  rod,  projecting  about  one  inch  within,  the  part  outside 
being  protected  by  an  iron  tube  coated  with  borax.  As  an  ex- 
ample of  the  method,  to  prepare  silicon  bronze-copper  is  melted 
in  the  crucible,  a  bath  of  potassium  silico-fluoride  is  fused  on  top 
to  a  depth  of  about  two  inches.  A  thick  platinum  wire  dips  into 
this  salt,  and  on  passing  the  electric  current  an  instantaneous  action 
is  seen,  dense  white  vapors  are  evolved  and  all  the  silicon,  as  it 
is  produced,  unites  with  the  copper,  forming  a  brittle  alloy.  Cryo- 
lite may  be  decomposed  in  like  manner  if  melted  over  zinc,  form- 
ing an  alloy  of  zinc  and  aluminium  from  which  the  zinc  can  be 
distilled  leaving  pure  aluminium." 

Mr.  Warren  does  not  affirm  that  he  has  actually  performed  the 
decomposition  of  cryolite  in  the  way  recommended,  but  states 
that  it  may  be  done ;  from  which  we  would  infer  that  he  simply 
supposed  it  could.  A  well-recorded  experiment,  then,  is  needed 
to  establish  the  truth  of  this  statement.  Neither  does  he  propose 
to  make  aluminium  bronze  in  this  way;  it  may  be  that  it  was 
attempted  and  did  not  succeed,  for  Hampe  states  that  an  experi- 
ment thus  conducted  did  not  furnish  him  aluminium  bronze 
(p.  283). 

*  Chemical  News,  Oct.  7,  1887. 


280  ALUMINIUM. 

BognsWs  Patent. 

J.  Bognski,*  of  Warsaw,  Russia,  appears  to  have  patented  the 
above  principle  in  1884,  for  in  his  patent  he  states  that  the  metal 
to  be  alloyed  with  aluminium  is  melted  in  a  crucible,  covered 
with  a  fusible  compound  of  aluminium  for  a  flux  (alumina  and 
potassium  carbonate  may  be  used)  and  made  the  negative  pole  of 
an  electric  current,  the  positive  pole  being  a  carbon  rod  dipping 
in  the  flux. 

Grabau's  Apparatus. 

Ludwig  Grabau,f  of  Hanover,  Germany,  proposes  to  electro- 
lyze  a  molten  bath  of  cryolite  mixed  with  sodium  chloride.  The 
features  of  the  apparatus  used  are  an  iron  pot,  in  which  the  bath 
is  melted,  and  water-cooled  cylinders  surrounding  both  electrodes, 
the  jacket  surrounding  the  negative  one  having  a  bottom,  the 
other  not.  The  object  of  these  cylinders  is,  at  the  positive  elec- 
trode, to  keep  the  liberated  fluorine  from  attacking  the  iron  pot 
and  so  contaminating  the  bath,  at  the  other  pole  the  liberated 
aluminium  is  kept  from  dropping  to  the  bottom  of  the  pot,  where 
it  might  take  up  iron,  and  can  be  removed  from  the  bath  by 
simply  lifting  out  the  water-cooled  cylinders  and  carbon  electrode. 
Mr.  Grabau  states  that  he  has  abandoned  this  process  because  the 
inseparable  impurities  in  the  cryolite  produced  impurities  in  the 
metal ;  it  may  be  that  with  the  pure  artificial  cryolite,  which  he 
makes  by  his  other  processes  (see  p.  139),  this  electrolytic  process 
may  again  be  taken  up. 

Rogers'  Process  (1887). 

In  July,  1887,  the  American  Aluminium  Company,  of  Mil- 
waukee, was  incorporated,  with  a  capital  stock  of  $1,000,000,  for 
the  purpose  of  extracting  aluminium  by  methods  devised  by 
Prof.  A.  J.  Rogers,  a  professor  of  chemistry  in  that  city.  This 
gentleman  had  been  working  at  the  subject  for  three  or  four 

*  English  Patent  3090,  Feb.  11,  1884. 
f  German  Patent  (D.  R.  P.),  No.  45012. 


REDUCTION   BY  THE   USE   OF   ELECTRICITY.  281 

years  previous  to  that  time,  but  it  has  not  been  until  quite  recently 
that  patents  have  been  applied  for,  and  they  are  still  pending. 

The  principle  made  use  of  has  already  been  suggested  in  con- 
nection with  the  production  of  sodium  (p.  183).  It  is  briefly,  that 
if  molten  sodium  chloride  is  electrolyzed  using  a  molten  lead 
cathode,  a  lead-sodium  alloy  is  produced.  This  alloy  is  capable 
of  reacting  on  molten  cryolite,  setting  free  aluminium,  which  does 
not  combine  with  the  lead  remaining  because  of  its  small  affinity 
for  that  metal.  If,  then,  cryolite  is  placed  in  the  bath  with  the 
sodium  chloride,  the  two  reactions  take  place  at  once,  and  alu- 
minium is  produced.  In  the  early  part  of  1888,  the  company 
erected  a  small  experimental  plant,  with  a  ten  horse-power  engine, 
with  which  the  following  experiments,  among  many  others,  were 
made : — 

*1.  A  current  of  60  to  80  amperes  was  passed  for  several  hours 
through  a  bath  of  cryolite  melted  in  a  crucible  lined  with  alu- 
mina, and  using  carbon  rods  2J  inches  in  diameter  as  electrodes, 
one  dipping  into  the  bath  from  above,  the  other  passing  through 
the  bottom  of  the  crucible  into  the  bath.  Only  1  or  2  grammes 
of  aluminium  were  obtained,  showing  that  the  separated  metal 
was  almost  all  redissolved  or  reunited  with  fluorine.  With  the 
temperature  very  high,  it  was  found  that  sodium  passed  away 
from  the  bath  without  reducing  the  cryolite.  . 

2.  A  current  averaging  54  amperes  and  10  volts  was  passed 
for  five  and  a  half  hours  through  a  mixture  of  1  part  cryolite 
and  5  parts  sodium  chloride  placed  in  a  crucible  with  370 
grammes  of  molten  lead  in  the  bottom  as  the  cathode.  After  the 
experiment,  25  grammes  of  aluminium  were  found  in  globules  on 
top  of  the  lead-sodium  alloy.  This  latter  alloy  contained  some 
aluminium.  The  globules  were  about  as  pure  as  ordinary  com- 
mercial aluminium  and  contained  no  lead  or  sodium.  From 
another  experiment  it  was  determined  that  the  lead-sodium  alloy 
must  first  acquire  a  certain  richness  in  sodium  before  it  will  part 
writh  any  of  that  metal  to  perform  the  reduction  of  the  cryolite. 
It  was  also  found  that  a  certain  temperature  was  necessary  in 
order  that  aluminium  be  produced  at  all. 

*  Proceedings  of  the  Wisconsin  Nat.  Hist.  Soc.,  April,  1889. 


282  ALUMINIUM. 

3.  A  current  of  75  amperes  and  about  5  volts  sufficed  to  de- 
compose the  bath  and  to  produce  105  grammes  of  aluminium  in 
seven  hours.     This  would  be  nearly  30  grammes  per  hour  for 
each  electric  horse-power. 

4.  A  current  of  80  amperes  and  24  volts  was  passed  through 
four  crucibles  connected  in  series  for  six  hours,  using  a  bath  of  1 
part  cryolite  and  3  parts  sodium  chloride  with  450  grammes  of 
lead  in  each  crucible.     The  crucibles  were  heated  regularly  to 
a  moderate   temperature.     There  were  obtained  altogether  250 
grammes  of  quite  pure  aluminium.     This  would  be  equal  to  16 
grammes  per  electric  horse-power-hour. 

A  large  number  of  similar  experiments  afforded  a  return  of  f 
to  1 J  Ibs.  of  aluminium  per  electric  horse-power  per  day.  The 
experimental  plant  now  in  operation  consists  of  a  40  volt — 100 
ampere  dynamo,  the  current  being  sent  through  six  pots  connected 
in  series.  When  the  bath  is  completely  electrolyzed  the  contents 
of  the  crucible  are  tapped  off  at  the  bottom  and  a  fresh  supply  of 
melted  salt  poured  in  quickly.  The  lead-sodium  alloy  run  off  is 
put  back  into  the  crucibles,  thus  keeping  approximately  con- 
stant in  composition  and  going  the  rounds  continuously.  With  this 
apparatus,  3  to  4  Ibs.  of  aluminium  are  produced  regularly  per 
day  of  12  hours.  As  soon  as  patents  are  obtained,  it  is  the  in- 
tention of  the  company  to  put  up  a  plant  of  50  Ibs.  daily  capacity 
which  can  be  easily  increased  to  any  extent  desired  as  the  business 
expands. 

Professor  Rogers  observes  in  regard  to  the  apparatus  that  he 
has  tried  various  basic  linings  for  his  clay  crucibles,  but  a  paste 
of  hydrated  alumina,  well  fired,  has  succeeded  best.  Some 
"  shrunk"  magnesia  lining,  such  as  is  used  in  basic  steel  furnaces, 
answered  well  but  could  not  be  used  because  of  the  amount  of 
iron  in  it.  Lime  could  not  be  used,  as  it  fluxed  readily.  The 
carbon  rods  lasted  48  hours  without  much  corrosion  if  protected 
from  the  air  during  electrolysis.  Carbon  plates  and  cylinders 
were  tried,  but  the  solid  rods  gave  the  best  results.  About  8  to  10 
per  cent  of  aluminium  can  be  extracted  from  cryolite  containing 
12.85  per  cent.  The  mineral  used  was  obtained  from  the  Penn- 
sylvania Salt  Company,  and  was  called  pure,  but  it  contained  2 
per  cent,  of  silica  and  1  per  cent,  ot  iron.  These  impurities  pass 


KEDUCTION    BY   THE   USE   OF   ELECTRICITY.  283 

largely  into  the  aluminium  produced,  but  the  company  hope  to  be 
able  to  manufacture  an  artificial  aluminium  fluoride  which  will 
not  only  be  purer  but  less  costly  than  this  commercial  cryolite. 
Professor  Rogers  infers  that  pure  aluminium  fluoride  would  not 
be  an  electrolyte,  since  the  resistance  of  the  bath  increases  as  the 
amount  of  other  salts  present  decreases. 

It  is  useless  to  base  any  accurate  estimation  of  the  cost  of  alu- 
minium by  this  process  on  the  data  given  above,  since  they  are 
only  for  a  small  experimental  plant.  If,  however,  75  per  cent. 
of  the  aluminium  in  cryolite  can  be  extracted  at  the  rate  of  1  Ib. 
of  metal  per  day  per  electric  horse-power,  and  the  metal  is  free 
from  lead  and  sodium,  (a  sample  sent  me  recently  is  of  very  fair 
quality)  it  would  seem  that  the  process  is  in  a  fair  way  to  com- 
pete on  an  equal  footing  with  the  other  electrolytic  processes 
which  are  coming  into  prominence. 

Dr.  Hampe  on  the  Electrolysis  of  Cryolite. 

• 

Prof.  W.  Hampe,  of  Clausthal,  whose  name  is  a  guarantee  of 
careful  and  exact  observations,  has  written  the  following  valuable 
information  on  this  subject,  in  presenting  which  we  will  also  give 
the  remarks  of  Dr.  O.  Schmidt,  called  forth  by  Hampe's  first 
article. 

*"The  electrolysis  of  a  bath  of  cryolite  mixed  with  sodium 
and  potassium  chlorides,  using  a  layer  of  melted  copper  in  the 
bottom  of  the  crucible  as  cathode  and  a  carbon  rod  as  anode,  gave 
balls  of  melted  sodium  which  floated  on  the  surface  and.  burnt, 
but  scarcely  a  trace  of  aluminium.  Yet  here  the  conditions  were 
most  favorable  to  the  production  of  the  bronze.  The  battery 
used  consisted  of  twelve  large  zinc-iron  elements." 

fDr.  O.  Schmidt,  referring  to  this  statement  of  Hampers,  quotes 
an  opposite  experience.  He  fused  cryolite  and  sodium  chloride 
together  in  a  well-brasqued  crucible  in  the  proportions  indicated 
by  the  reaction 

Al'F'.GNaF  +  6NaCl  =  APC16  +  12NaF. 

At  a  clear  red-heat  the  bath  becomes  perfectly  fluid  and  trans- 
parent, and  an  anode  of  gas  carbon  and  a  cathode  of  sheet  copper 


Chemiker  Zeitung,  xii.  391   (1888).  f  ^em,  xii.  457  (1888). 


284  ALUMINIUM. 

are  introduced.  On  passing  the  current  the  copper  did  not  melt 
but  became  covered  with  a  film  of  deposited  aluminium,  which  in 
part  penetrated  the  electrode  and  in  part  adhered  to  the  surface 
as  a  rich  alloy  which  utimately  fused  off  and  sank  to  the  bottom 
of  the  crucible.  With  a  plate  1  to  1J  millimetres  thick,  10  per 
cent,  of  its  weight  of  aluminium  could  thus  be  deposited  ;  with 
one  3  millimetres  thick,  about  5  per  cent.  The  metal  could  be 
made  perfectly  homogeneous  by  subsequent  fusion  in  a  graphite 
crucible.  Dr.  Schmidt  further  remarks  (evidently  on  the  sup- 
position that  the  reaction  he  gives  actually  takes  place)  that  on 
thermo-chemical  grounds  sodium  would  not  here  be  reduced,  be- 
cause while  the  molecule  of  sodium  chloride  requires  97.3  calories 

APC16 
for  its  decomposition,  that  of  aluminium  chloride, ,  requires 

2> 

only  80.4,  and  the  current  would  attack  first  the  most  easily  de- 
composed. He  also  states  that  the  calculated  difference  of  poten- 
tial for  the  dissociation  of  aluminium  chloride,  which  is  — L-  = 

2i& 

3.5  volts,  was  actually  observed,  and  the  tension  of  the  current 
must  have  been  increased  to  about  4.5  volts  to  bring  about  the 
decomposition  of  the  sodium  chloride.* 

Dr.  Hampers  statement  occasioned  several  other  communica- 
tions, which  he  considers  and  replies  to  in  the  following  arti- 
cle :— f 

*  Aside  from  Hampe's  subsequent  remarks  as  to  no  aluminium  chloride 
being  formed,  we  would  further  point  out  the  fact  that  the  decomposition  of  a 

chemically  equivalent  quantity  of  aluminium  chloride  requires  not  — -1~  = 

2 

00*1    f?O(\ 

80.4  calories,  but ! or   53.6  calories,  and   the  calculated  difference  of 

6 

RO     {• 

potential  is  properly  * 1_  or  2.3  volts.     The  fact  that  the  observed  tension 

23 

was  3.5  volts  shows  that  the  current  was  not  strong  enough  to  decompose  the 
sodium  chloride,  as  Schmidt  observes,  and  the  fact  that  this  current  deposited 
aluminium  would  show  that  the  heat  of  formation  of  aluminium  fluoride  can- 
iiot  be  greater  than  23  X,3.5  X  6  =483  (thousand)  calories,  while  it  is  pro- 
bably much  less  than  this,  for  the  3.5  volts,  besides  decomposing  the  alu- 
minium compound,  were  also  partly  expended  in  overcoming  resistances,  as 
explained  on  p.  248. 

f  Chemiker  Zeitung  (Cothen)  xiii.  29  and  49. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  285 

"  Dr.  O (whose  Dame  I  withhold  at  his  own  request)  writes 

to  me  that  by  electrolyzing  pure  cryolite,  using  a  negative  pole  of 
molten  copper,  he  never  obtained  aluminium  bronze ;  but,  on  the 
other  hand,  always  obtained  it  if  he  used  the  mixture  of  cryolite 
and  sodium  chloride  mentioned  by  Dr.  Schmidt,  and  in  place  of 
the  molten  copper  a  thick  stick  of  the  unfused  metal.  A  letter 
from  R.  Gratzel,  Hannover,  contains  a  similar  confirmation  of  the 
latter  observation.  By  electrolyzing  a  mixture  of  100  parts  cryo- 
lite with  150  of  sodium  chloride  in  a  graphite  crucible  holding  30 
kilogrammes,  aluminium  bronze  dripped  down  from  the  ring- 
shaped  copper  cathode  used,  while  chlorine  was  freely  disengaged 
at  the  carbon  anode.  But  after  a  time,  long  before  the  complete 
decomposition  of  the  cryolite,  the  formation  of  bronze  stopped—- 
even an  attacking  of  that  already  formed  sometimes  taking  place. 
Pellets  of  an  alloy  of  sodium  and  aluminium  appear  on  the  sur- 
face and  burn  with  a  white  light. 

"  These  comments  excited  me  to  further  research  in  the  matter. 
At  first,  it  was  necessary  to  consider  or  prove  whether  by  melting 
sodium  chloride  with  cryolite  a  true  chemical  decomposition  took 
place,  such  as  Dr.  Schmidt  supposed.  If  this  were  the  case,  the 
very  volatile  aluminium  chloride  must  necessarily  be  mostly 
driven  off  on  melting  the  mixture,  and  at  a  temperature  of  700° 
to  1000°  C.  there  could  not  be  any  left  in  it.  But  an  experiment 
in  a  platinum  retort  showed  that  such  a  reaction  positively  does 
not  occur ;  for  neither  was  any  aluminium  chloride  volatilized  nor 
did  the  residue  contain  any,  for  on  treatment  with  water  it  gave  up 
no  trace  of  a  soluble  aluminium  compound.  During  the  melting 
of  the  mixture  acid  vapors  proceeded  from  the  retort,  and  a  small 
quantity  of  cryolite  was  volatilized  into  the  neck  of  the  retort. 
Dr.  Klochman  has  shown  that  cryolite  always  contains  quartz, 
even  colorless,  transparent  pieces  which  to  the  naked  eye  appear 
perfectly  homogeneous  showing  it  when  examined  in  thin  sections 
under  the  microscope,  and  on  melting  the  mineral  opportunity  is 
given  for  the  following  reactions  : — 

SiO2  4-  4NaF= SiF4  +  2Na2O, 
3Na2O  +  A12F6  =  6NaF  +  A12O3, 

as  is  rendered  probable  by  the  appearance  of  delicate  crystals  of 
alumina  on  the  inner  surface  of  the  retort  just  above  the  fusion. 


286  ALUMINIUM. 

The  silicon  fluoride  probably  passes  away  as  silico-fluoride  ol 
sodium. 

"  If  cryolite  is  fused  with  such  metallic  chlorides  that  really  do 
bring  about  a  decomposition,  there  is  never  any  aluminium  chlor- 
ide formed  in  these  cases,  but  the  sodium  of  the  cryolite  is  ex- 
changed for  the  other  metal.  Dr.  O ,  to  whom  I  owe  this 

observation,  fused  cryolite  with  calcium  chloride,  hoping  that 
aluminium  chloride  would  distil,  but  obtained  instead  crystals  of 
the  calcium  salt  of  alumino-fluoric  acid ;  thus, 

ISa'APF12  +  3CaCl2 = 6NaCl  +  Ca3Al2F12, 

and  in  like  manner  can  be  obtained  the  analogous  strontium  or 
barium  compounds. 

"  Just  as  erroneous  as  the  supposed  production  of  aluminium 
chloride  are  the  other  arguments  advanced  by  Dr.  Schmidt,  re- 
garding the  reasons  why  sodium  could  not  be  set  free.  The  self- 
evident  premises  for  the  propositions  are  lacking,  viz  :  that  the 
two  bodies  compared  are  conductors.  On  the  contrary,  I  have 
previously  shown*  that  aluminium  chloride  and  bromide  and 
more  certainly  its  fluoride  belong  to  the  non-conductors.  It  fol- 
lows, then,  that  there  can  remain  no  doubt  that  on  electrolyzing 
pure  cryolite,  or  a  mixture  of  it  with  sodium  chloride,  only  sodium 
will  be  set  free  at  first,  either  from  sodium  fluoride  or  the  more 
easily  decomposable  sodium  chloride.  The  presence  or  absence 
of  sodium  chloride  is  consequently,  chemically,  without  signifi- 
cance. 

"  Since  the  experiments  with  solid  cathodes  gave  aluminium, 
while  those  with  molten  copper  did  not,  these  results  being  inde- 
pendent of  the  presence  or  absence  of  sodium  chloride,  the  next 
attempt  made  was  to  seek  for  the  cause  of  the  diiferent  re- 
sults in  the  differences  of  temperature.  It  was  found  that  when 
the  electrolysis  takes  place  at  a  temperature  about  the  melting 
point  of.  copper,  bubbles  of  sodium  vapor  rise  and  burn,  and  any 
aluminium  set  free  is  so  finely  divided  that  it  is  attacked  and  dis- 
solved by  the  cryolite.  To  explain  this  action  of  the  cryolite  it  is 
necessary  to  admit  the  formation  of  a  lower  fluoride  of  aluminium 

*  Chemiker  Zeitung  (Cothen)  xi.  p.  934  (1887). 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  287 

and  sodium,  such  as  I  have  recently  proven  the  existence  of.* 
The  solution  of  the  aluminium  takes  place  according  to  the  fol- 
lowing reaction 

APF6.6NaF  -f  Al= 3(AlF2.2NaF.) 

If  the  electrolysis  takes  place  at  a  temperature  so  low  that  the 
sodium  separates  out  as  a  liquid  (its  volatilizing  point  is  about 
900°),  large  globules  of  aluminium  will  be  produced  on  which 
the  cryolite  seems  to  exert  no  appreciable  action.  Nevertheless, 
the  yield  of  aluminium  is  much  below  the  theoretical  quantity  set 
free.  Since  pure  copper  melts  at  1050°,  and  aluminium  bronze  at 
800°,  the  copper  electrodes  can  remain  unfused  in  the  bath  while 
the  bronze  melts  off  as  it  forms,  while  the  temperature  can  be 
low  enough  to  keep  the  sodium  in  the  liquid  state.  By  mixing 
sodium  or  potassium  chlorides  with  the  cryolite,  the  melting  point 
is  lowered,  or  at  a  given  temperature  the  bath  is  more  fluid  and 
so,  easier  to  work.  When  there  is  not  enough  aluminium  fluoride 
present  in  the  bath  to  utilize  all  the  sodium  liberated,  the  excess 
of  sodium  may  form  an  alloy  with  some  aluminium,  and  rising  to 
the  surface,  burn  to  waste.  Since  cryolite  always  contains  silica, 
as  previously  explained,  the  bronze  thus  obtained  is  always  ren- 
dered hard  with  silicon,  and  is  not  of  much  value  commercially/7 

Winkler's  Patent. 

fAugust  Winkler,  of  Gorlitz,  proposes  to  electrolyze  a  fusible 
phosphate  or  borate  of  aluminium.  This  bath  is  made  by  melt- 
ing alumina  or  kaolin  with  phosphoric  or  boracic  acid,  the  pro- 
portions being  such  that  the  acid  is  saturated ;  the  separation  of 
aluminium  will  not  be  hindered  if  alumina  is  added  continually 
to  combine  with  the  acid  set  free.  Carbon  electrodes  are  used. 

*  Chem.  Zeit.  (Cothen)  xiii.  p.  1  (1889).  Hampe  melted  together  alumin- 
ium and  sodium  fluorides  in  the  proportions  of  one  molecule  of  the  first  to 
four  of  the  second,  and  obtained  what  is  apparently  a  lower  fluoride  than  cryo- 
lite, in  which  aluminium  cannot  be  otherwise  than  diatomic,  since  analysis 
gives  it  the  formula  AlFa.2NaP.  This  salt  is  similar  in  appearance  and  prop- 
erties to  cryolite.  As  there  are  still  some  doubts,  however,  about  this  com- 
pound, the  above  explanation  of  the  solution  of  aluminium  by  the  cryolite 
need  not  be  accepted  as  final. 

f-  German  Patent,  45824,  May  15,  1888. 


288  ALUMINIUM. 

Faure's  Proposition. 

Camille  A.  Faure,  whose  process  of  making  aluminium  chlor- 
ide is  described  on  p.  1 34,  proposes  to  obtain  the  metal  therefrom 
by  electrolysis,  using  carbon  electrodes.  M.  Faure  states  that  if 
the  process  is  carried  out  on  a  large  scale  the  chlorine  set  free  can 
be  utilized  to  form  bleaching  powder,  and  will  thus  nearly  repay 
the  whole  cost  of  manufacturing  the  aluminium.  Patents  have 
been  applied  for  covering  the  details  of  the  electrolytic  apparatus, 
but  have  not  yet  been  granted.  The  inventor  states,  however, 
that  he  has  determined  on  a  large  scale  that  anhydrous,  molten 
aluminium  chloride  can  be  practically  decomposed  at  300°  by 
an  electro-motive  force  of  5  volts,  which  comprises  the  force  re- 
quired for  actual  decomposition  and  also  that  required  to  over- 
come the  resistance  of  the  bath.  While,  therefore,  the  reduction 
of  1  kilo  of  aluminium  per  hour  theoretically  requires  a  minimum 
expenditure  of  9.2  electric  horse-power,  the  actual  resistance  of 
5  volts  would  increase  this  requirement  to  20  horse-power  or  9 
horse-power  per  Ib.  produced  per  hour.  Therefore,  if  each  bath 
could  be  decomposed  by  5  volts,  the  production  of  2000  Ibs.  of 
aluminium  in  20  hours  would  require  the  use  of  a  920  horse- 
power current,  and  could  not  be  possibly  achieved  by  a  400  horse- 
power dynamo,  as  calculated  by  M.  Faure. 

Hairs  Process  (1889). 

Mr.  Chas.  M.  Hall,  a  graduate  of  Oberlin  College,  has,  since 
1885,  experimented  with  electrolytic  aluminium  processes,  and  has 
finally  attained  such  success  that  a  company  has  been  formed  to 
work  by  his  methods.  The  Pittsburgh  Reduction  Company  was 
organized  about  the  middle  of  1888,  and  since  March,  1889,  have 
had  their  metal  on  the  market.  They  are  located  on  Fifth  Ave- 
nue, Pittsburgh,  Pa.  The  plant  is  at  present  equal  to  a  produc- 
tion of  about  300  Ibs.  of  aluminium  a  week,  and  their  metal  is 
quoted  at  $2  per  Ib.  Contracts  have  recently  been  given  out  for 
the  erection  of  a  plant  of  2500  Ibs.  weekly  capacity ;  a  plant  of 
the  same  size  is  also  being  erected  at  Patricroft,  Lane.,  England. 

*Mr.  Hall  claims  the  process  of  dissolving  alumina  in  a  fluid 

*  U.  S.  Patents,  400664  to  400667,  and  400766,  April  2,  1889. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  289 

bath  composed  of  aluminium  fluoride  and  potassium  fluoride,  or 
with  also  the  addition  of  lithium  fluoride,  then  electrolyzing  this 
bath  using  an  anode  of  non-carbonaceous  material.  The  bath 
is  formed  by  fusing  a  mixture  of  the  required  fluorides  in  certain 
proportions;  thus,  169  parts  of  aluminium  fluoride  and  116 
parts  of  potassium  fluoride  form  proportions  corresponding  to  the 
formula  A12F6.2KF.  A  slight  variation  from  these  proportions 
affects  the  process  but  little,  but  it  is  observed  that  a  larger  pro- 
portion of  potassium  fluoride  increases  the  capacity  of  the  bath 
for  dissolving  alumina,  while  a  larger  proportion  of  aluminium 
fluoride  renders  the  bath  more  fusible  but  decreases  the  amount 
of  alumina  it  can  dissolve.  However,  the  bath  is  rendered  more 
fusible  and  its  capacity  for  dissolving  alumina  increased  also,  if 
lithium  fluoride  is  added  to  the  above  mixture  or  substituted 
for  part  of  the  potassium  fluoride.  Thus,  the  combinations 
in  proportions  represented  by  the  formulae  Al2F6.KF.LiF  and 
2Al2F6.3KF.3LiF  are  useful  in  both  respects.  These  materials 
may  be  conveniently  prepared  by  saturating  aluminium  hydrate 
and  carbonates  of  potassium  and  lithium,  mixed  in  the  proportion 
required,  with  hydrofluoric  acid.  In  electrolyzing  the  bath,  the 
negative  electrode  is  to  be  of  carbon  or  a  metal  coated  with  carbon 
and  the  positive  electrode  of  copper,  platinum,  or  other  suitable 
non-carbonaceous  material.  When  of  copper,  it  soon  becomes 
coated  with  oxide  of  copper,  which  is  a  conductor  at  a  red  heat, 
and  therefore  does  not  affect  the  passage  of  the  currenij,  while  it 
forms  a  protecting  cover  over  all  the  surface  of  the  anode  and 
prevents  further  oxidation,  the  oxygen  thereafter  escaping  at  this 
electrode  in  a  free  state.  The  containing  vessel  is  of  metal  pro- 
tected by  a  carbon  lining,  which  is  preferably  made  the  negative 
electrode.  A  low  red  heat  is  sufficient  for  carrying  on  the  opera- 
tion, and  on  account  of  the  liability  of  reducing  the  solvent  a 
current  of  low  electro-motive  force  is  used. 

In  the  second  patent,  Hall  claims  the  use  of  a  bath  composed 
of  alumina  dissolved  in  compound  fluorides  of  aluminium  with 
alkaline-earth  metals,  such  as  in  proportions  varying  from  Al2- 
F6.CaF2  to  Al2F6.3CaF2.  Since  this  bath  is  of  higher  specific 
gravity  than  aluminium,  that  metal  would  rise  to  the  surface  and 
there  be  subject  to  loss  by  oxidation ;  to  remedy  which  a  quan- 
19 


290  ALUMINIUM. 

tity  of  the  salt  represented  by  A12F6.2KF  may  be  added  suffi- 
cient to  lower  the  specific  gravity  of  the  bath  below  that  of  alu- 
minium.* If  it  is  desired  to  produce  alloys,  the  metal  to  be 
alloyed  may  be  made  the  negative  electrode,  in  which  case  the 
addition  of  A12F6.2KF  is  unnecessary,  because  the  alloy  will  be 
sufficiently  heavy  to  sink.  For  making  alloys  the  barium  com- 
pound is  especially  recommended,  for  its  high  specific  gravity  is 
of  no  inconvenience,  and  it  is  more  fusible  than  the  compounds 
of  calcium  and  strontium.  These  double  fluorides  are  said  not 
to  be  subject  to  a  decrease  in  efficiency  such  as  occurs  with  the 
double  fluoride  of  potassium  and  aluminium  when  used  alone. 

In  a  third  patent,  the  use  of  a  bath  formed  of  fluorides  of  cal- 
cium, sodium  and  aluminium,  in  which  alumina  is  dissolved,  is 
claimed ;  these  materials  being  obtained  by  melting  together 
cryolite,  aluminium  fluoride  and  fluorspar  in  the  proportions 
represented  by  the  formula  Al2F6.61SraF  +  Al2F6.CaF2.  This 
bath  is  said  not  to  become  so  readily  clogged  as  the  previous 
ones ;  but  when  it  does  become  so  it  is  cleared  by  the  addition  of 
three  or  four  per  cent,  of  calcium  chloride,  and  this  device  is  said 
to  permit  the  use  of  a  carbon  anode  without  the  bath  being 
affected  by  its  disintegration. 

The  plant  now  being  operated  in  Pittsburgh  consists  of  a  50 
horse-power  engine  drwing  two  dynamos  connected  in  parallel, 
the  current  produced  varying  from  1 6  to  25  volts  in  tension  and 
1700  to  1800  amperes  in  quantity.  TAVO  reducing  pots  are 
used,  coupled  in  series.  Each  pot  is  of  cast-iron  lined  with  car- 
bon, the  lining  forming  the  negative  electrode,  while  a  number 
(6  to  10)  of  three-inch  carbon  cylinders  are  suspended  in  the 
bath  and  form  the  positive  electrode.  Each  pot  holds  200  to 
300  pounds  of  the  electrolyte,  its  dimensions  being  24  inches  long, 
16  inches  wide  and  20  inches  deep.  These  vessels  are  not  heated 
from  outside,  as  was  done  in  the  early  stages  of  the  process  when 
a  current  of  only  4  to  6  volts  tension  was  employed,  but  the  dis- 

*  A  specimen  of  the  salt  represented  by  the  formula  A12F6.2KF  was  sent  the 
author,  who  found  its  specific  gravity  to  be  2.35.  I  should  infer  from  analogy 
that  its  specific  gravity  when  molten  would  be  much  less,  probably  not  much 
over  2,  since  solid  cryolite  has  a  specific  gravity  of  2.9,  and  yet,  when  molten, 
a  piece  of  aluminium  of  gravity  2.6  will  sink  beneath  it.  • 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  291 

tance  between  the  electrodes  is  now  increased  until  the  electro- 
motive force  absorbed  in  each  bath  is  8  to  12  volts,  and  enough 
heat  is  thus  generated  by  this  resistance  to  keep  the  bath  at  the 
necessary  temperature.  The  bath  at  present  employed  for  pro- 
ducing pure  aluminium  is  the  last  one  described,  and  the  tempera- 
ture is  continuously  kept  very  near  to  the  melting  point  of  brass, 
sometimes  it  is  hot  enough  to  melt  copper,  but  the  high  tempera- 
ture is  not  a  disadvantage  since  the  bath  is  more  efficient — i  e., 
conducts  better  and  collects  the  aluminium  better — the  hotter  it 
is,  within  certain  limits.  During  the  operation,  alumina  (obtained 
by  calcining  pure  aluminium  hydrate)  is  fed  in  small  quantities 
of  5  to  10  pounds  as  required.  The  exhaustion  of  the  alumina 
in  the  bath  is  immediately  shown  by  a  rise  in  the  resistance,  so 
that  the  current  can  hardly  be  made  to  pass  at  all.  Mr.  Hall 
has  estimated  that  when  the  bath  is  saturated  with  alumina  its 
conducting  power  is  at  least  200  times  that  of  copper  sulphate 
solution.  In  an  experiment  which  he  made,  a  copper  anode  of 
about  30  to  40  square  inches  area  transmitted  as  high  as  150 
amperes  with  an  electro-motive  force  less  than  3J  volts.  Only 
the  dissolved  alumina  is  decomposed  by  the  current,  for  the 
fluoride  solvents  waste  only  very  slightly  and  require  replenishing 
to  the  extent  of  a  small  fraction  of  the  weight  of  metal  made  ; 
and  as  these  materials  cost  only  about  7  cents  a  pound,  their 
waste  forms  a  very  small  item  of  expense.  An  accurate  account 
of  the  amount  of  calcined  alumina  used  shows  that  a  fraction  over 
50  per  cent,  of  aluminium  is  extracted  from  it  (theoretically  pure 
alumina  contains  52.94  per  cent.).  It  is  thus  seen  that  the  process 
is  able  to  extract  nearly  all  the  aluminium  from  commercial  alu- 
mina in  one  direct  operation.  When  it  is  desired  to  form  bronze, 
a  bath  of  different  composition  is  used,  as  before  mentioned,  and 
both  electrodes  are  of  copper.  On  working  at  a  temperature  just 
below  that  of  melting  copper,  the  anode  remains  undissolved  and 
practically  unattacked,  while  the  bronze  formed  at  the  cathode 
drips  down  melted  to  the  bottom  of  the  vessel.  In  either  case 
the  metal  is  allowed  to  collect  in  the  pots  for  one  or  two  days, 
and  is  then  ladled  out  with  cast-iron  ladles,  taking  the  metal  from 
the  bottom  as  one  might  dip  water  out  from  under  oil.  The  pro- 
duction is  about  one  pound  of  aluminium  an  hour  from  each  pot, 


292  ALUMINIUM. 

and  the  operations  are  kept  up  without  stopping  for  several  weeks 
at  a  time.  The  metal  produced  has  varied  from  94  to  over  98 
per  cent.  pure.  Three  analyses  by  Mr.  Hall  have  given — 

i.  ii.  irr. 

Aluminium  ....     94.16  95.93  98.34 

Silicon 4.36  2.01  1.34 

Iron 1.48  2.06  0.32 

The  metal  being  made  at  present  averages  over  97  per  cent.,  and 
a  specimen  kindly  sent  the  author  compares  favorably  with  other 
commercial  brands.  A  specimen  sent  me  at  an  early  stage  of  the 
process  contained  copper,  probably  from  the  copper  anodes,  but 
this  has  since  been  avoided  by  discontinuing  the  use  of  copper 
anodes  in  making  the  pure  aluminium. 

The  essential  features  of  Mr.  HalFs  process  have  been  ante- 
dated ;  the  principle  of  dissolving  alumina  in  a  fluid  bath,  and 
electrolyzing  it  without  decomposing  the  solvent,  is  the  matter  of 
Henderson's  patent  issued  in  1887,  and  Bernard  Bros,  claim  the 
use  of  a  copper  anode  in  their  patent  of  the  same  year  (pp.  273  and 
274).  It  is  only  just  to  Mr.  Hall,  however,  to  observe  that  his 
patent  applications  were  dated  in  1886,  and  that  the  use  of  these 
principles  is  clearly  original  with  him.  If  we  seek  to  find  the 
efficiency  of  the  process,  basing  our  calculations  on  the  data  given, 
we  reach  the  following  results :  The  current  is  said  to  average 
1700  amperes  and  20  volts,  being  10  volts  to  each  pot.  A  cur- 
rent of  this  size  would  represent or  a  little  over  45  elec- 
tric horse-power,  which  would  need  about  a  fifty  horse-power 
engine  to  drive  the  dynamos.  If  the  energy  of  this  current  could 
be  entirely  utilized  for  dissociating  alumina  into  aluminium  and 

1700  x  20  x  0.00024 
oxygen,  it  would  be  able  to  produce  - _  =  11 

grammes  per  second,  or  4  kilos  per  hour.     Since  the  output  is 

stated  as  1  Ib.  per  hour  for  each  pot,  the  production  of  aluminium 

2 
represents  —  or  nearly  one-quarter  of  the  energy  of  the  current, 

8.8 

which  it  is  almost  needless  to  observe,  is  a  high  efficiency  in  this 
kind  of  work.  Further,  a  current  of  1700  amperes  passing 


* 
REDUCTION   BY   THE   USE   OF   ELECTKICITY.  293 

through  two  pots  will  set  free  0.00009135x1700x60x60x2 

=  1008  grammes  of  aluminium  per  hour,  or  about  1  kilogramme. 

2 
This  shows  that  -  -  or  91  per  cent,  of  the  aluminium  set  free  is 

practically  obtained  and  weighed,  the  other  9  per  cent,  being  re- 
dissolved  or  otherwise  lost.  Since  we  have  calculated  that  the 
decomposition  of  alumina  requires  an  electro-motive  force  of  2.8 
volts,  the  fact  that  something  like  10  volts  is  required  for  each 
bath  would  show  that  about  7.2  volts,  or  72  per  cent,  of  the 
energy  of  the  current  is  absorbed  in  other  resistances,  being  prin- 
cipally converted  into  heat,  and  thus  keeping  the  bath  in  fusion. 
As  to  the  probable  cost  of  aluminium  by  this  process,  I  have 
no  official  figures  to  present,  but  an  approximate  idea  can  easily 
be  estimated  from  the  data  given.  Pure  hydrated  alumina  should 
not  cost  over  3  cents  per  lb.,  and  since  it  contains  about  one-third 
water,  the  alumina  produced  costs  4  J  cents,  with  the  cost  of  cal- 
cination to  be  added,  which  should  not  be  over  1 J  cents  per  lb. 
The  bath  wastes  very  little,  let  us  suppose  15  per  cent,  of  the 
weight  of  aluminium  produced.  The  cost  of  power,  number  of 
men,  etc.,  will  have  to  be  guessed  at.  We  might  then  put  down 
for  twenty-four  hours7  work — 


100  Ibs.  calcined  alumina  (a)  6  cts. 
fluorides  for  bath  @  7  cts. 
carbons     .... 
50  horse-power  engine 
2  engineers  @  $3.00  per  diem    . 
6  workmen  (oj  $2.00        " 
Superintendence,  office  expenses,  etc. 
Interest  on  plant,  rent,  etc. 


Cost  of  about  50  Ibs.  of  aluminium       .         .         .        $50.00 

"When  the  large  plant  now  being  erected  is  in  operation,  the 
cost  of  aluminium  by  this  process  will  not  exceed  $0.50  per  lb. 

Cowles  Bros.'  Process. 

Messrs.  E.  H.  and  A.  H.  Cowles  patented  in  the  United  States 
and  Europe*  an  electric  furnace  and  its  application  for  producing 

*  U.  S.  Patents  324658,  324659,  Aug.  18,  1885  ;  English  Patent  9781,  same 
date  ;  German  Patent,  33672. 


294  ALUMINIUM. 

aluminium.  Their  patent  claims  "  reducing  an  aluminium  com- 
pound in  company  with  a  metal  in  presence  of  carbon  in  a  fur- 
nace heated  by  electricity;  the  alloy  of  aluminium  and  the  metal 
formed  being  further  treated  to  separate  out  the  aluminium." 
The  history  of  the  development  of  this  process  has  already  been 
sketched,  we  will  proceed  to  describe  the  details  of  its  operation. 
The  first  public  description  was  given  in  two  papers,  one  read 
before  the  American  Association  for  the  Advancement  of  Science* 
by  Prof.  Chas.  F.  Mabery,  of  the  Case  School  of  Applied  Science, 
Cleveland,  the  other  before  the  American  Institute  of  Mining 
Engineersf  by  Dr.  T.  Sterry  Hunt,  of  Montreal. 

Prof.  Mabery  said  in  his  paper  :  "  Some  time  since,  the  Messrs. 
Cowles  conceived  the  idea  of  obtaining  a  continuous  high  tem- 
perature on  an  extended  scale  by  introducing  into  the  path  of  an 
electric  current  some  material  that  would  afford  the  requisite 
resistance,  thereby  producing  a  corresponding  increase  in  the  tem- 
perature. After  numerous  experiments,  coarsely  pulverized  car- 
bon was  selected  as  the  best  means  for  maintaining  an  invariable 
resistance,  and  at  the  same  time  as  the  most  available  substance 
for  the  reduction  of  oxides.  When  this  material  mixed  with  the 
oxide  to  be  reduced  was  made  a  part  of  the  electric  circuit,  in- 
closed in  a  fire-clay  retort,  and  subjected  to  the  action  of  a  current 
from  a  powerful  dynamo,  not  only  was  the  oxide  reduced,  but  the 
temperature  increased  to  such  an  extent  that  the  whole  interior  of 
the  retort  fused  completely.  In  other  experiments  lumps  of  lime, 
sand,  and  corundum  were  fused,  with  a  reduction  of  the  corre- 
sponding metal ;  on  cooling,  the  lime  formed  large,  well-defined 
crystals,  the  corundum  beautiful  red -green  and  blue  octahedral 
crystals.  Following  up  these  results,  it  was  soon  found  that  tlie 
intense  heat  thus  produced  could  be  utilized  for  the  reduction  of 
oxides  in  large  quantities,  and  experiments  were  next  tried  on  a 
large  scale  with  the  current  from  a  fifty  horse-power  dynamo.  For 
the  protection  of  the  walls  of  the  furnace,  which  were  of  fire-brick, 
a  mixture  of  ore  and  coarsely  pulverized  gas-carbon  was  made  a  cen- 
tral core,  and  was  surrounded  on  the  side  and  bottom  by  fine  char- 

*  Ann  Arbor  Meeting,  Aug.  28,  1885. 
f  Halifax  Meeting,  Sept.  16,  1885. 


REDUCTION    BY   THE    USE   OF   ELECTRICITY.  295 

coal,  the  current  following  the  lesser  resistance  of  the  core  from 
carbon  electrodes  inserted  in  the  ends  of  the  furnace  in  contact 
with  the  core.  The  furnace  was  charged  by  first  filling  it  with 
charcoal,  making  a  trough  in  the  centre,  and  filling  this  with  the 
ore  mixture,  the  whole  being  covered  with  a  layer  of  coarse  char- 
coal. The  furnace  was  closed  on  top  with  fire-brick  slabs  con- 
taining two  or  three  holes  for  the  escape  of  the  gaseous  products 
of  the  reduction,  and  the  whole  furnace  was  made  air  tight  by 
luting  with  fire-clay.  Within  a  few  minutes  after  starting  the 
dynamo,  a  stream  of  carbonic  oxide  issued  through  the  openings, 
burning  usually  with  a  flame  eighteen  inches  high.  The  time 
required  for  complete  reduction  was  ordinarily  about  an  hour. 
Experience  has  already  shown  that  aluminium,  silicon,  boron, 
manganese,  sodium,  and  potassium  can  be  reduced  from  their 
oxides  with  ease.  In  fact,  there  is  no  oxide  that  can  withstand 
the  temperature  attainable  in  this  furnace.  Charcoal  is  changed 
to  graphite  ;  does  this  indicate  fusion  ?  As  to  what  can  be  accom- 
plished by  converting  enormous  electrical  energy  into  heat  within 
narrow  limits,  it  can  only  be  said  that  it  opens  the  way  into  an 
extensive  field  of  pure  and  applied  chemistry.  It  is  not  difficult 
to  conceive  of  temperature  limited  only  by  the  power  of  carbon 
to  resist  fusion. 

"  Since  the  motive  power  is  the  chief  expense  in  accomplishing 
reductions  by  this  method,  its  commercial  success  is  closely  con- 
nected with  obtaining  power  cheaply.  Realizing  the  importance 
of  this  point,  Messrs.  Cowles  have  purchased  at  Lockport,  N.  Y., 
a  water  power  where  they  can  utilize  1200  horse-power.  An 
important  feature  in  the  use  of  these  furnaces  from  a  commercial 
standpoint  is  the  slight  technical  skill  required  in  their  manipula- 
tion. The  four  furnaces  operated  in  the  experimental  laboratory 
at  Cleveland  are  in  charge  of  two  young  men,  who  six  months  ago 
knew  absolutely  nothing  of  electricity.  The  products  at  present 
manufactured  are  the  various  grades  of  aluminium  bronze,  made 
from  a  rich  furnace  product  obtained  by  adding  copper  to  the 
charge  of  ore.  Aluminium  silver  is  also  made  ;  and  a  boron 
bronze  may  be  prepared  by  the  reduction  of  boracic  acid  in  con- 
tact with  copper,  while  silicon  bronze  is  made  by  reducing  silica 
in  contact  with  copper.  As  commercial  results  may  be  mentioned 


296  ALUMINIUM. 

the  production  in  the  experimental  laboratory,  which  averages 
50  Ibs.  of  10  per  cent,  aluminium  bronze  daily,  which  can  be 
supplied  to  the  trade  in  large  quantities  on  the  basis  of  $5  per  Ib. 
for  the  aluminium  contained,  the  lowest  market  quotation  of  alu- 
minium being  now  $15  per  Ib." 

Dr.  Hunt  stated  further  that  if  the  mixture  consisted  of  alu- 
mina and  carbon  only,  the  reduced  metal  volatilized,  part  escaping 
into  the  air  and  burning  to  alumina,  part  condensing  in  the  upper 
layer  of  charcoal,  affording  thus  crystalline  masses  of  nearly  pure 
aluminium  and  yellow  crystals  supposed  to  be  a  compound  of 
aluminium  with  carbon.  Great  loss  was  met  in  collecting  this 
divided  metal  into  an  ingot,  so  that  only  small  quantities  were 
really  obtained.  To  gather  all  the  aluminium  together,  a  metal 
such  as  copper  was  added,  thus  producing  an  alloy  with  15  to  20 
per  cent,  of  aluminium  ;  on  substituting  this  alloy  for  pure  copper 
in  another  operation,  an  alloy  with  over  30  per  cent,  of  alumin- 
ium was  obtained. 

Dr.  Hunt,  in  a  later  paper,*  stated  that  pure  aluminium  has 
been  obtained  in  this  process  by  first  producing  in  the  furnace  an 
alloy  of  aluminium  and  tin,  then  melting  this  with  lead,  when  the 
latter  takes  up  the  tin  and  sinks  with  it  beneath  the  aluminium. 
He  also  stated  that  in  the  early  experiments  a  dynamo  driven  by  a 
30  horse-power  engine  yielded  a  daily  output  of  50  Ibs.  of  10  per 
cent,  aluminium  bronze,  but  with  a  larger  machine  the  output  was 
proportionately  much  greater.  In  the  latest  practice,  one-half 
cent  per  horse-power  per  hour  is  said  to  cover  the  expense  of 
working,  making  the  10  per  cent,  bronze  cost  about  5  cents  per 
Ib.  over  the  copper  used. 

Various  shapes  of  furnaces  have  been  used  by  the  Cowles  Bros., 
the  first  described  being  a  rectangular  box,  lined  with  carbon, 
with  the  electrodes  passing  through  the  ends.  Although  two 
other  forms  have  been  patented,  we  understand  that  the  kind  now 
used,  and  which  is  described  at  length  in  Mr.  Thompson's  paper, 
is  also  of  the  oblong,  horizontal  style.  Chas.  S.  Bradley  and 
Francis  B.  Crocker,  of  New  York,  patented  and  assigned  to  the 

*  National  Academy  of  Science,  Washington  Meeting,  April  30,  ]886. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  297 

Cowles  Electric  Smelting  Company,*  the  use  of  a  retort,  composed 
of  conducting  material,  surrounded  by  a  substance  which  is  a  poor 
conductor  of  heat,  and  having  inside  a  mixture  of  charcoal  and 
the  ore  to  be  heated.  Electric  connection  being  made  with  the 
ends  of  the  retort,  the  walls  of  the  retort  and  the  material  in  it 
are  included  in  the  circuit  and  constitute  the  greater  part  of  the 
resistance.  The  retort  may  be  stoppered  at  each  end  during  the 
operation,  and  the  heating  thus  performed  in  a  reducing  atmos- 
phere. Mr.  A.  H.  Cowles  devised  a  style  of  furnace  adapted  for 
continuous  working  and  utilizing  the  full  current  of  a  dynamo  of 
the  largest  size.f  The  electrodes  are  tube-shaped  and  placed 
vertically.  The  positive  pole  is  above,  and  is  surmounted  by 
a  funnel  in  which  the  mixture  for  reduction  is  placed.  The 
regular  delivery  of  the  mixture  is  facilitated  by  a  carbon  rod, 
passing  through  the  cover  of  the  funnel,  which  is  serrated  on  the 
end  and  can  be  worked  up  and  down.  The  melted  alloy  pro- 
duced, with  any  slag,  passes  down  through  the  negative  electrode. 
The  distance  between  the  poles  can  be  regulated  by  moving  the 
upper  one,  and  the  whole  is  inclosed  in  a  fire-brick  chamber. 
The  space  between  the  electrodes  and  the  walls  is  filled  with  an 
isolating  material,  which  is  compact  around  the  lower  electrode 
but  coarse  grained  around  the  upper  to  facilitate  the  escape  of  the 
gases  produced.  The  chamber  is  tightly  closed  excepting  a  small 
tube  for  the  escape  of  gas. 

A  very  complete  description  of  the  Cowles  process  was  given 
by  Mr.  W.  P.  Thompson  (agent  for  the  Cowles  Co.  in  England) 
in  a  paper  read  before  the  Liverpool  Section  of  the  Society  of 
Chemical  Industry. J  He  describes  the  process  as  then  carried  on 
in  Lockport;  the  dynamo  used  being  a  large  Brush  machine 
weighing  2J  tons  and  consuming  about  100  horse-power  in  being 
driven  at  900  revolutions  per  minute. 

"  Conduction  of  the  current  of  the  large  dynamo  to  the  furnace 
and  back  is  accomplished  by  a  complete  metallic  circuit,  except 
where  it  is  broken  by  the  interposition  of  the  carbon  electrodes 

*  U.  S.  Patent  335499,  Feb.  2,  1886. 

f  English  Patent  4664  (1887). 

t  Journal  of  the  Society  of  Chemical  Industry,  April  29,  1886. 


298  ALUMINIUM. 

and  the  mass  of  pulverized  carbon  in  which  the  reduction  takes 
place.  The  circuit  is  of  13  copper  wires,  each  0.3  inch  in  diame- 
ter. There  is  likewise  in  the  circuit  an  ampere  meter,  or  am- 
meter, through  whose  helix  the  whole  current  flows,  indicating 
the  total  strength  of  the  current  being  used.  This  is  an  impor- 
tant element  in  the  management  of  the  furnace,  for,  by  the  posi- 
tion of  the  finger  on  the  dial,  the  furnace  attendant  can  tell  to  a 
nicety  what  is  being  done  by  the  current  in  the  furnace.  Be- 
tween the  ammeter  and  the  furnace  is  a  resistance  coil  of  German 
silver  kept  in  water,  throwing  more  or  less  resistance  into  the 
circuit  as  desired.  This  is  a  safety  appliance  used  in  changing 
the  current  from  one  furnace  to  another,  or  to  choke  off  the  cur- 
rent before  breaking  it  by  a  switch. 

"  The  furnace  (see  Figs.  25,  26,  27)  is  simply  a  rectangular 
box,  A,  one  foot  wide,  five  feet  long  inside,  and  fifteen  inches 
deep,  made  of  firebrick.  From  the  opposite  ends  through  the 
pipes  BB  the  two  electrodes  (7(7  pass.  The  electrodes  are  im- 
mense electric-light  carbons  three  inches  in  diameter  and  thirty 
inches  long.  If  larger  electrodes  are  required,  a  series  this  size 
must  be  used  instead,  as  so  far  all  attempts  to  make  larger  car- 
bons that  will  not  disintegrate  on  becoming  incandescent  have 
failed.  The  ends  of  the  carbons  are  placed  within  a  few  inches 
of  each  other  in  the  middle  of  the  furnace,  and  the  resistance  coil 
and  ammeter  are  placed  in  the  circuit.  The  ammeter  registers 
50  to  2000  amperes.  These  connections  made,  the  furnace  is 
ready  for  charging. 

"  The  walls  of  the  furnace  must  first  be  protected,  or  the  in- 
tense heat  would  melt  the  fire  brick.  The  question  arose,  what 
would  be  the  best  substance  to  line  the  walls  ?  Finely  powdered 
charcoal  is  a  poor  conductor  of  electricity,  is  considered  infusible 
and  the  best  non-conductor  of  heat  of  all  solids.  From  these 
properties  it  would  seem  the  best  material.  As  long  as  air  is  ex-? 
eluded  it  will  not  burn.  But  it  is  found  that  after  using  pure 
charcoal  a  few  times  it  becomes  valueless ;  it  retains  its  woody 
structure,  as  is  shown  in  larger  pieces,  but  is  changed  to  graphite, 
a  good  conductor  of  electricity,  and  thereby  tends  to  diffuse  the 
current  through  the  lining,  heating  it  and  the  walls.  The  fine 
charcoal  is  therefore  washed  in  a  solution  of  lime-water,  and  after 


REDUCTION   BY   THE   USE   OF   ELECTRICITY. 


299 


drying,  each  particle  is  insulated  by  a  fine  coating  of  lime.  The 
bottom  of  the  furnace  is  now  filled  with  this  lining  about  two  or 
three  inches  deep.  A  sheet-iron  gauge  is  then  placed  along  the 
sides  of  the  electrodes,  leaving  about  two  inches  between  them. 


Fig.  25. 


Longitudinal  section.. 
Fig.  27. 


Transverse  section. 

and  the  side  walls,  in  which  space  more  of  the  charcoal  is  placed. 
The  charge  E,  consisting  of  about  25  pounds  of  alumina,  in  its 
native  form  as  corundum,  12  pounds  of  charcoal  and  carbon,  and 
50  pounds  of  granulated  copper,  is  now  placed  within  the  gauge 
and  spread  around  the  electrodes  to  within  a  foot  of  each  end  of 


300  ALUMINIUM. 

the  furnace.  For  making  iron  alloy,  where  silicon  also  is  not 
harmful,  beauxite  or  various  clays  containing  iron  and  silica  may 
be  used  instead  of  the  pure  alumina  or  corundum.  In  place  of 
granulated  copper,  a  series  of  short  copper  wires  or  bars  can  be 
placed  parallel  to  each  other  and  transverse  to  the  furnace,  among 
the  alumina  and  carbon,  it  being  found  that  where  grains  are 
used  they  sometimes  fuse  together  in  such  a  way  as  to  short-cir- 
cuit the  current.  After  this,  a  bed  of  charcoal,  F,  the  granules 
of  which  vary  in  size  from  a  chestnut  to  a  hickory,  is  spread  over 
all,  and  the  gauge  drawn  out.  This  coarse  bed  of  charcoal  above 
the  charge  allows  free  escape  of  the  carbonic  oxide  generated  in 
the  reduction.  The  charge  being  in  place,  an  iron  top,  6r,  lined 
with  fire  brick,  is  placed  over  the  whole  furnace  and  the  crevices 
luted  to  prevent  access  of  air.  The  brick  of  the  walls  insulate 
the  cover  from  the  current. 

"  Now  that  the  furnace  is  charged  and  the  cover  luted  down, 
it  is  started.  The  ends  of  the  electrodes  were  in  the  beginning 
placed  close  together,  as  shown  in  the  longitudinal  section,  and 
for  this  cause  the  internal  resistance  of  the  furnace  may  be  too 
low  for  the  dynamo,  and  cause  a  short  circuit.  The  operator, 
therefore,  puts  sufficient  resistance  into  the  circuit,  and  by  watch- 
ing the  ammeter  and  now  and  then  moving  one  of  the  electrodes 
out  a  trifle,  he  can  prevent  undue  short  circuiting  in  the  begin- 
ning of  the  operation.  In  about  ten  minutes,  the  copper  between 
the  electrodes  has  been  melted  and  the  latter  are  moved  far 
enough  apart  so  that  the  current  becomes  steady.  The  current  is 
now  increased  till  1300  amperes  are  going  through,  driven  by  50 
volts.  Carbonic  oxide  has  already  commenced  to  escape  through 
the  two  orifices  in  the  top,  where  it  burns  with  a  white  flame. 
By  slight  movements  outward  of  the  electrodes  during  the  com- 
ing five  hours,  the  internal  resistance  in  the  furnace  is  kept  con- 
stant, and  at  the  same  time  all  the  different  parts  of  the  charge 
are  brought  in  turn  into  the  zone  of  reduction.  At  the  close  of 
the  run  the  electrodes  are  in  the  position  shown  in  the  plan,  the 
furnace  is  shut  down  by  placing  a  resistance  in  the  circuit  and 
then  the  current  is  switched  into  another  furnace  charged  in  a 
similar  manner.  It  is  found  that  the  product  is  larger  if  the 
carbons  are  inclined  at  angles  of  30°  to  the  horizontal  plane. 


EEDUCTION   BY   THE   USE   OF    ELECTEICITY.  301 

"  This  regulating  of  the  furnace  by  hand  is  rather  costly  and 
unsatisfactory.  Several  experiments  have  therefore  been  tried 
to  make  it  self-regulating,  and  on  January  26,  1886,  a  British 
patent  was  applied  for  by  Cowles  Bros.,  covering  an  arrangement 
for  operating  the  electrodes  by  means  of  a  shunt  circuit,  electro- 
magnet, and  vibrating  armature.  Moreover,  if  the  electrodes 
were  drawn  back  and  exposed  to  the  air  in  their  highly  heated 
state,  they  would  be  rapidly  wasted  away.  To  obviate  this, 
Messrs.  Cowles  placed  what  may  be  called  a  stuffing-box  around 
them,  consisting  of  a  copper  box  filled  with  copper  shot.  The 
wires  are  attached  to  the  boxes  instead  of  the  electrodes.  The 
hot  electrodes  as  they  emerge  from  the  furnace  first  encounter 
the  shot,  which  rapidly  carry  off  the  heat,  and  by  the  time  they 
emerge  from  the  box  they  are  too  cool  to  be  oxidized  by  contact 
with  the  air. 

"  Ninety  horse-power  have  been  pumped  into  the  furnace  for 
five  hours.  At  the  beginning  of  the  operation  the  copper  first 
melted  in  the  centre  of  the  furnace.  There  was  no  escape  for  the 
heat  continually  generated,  and  the  temperature  increased  until 
the  refractory  corundum  melted,  and  being  surrounded  on  all 
sides  by  carbon  gave  up  its  oxygen.  This  oxygen,  uniting  with 
the  carbon  to  form  carbonic  oxide,  has  generated  heat  which  cer- 
tainly aids  in  the  process.  The  copper  has  had  nothing  to  do 
with  the  reaction,  as  it  will  take  place  in  its  absence.  Whether 
the  reaction  is  due  to  the  intense  heat  or  to  electric  action  it  is 
difficult  to  say.  If  it  be  electric,  it  is  Messrs.  Cowles7  impres- 
sion that  we  have  here  a  case  where  electrolysis  can  be  accom- 
plished by  an  alternating  current,  although  it  has  not  been  tried 
as  yet.  Were  the  copper  absent,  the  aluminium  set  free  would 
now  absorb  carbon  and  become  a  yellow,  crystalline  carbide  of 
aluminium ;  but,  instead  of  that,  the  copper  has  become  a  boiling, 
seething  mass,  and  the  bubblings  of  its  vapors  may  distinctly  be 
heard.  The  vapors  probably  rise  an  inch  or  two,  condense  and 
fall  back,  carrying  with  them  the  freed  aluminium.  This  con- 
tinues till  the  current  is  taken  off  the  furnace,  when  we  have  the 
copper  charged  with  15  to  30  per  cent.,  and  in  some  cases  as  high 
as  40  per  cent,  of  its  weight  of  aluminium,  and  a  little  silicon. 
After  cooling  the  furnace  this  rich  alloy  is  removed.  A  valuable 


302  ALUMINIUM. 

property  of  the  fine  charcoal  is  that  the  metal  does  not  spread 
and  run  through  its  interstices,  but  remains  as  a  liquid  mass  sur- 
rounded below  and  on  the  sides  by  fine  charcoal,  which  sustains 
it  just  as  flour  or  other  fine  dust  will  sustain  drops  of  water  for 
considerable  periods,  without  allowing  them  to  sink  in.  The 
alloy  is  white  and  brittle.  This  metal  is  then  melted  in  an  ordin- 
ary crucible  furnace,  poured  into  large  ingots,  the  amount  of 
aluminium  in  it  determined  by  analysis,  again  melted,  and  the 
requisite  amount  of  copper  added  to  make  the  bronze  desired. 

"  Two  runs  produce  in  ten  hours'  average  work  100  pounds  of 
white  metal,  from  which  it  is  estimated  that  Cowles  Bros.,  at 
Lockport,  are  producing  aluminium  in  its  alloys  at  a  cost  of  about 
40  cents  per  Ib.  The  Cowles  Company  will  shortly  have  1200 
horse-power  furnaces.  With  a  larger  furnace,  there  is  no  reason 
why  it  should  not  be  made  to  run  continuously  like  the  ordinary 
blast  furnace. 

"  In  place  of  the  copper  any  non- volatile  metal  may  be  used  as 
a  condenser  to  unite  with  any  metal  it  may  be  desired  to  reduce, 
provided,  of  course,  that  the  two  metals  are  of  such  a  nature  that 
they  will  unite  at  this  high  temperature.  In  this  way  aluminium 
may  be  alloyed  with  iron,  nickel,  silver,  tin,  or  cobalt.  Messrs. 
Cowles  have  made  alloys  containing  50  aluminium  to  50  of  iron, 
30  aluminium  to  70  of  copper,  and  25  aluminium  to  75  of  nickel. 
Silicon  or  boron  or  other  rare  metals  may  be  combined  in  the 
same  way,  or  tertiary  alloys  may  be  produced ;  as,  for  instance, 
where  fire-clay  is  reduced  in  presence  of  copper  we  obtain  an 
alloy  of  aluminium,  silicon,  and  .copper." 

Soon  after  Mr.  Thompson's  description,  the  plant  at  Lockport 
was  increased  by  the  addition  of  the  largest  dynamo  yet  con- 
structed, built  by  the  Brush  Electric  Company,  and  dubbed  the 
"Colossus."  This  machine  weighs  almost  ten  tons,  and  when 
driven  at  423  revolutions  per  minute,  with  68  volts  resistance  in 
the  external  circuit,  it  produced  a  useful  current  of  3400  amperes, 
or  at  405  revolutions  produced  a  current  of  3200  amperes  with 
83  volts  electro-motive  force,  indicating  249000  Watts  or  334 
electric  horse-power.  The  steam  engine  was,  in  the  latter  case, 
developing  nearly  400  horse-power,  and  could  not  supply  more; 
it  was  judged  that  the  dynamo  could  have  been  driven  to  300,000 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  303 

Watts  with  safety.  The  first  run  with  this  machine  was  made 
in  September,  1886.  The  furnaces  used  for  this  current  are  of 
the  same  style  as  that  described  by  Mr.  Thompson,  but  are  larger, 
the  charge  being  60  Ibs.  of  corundum,  60  Ibs.  of  granulated  copper, 
30  Ibs.  of  coarse  charcoal  besides  the  pulverized  lime-coated  char- 
coal used  in  packing.  The  operation  of  reducing  this  charge 
takes  about  two  hours.  As  soon  as  the  operation  is  finished  the 
current  is  switched  off  into  another  furnace  prepared  and  charged, 
so  that  the  dynamo  is  kept  working  continuously.  In  1888,  the 
Cowles  Company  had  two  of  these  large  dynamos  in  operation 
and  eight  furnaces  in  use.  With  two-hour  runs  a  furnace  is 
tapped  every  hour,  producing  about  80  Ibs.  of  bronze  averaging 
18  per  cent,  of  aluminium.  The  capacity  of  the  plant  is,  there- 
fore, about  1 J  tons  of  10  per  cent,  bronze  per  day.  Their  alloys 
are  now  sold  on  the  basis  of  $2.50  per  Ib.  for  the  contained 
aluminium. 

The  Cowles  Syndicate  Company,  of  England,  located  at  Stoke- 
on-Trent,  have  set  up  a  large  plant  at  Milton,  where,  profiting  by 
the  experience  of  the  parent  concern  in  America,  still  larger  elec- 
tric currents  are  used,  these  being  found  more  economical.  The 
dynamo  in  use  at  this  works  was  built  by  Crompton,  and  sup- 
plies a  current  of  5000-6000  amperes  at  50  to  60  volts.  There 
are  two  furnace-rooms,  each  containing  six  furnaces,  aluminium 
and  silicon  bronze  being  produced  in  one  room  and  ferro-alu- 
niinium  in  the  other.  The  furnaces  used  measure  60  by  20  by 
36  inches,  inside  dimensions.  The  electrodes  used  are  formed  by 
bundling  together  9  carbon  rods,  each  2  J  inches  in  diameter,  each 
electrode  weighing  20  Ibs.  More  recently  larger  carbons  have 
been  obtained,  3  inches  in  diameter,  and  an  electrode  formed  of 
five  of  these  weighs  36  Ibs.  The  furnace  is  charged  as  pre- 
viously described. 

The  current  is  started  at  3000  amperes,  gradually  increasing 
to  5000  during  the  first  half  hour,  and  then  keeping  steady  until 
the  run  is  ended,  which  is  about  one  and  a  half  hours  from  start- 
ing. The  product  of  each  run  is  about  100  Ibs.  of  raw  bronze 
containing  15  to  20  per  cent,  of  aluminium.  The  return  is  said 
to  average  1  Ib.  of  contained  aluminium  per  18  electric  horse- 
power per  hour,  or  1 J  Ibs.  per  electric  horse-power  per  day.  The 


304  ALUMINIUM. 

works  produce  about  200  Ibs.  of  aluminium  contained  in  alloys 
per  day.  The  raw  bronze  is  stacked  until  several  runs  have 
accumulated,  then  a  large  batch  is  melted  at  once  in  a  reverbera- 
tory  furnace,  refined,  and  diluted  to  the  proportion  of  aluminium 
required  by  adding  pure  copper. 

The  Cowles  Company,  both  in  England  and  America,  produce 
six  standard  grades  of  bronze  as  follows  : — 

"  Special"  A          .....     11  per  cent,  of  aluminium. 

A .     10 

B       .         .         .         .         ...       7 

C 

D      ...,,. 
E • 

Their  ferro-alu minium  is  sold  with  usually  5  to  7  per  cent,  of 
aluminium,  but  10, 13,  and  15  per  cent,  is  furnished  if  asked  for. 
Products  of  the  Cowles  furnace. — Dr.  W.  Hampe  obtained  the 
following  results  on  analyzing  a  sample  of  Cowles  Bros/  10  per 
cent,  bronze : — 

Copper  .         .         .         .         . 

Aluminium  .         .         .         .         . 
Silicon  .         .         .         .         . 

Carbon  .         .«..         .         . 

Magnesium    ..... 
Iron  ... 


100.013 

A  sample  of  10  per  cent,  bronze,  made  in  the  early  part  of 
1886,  and  analyzed  in  the  laboratory  of  the  Stevens  Institute, 
showed — 

Copper 88.0 

Aluminium  .........         6.3 

Silicon 6.5 

but  it  is  evident  that  the  percentage  of  silicon  has  since  then  been 
lowered. 

The  ferro-aluminium  used  by  Mr.  Keep  in  his  tests  on  cast- 
iron  was  furnished  by  the  Cowles  Company,  and  analyzed — 

Aluminium  .........       11.42 

Silicon  3.86 


REDUCTION   BY   THE  USE   OF   ELECTRICITY.  305 

A  sample  shipped  to  England  in  December,  1886,  contained — 

Iron 86.69 

Combined  carbon  ......  1.01 

Graphitic      " 1.91 

Total 2.92 

Silicon 2.40 

Manganese    .........  0.31 

Aluminium    .........  6.50 

Copper           .         ./      • 1.05 

Sulphur         .         .'.•'' 0.00 

Phosphorus  .      '  . 0.13 

100.00 

The  copper  in  this  alloy  was  present  by  accident,  the  alloy  regu- 
larly made  containing  none,  but  the  rest  of  the  analysis  gives 
a  correct  idea  of  the  constitution  of  the  alloy.  Prof.  Mabery 
gives  several  analyses  of  Cowles'  ferro-aluminium  : — * 

Iron 

Aluminium  . 
Silicon 
Carbon 

The  slags  formed  in  the  furnace  in  producing  this  alloy  were 
analyzed  as  follows  : — 

Silica .  .  0.78  4.10 

Alumina  (insoluble)      .         .         ,  .  .  0.20 

Lime 28.50  14.00 

Iron ;      .  .  .  1.50  29.16 

Alumina  (soluble)  +  aluminium  .  .  38.00  48.70 

Sulphur         .         .         .         ...  .  .  0.50 

Graphite        .         .         .                  .  .  .  5.00  2.60 

Combined  carbon       ••;..'.         .  ,  .  0.90  0.48 

The  slags  formed  when  producing  bronze  vary  in  composition, 
and  are  usually  crystalline,  with  a  shining,  vitreous  lustre.  Their 
analysis  shows — 

Alumina  (insoluble)     .      .  ,         .         .55.30  66.84 

Alumina  (soluble)  -f  aluminium          .    21.80  14.20 

Lime 3.70  1.44        6.77 

Copper         .;.  ' '•<  .        .        .  '      .         .       —  3.32        1.00 

Carbon  0.65 


85.17 

85.46 

86.04 

86.00 

84.00 

8.02 

8.65 

9.00 

9.25 

10.50 

2.36 

2.20 

2.52 

2.35 

2.40 

3.77 

2.41 

2.50 

*  American  Chemical  Journal,  1887,  p.  11. 
20 


26.70 

35.00 

20.00 

— 

66.20 

53.30 

74.32 

15.23 

5.00 

12.30 

2.86 

20.5& 

2.00 

0.20 

2.86 

— 

— 

— 

— 

49.26 

306  ALUMINIUM. 

The  lime  present  probably  existed  as  calcium  aluminate.  These 
slags  contained  only  a  small  amount  of  aluminium,  rarely  any 
iron,  and  were  usually  free  from  silica. 

The  same  chemist  analyzed  a  peculiar  product  sometimes 
formed  in  the  furnace  when  smelting  for  bronze,  in  the  shape  of 
crystalline  masses,  steel-gray  to  bright  yellow  in  color,  semi-trans- 
parent and  with  a  resinous  lustre.  These  all  contained  alu- 
minium, copper,  silicon  and  calcium  in  various  proportions,  and 
when  exposed  to  the  air  fell  to  powder.  Analyses  gave 

Copper 

Aluminium  .         .         , 
Silicon  .         ... 

Calcium         .         .         . 
Tin        .... 

99.90        100.80        100.04         85.04 

The  latter  product  was  formed  in  smelting  for  aluminium-tin. 

Prof.  Mabery  also  found  that  the  soot  collecting  at  the  orifices 
on  top  of  the  furnace  contained  10  to  12  per  cent,  of  aluminium ; 
also  that  when  alumina  and  carbon  alone  were  heated  and  silica 
was  present,  the  aluminium  formed  dissolved  up  to  10  per  cent, 
of  silicon,  which,  on  dissolving  the  aluminium  in  hydrochloric 
acid,  was  left  as  crystalline  or  graphitic  silicon. 

Reactions  in  Cowles''  process. — The  inventors,  themselves,  claim 
"  reduction  in  a  furnace  heated  by  electricity  in  presence  of  carbon 
and  a  metal."  In  their  first  pamphlet  they  say  that  "  the  Cowles 
process  accomplishes  the  reduction  of  alumina  by  carbon  and 
heat."  Professor  Mabery  and  Dr.  Hunt,  already  quoted,  and 
Dr.  Kosman*  look  at  the  process  in  no  other  light  than  that 
the  electric  current  is  utilized  simply  by  its  conversion  into  heat 
by  the  resistance  offered,  and  that  pure  electrolysis  is  either  absent 
or  occurs  to  so  small  an  extent  as  to  be  inappreciable.  Indeed, 
if  we  consider  the  arrangement  of  the  parts  in  the  Cowles  furnace 
we  see  every  effort  made  to  oppose  a  uniform,  high  resistance  to 
the  passage  of  the  current  and  so  convert  its  energy  into  heat, 
and  an  entire  absence  of  any  of  the  usual  arrangements  for 
electrolysis.  For  instance,  electroysis  requires  a  fluid  bath  in 

*  Stahl  und  Eisen,  Jan.  1889. 


REDUCTION   BY   THE   USE   OF    ELECTRICITY.  307 

circulation,  so  that  each  element  of  the  electrolyte  may  be  con- 
tinuously liberated  at  one  of  the  poles  and  the  presence  of  any 
foreign  material,  as  bits  of  carbon,  between  the  poles  is  to  be 
avoided  if  possible,  since  they  short-circuit  the  current  and  hinder 
electrolysis  proper.  I  think  the  arrangement  of  the  furnace 
shows  no  attempt  to  fulfil  any  of  the  usual  conditions  for  electrol- 
ysis, and  one  of  the  best  arrangements  for  converting  the  energy 
of  the  current  entirely  into  heat.  Dr.  Hampe,  however,  in  spite 
of  these  evident  facts,  draws  the  conclusion  that  because  he  was 
unable  to  reduce  alumina  by  carbon  in  presence  of  copper  at  the 
temperature  of  a  Deville  lime-furnace  that  it  was  therefore  to 
be  assumed  that  even  the  somewhat  higher  temperature  of  the 
electric  furnace  alone  would  be  insufficient  to  accomplish  the  de- 
sired reaction,  and  hence  the  effect  of  the  electric  arc  must  be  not 
only  electro-thermic  in  supplying  heat,  but  afterwards  electro- 
lytic, in  decomposing  the  fused  alumina. 

If  we  figure  out  the  useful  effect  of  the  current,  i.  e.,  the  pro- 
portion of  its  energy  utilized  for  the  purpose  of  reducing  alumina, 
we  find  a  low  figure,  but  it  is  well  to  note  that  although  the 
power  required  is  one  of  the  main  features  of  this  way  of  reduction 
yet  this  item  is  so  cheap  at  the  firm's  works  that  it  becomes  a 
secondary  consideration  in  the  economy  of  the  process.  A  300 
horse-power  current  is  equivalent  to  an  expenditure  of 

-  =  191000    calories    of   heat    per   hour.     Theo- 

191000 

retically,  this  amount  of  heat  would  produce =  26  J  kilos 

7.250 

or  58  pounds  of  aluminium.  However,  about  7  pounds  are  ob- 
tained in  an  hour's  working,  which  would  show  a  useful  effect  of 
12  per  cent.  This  should  even  be  diminished,  since  no  account 
has  been  taken  of  the  combustion  of  carbon  in  the  furnace  to  car- 
bonic oxide.  The  remainder  of  the  heat  account,  probably  90 
per  cent,  of  the  whole,  is  partly  accounted  for  by  the  heat  con- 
tained in  the  gases  escaping  and  the  materials  withdrawn  from 
the  furnace  (of  which  no  reasonable  estimate  can  be  made,  since 
the  question  of  temperatures  is  so  uncertain)  and  the  large  re- 
mainder must  be  put  down  as  lost  by  radiation  and  conduction. 
As  before  remarked,  water  power  is  obtained  by  this  company 


308  ALUMINIUM. 

very  cheaply,  and  even  this  large  loss  does  not  make  much  show 
in  the  cost  of  the  alloy,  yet  the  figures  show  that  a  much  larger 
useful  effect  should  be  possible,  and  it  is  not  at  all  improbable 
that  the  prospect  of  getting  double  or  triple  the  present  output 
from  the  same  plant  is  at  present  inciting  the  managers  to  fresh 
exertions  in  utilizing  the  power  to  better  advantage. 

Since  writing  the  above,  I  have  seen  Mr.  H.  T.  Dagger's  paper* 
on  the  Cowles  process  in  England,  in  which  the  product  at  their 
Milton  works  is  said  to  be  1  Ib.  of  aluminium  to  18  electric 
horse-power  per  hour,  which  would  show  that  the  dissociation  of 
the  alumina  represented  nearly  30  per  cent,  of  the  energy  of  the 
current,  but  the  data  given  in  the  body  of  this  gentleman's 
paper  (p.  303)  do  not  seem  to  indicate  so  large  a  return  as  is 
stated  above.  Mr.  Dagger,  moreover,  maintains  the  purely  elec- 
tro-thermic action  of  the  current,  denying  that  any  electrolysis 
takes  place  at  all. 

In  the  discussion  of  Heroult's  process  (p.  314)  it  will  be  shown 
that  in  both  it  and  Cowles'  process  the  largest  part  of  the  reduc- 
tion must  necessarily  be  performed  by  chemical  and  not  by  elec- 
trolytic action.  I  do  not  introduce  this  discussion  here,  since  the 
two  processes  resemble  each  other  so  closely  in  the  reaction  in- 
volved that  they  can  best  be  considered  together. 

Manges'  Patent. 

fThis  inventor  proposes  to  produce  aluminium  or  aluminium 
bronze  by  mixing  aluminous  material  with  suitable  conducting 
material,  such  as  coal,  and  a  cohesive  material,  then  pressing  into 
cylinders  and  baking  hard.  These  strong,  compact  bars  conduct 
electricity,  and  are  to  be  used  like  the  carbon  electrodes  of  electric 
lamps  in  a  suitably  inclosed  space. 

Farmer's  Patent. 

M.  G.  Farmer!  mixes  aluminous  material  with  molasses  or 
pitch,  making  a  paste  which  is  moulded  into  sticks,  burned,  and 

*  Read  before  the  British  Association  for  Adv.  Science,  Newcastle,  1889. 

f  German  Patent,  40354  (18S7). 

J  English  Patent,  10815,  Aug.  6,  1887. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  309 

used  as  electrodes,  inclosed  in  a  furnace.  Aluminium  is  produced 
by  the  arc,  and  drops  into  a  crucible  placed  immediately  beneath. 
It  appears  that  Messrs.  Menges  and  Farmer  hit  upon  the  same 
idea  at  about  the  same  time,  but  the  practicability  of  the  process 
as  outlined  has  still  to  be  demonstrated,  and  appears  to  be  very 
improbable  of  attainment. 

The  Heroult  Process  (1887). 

This  is  the  invention  of  P.  L.  C.  Heroult,  of  Paris,  and  has 
been  patented  in  the  United  States,  England,  and  most  European 
countries.*  As  has  already  been  outlined  in  Chapter  I.,  the 
process  was  first  put  in  operation  at  the  works  of  the  Societe 
Mettallurgique  Suisse,  at  Neuhausen  on  the  Rhine,  where  large 
water  power  is  obtained  from  the  Rhine-Falls. 

The  English  patent  is  headed  "an  improved  process  for  the 
production  of  aluminium,  aluminium  bronze,  and  other  alloys  of 
aluminium  by  electrolysis."  It  specifies  that  for  producing  pure 
aluminium  a  mixture  of  cryolite  and  alumina  is  fused  in  a  carbon 
crucible  contained  within  one  of  plumbago,  and  set  in  a  wind  fur- 
nace. The  inner  crucible  serves  as  the  cathode  of  an  electric 
current,  while  it  is  provided  with  a  lid  having  two  holes  through 
one  of  which  connection  is  made  by  a  carbon  rod  with  the  cruci- 
ble, through  the  other  another  carbon  rod  dips  into  the  middle 
of  the  bath.  The  cover  is  banked  up  with  loam  and  garden 
mould ;  the  two  carbon  rods  being  protected  from  oxidation  by 
passing  through  earthen  tubes  which  pass  through  the  arch  of  the 
furnace  above.  By  using  a  current  of  3  volts  electro-motive  force 
the  alumina  is  electrolyzed,  aluminium  being  deposited  on  the 
walls  of  the  crucible  and  a  corresponding  amount  of  oxygen  set 
free  at  the  carbon  anode,  which  is  gradually  consumed,  thereby 
producing  carbonic  oxide.  The  bath  must  be  replenished  with 
alumina  and  the  anode  renewed  from  time  to  time.  To  form 
alloys,  as  of  copper,  the  metal  is  melted  in  a  carbon  crucible  by 
a  voltaic  arc,  the  positive  pole  being  a  movable  carbon  rod  above 

*  U.  S.  Patent,  387876,  August  14,  1888  ;    English  Patent,  7426,  June  21, 
1887  ;  French  Patent,  170003,  April  15,  1887. 


310  ALUMINIUM. 

and  the  copper  serving  as  the  negative  pole,  connection  being 
made  with  the  crucible.  When  the  copper  is  melted,  alumina  is 
introduced  by  degrees,  without  any  flux.  The  intense  heat  fuses 
the  alumina,  and  it  is  electrolyzed  between  the  copper  and  the 
carbon  anode  above.  The  electrolyte  is  then  liquid  alumina,  and 
it,  as  well  as  the  copper  cathode,  is  kept  melted  solely  by  the  heat 
developed  by  the  electric  current.  The  alloy  is  tapped  out  and 
fresh  materials  added  at  suitable  intervals  without  interruption  to 
the  process.  A  convenient  strength  of  current  for  a  crucible  20 
centimetres  deep  by  14  centimetres  in  diameter  inside,  with  a 
carbon  anode  5  centimetres  in  diameter,  is  found  to  be  400  am- 
peres, with  an  electro-motive  force  of  20  to  25  volts.  An  ampere- 
meter introduced  into  the  circuit  indicates  the  progress  of  the 
operation  and  the  necessity  for  tapping  or  adding  new  material. 

Of  the  two  processes  described  in  the  above  specification  the 
first  is  very  similar  to  that  of  Henderson,  and  to  Hall's  process 
(pp.  273  and  288),  and  has  not  been  exploited  as  the  second  one 
has  been.  For  some  time  the  province  of  the  "  Heroult  process" 
has  generally  been  considered  to  be  in  producing  aluminium  alloys, 
which  is  the  second  part  of  the  English  patent  and  the  whole  sub- 
ject of  the  United  States  patent  referred  to.  We  must  therefore 
conclude  that  the  process  for  producing  pure  aluminium  has  been 
abandoned,  and  our  subsequent  remarks  will  be  concerned  solely 
with  the  process  for  producing  the  alloys. 

The  Societe  Metallurgique  Suisse,  which  owned  the  patents, 
put  up  a  plant  on  a  commercial  scale  in  July,  1888.  It  is  said 
that  this  firm  experimented  some  time  with  Dr.  Kleiner's  process, 
but  abandoned  it,  about  the  middle  of  1887,  to  try  Heroult's  pro- 
cess, and  with  such  successful  results  that  the  plant  about  to  be 
described  was  decided  on.  The  instalment  consisted  of  two  large 
dynamos  constructed  especially  for  this  work  by  the  Oerliken 
Engineering  Company,  and  directly  coupled  to  a  300  horse-power 
Jonval  turbine  situated  between  them  and  mounted  on  a  horizon- 
tal shaft.  A  separate  dynamo  of  300  amperes  and  65  volts, 
driven  by  a  belt  from  a  pullej7  upon  the  main  shaft,  is  used  to 
excite  the  field  magnets  of  the  two  large  machines.  These  large 
dynamos  were  originally  intended  to  give  each  a  current  of  6000 
amperes  at  20  volts  electro-motive  force  when  running  at  180 


REDUCTION    BY   THE   USE   OF   ELECTRICITY.  311 

revolutions  per  minute,  but  sufficient  margin  was  allowed  in  the 
strength  of  the  field  to  be  able  to  work  to  30  volts.  They  have 
even  worked  up  to  35  volts  on  unusual  occasions  without  any 
undue  heating.  It  happens  sometimes  that  the  end  of  the  anode 
touches  the  molten  cathode,  producing  a  short  circuit,  when  the 
current  will  suddenly  rise  to  from  20,000  to  25,000  amperes 
without,  however,  damaging  the  machine. 

The  main  conductors  are  naked  copper  cables,  about  10  cen- 
timetres diameter,  and  no  special  precautions  are  taken  to  insulate 
them,  since  the  current  is  of  comparatively  low  potential,  and  a 
leakage  of  100  amperes  more  or  less  in  such  a  large  current  is  too 
insignificant  to  take  the  trouble  to  avoid.  An  amperemeter  is 
placed  in  the  main  circuit,  its  dial  being  traversed  by  an  index 
about  1  metre  long,  which  is  closely  watched  by  the  workman 
controlling  the  furnace. 

The  furnace  or  crucible  first  used  consisted  of  an  iron  box  cast 
around  a  carbon  block,  the  iron,  on  contracting  by  cooling,  securely 
gripping  the  surface  of  the  carbon  on  all  sides,  and  thus  insuring 
perfect  contact  and  conduction  of  the  current  from  the  cathode 
inside.  This  method  was  found  only  suitable  for  small  crucibles, 
and  the  next  furnace  was  built  up  of  carbon  slabs  held  together 
by  a  strong  wrought-iron  casing.  The  interior  depth  of  the 
crucible  was  60  centimetres,  length  50  and  breadth  35  centimetres, 
which  would  permit  the  introduction  of  the  carbon  anode  and 
leave  a  clear  space  of  4  centimetres  all  around  it  horizontally. 
At  the  botton  of  the  cavity  is  a  passage  to  a  tap-hole,  D  (Fig.  28), 
closed  by  the  plug  E,  which  is  withdrawn  from  time  to  time  to 
run  off  the  alloy.  The  carbon  anode,  F,  is  suspended  vertically 
above  the  crucible  by  pulleys  and  chains,  which  permit  it  to  be 
raised  and  lowered  easily  and  quickly.  This  anode  is  built  up  of 
large  carbon  slabs  laid  so  as  to  break  joints,  and  securely  fastened 
together  by  carbon  pins.  The  whole  bar  is  250  centimetres  long 
with  a  section  of  43  by  25  centimetres,  and  weighs  complete  255 
kilos.  The  conductor  is  clamped  to  the  anode  by  means  of  the 
copper  plates,  G.  The  crucible  is  covered  on  top  by  carbon 
slabs,  Hj  Hj  5  centimetres  thick,  leaving  an  opening  just  large 
enough  for  the  anode  to  pass  through.  The  openings,  J,  J,  closed 
by  the  lids,  K,  K,  serve  for  introducing  fresh  copper  and  alumina. 


312 


ALUMINIUM. 


The  materials  used  have  just  been  mentioned.  Electrolytic  or 
Lake  Superior  copper  is  used,  the  former  being  perhaps  preferred 
if  from  a  good  manufacturer.  The  alumina  is  bought  as  commer- 
cial hydrated  alumina,  costing  in  Europe  22  francs  per  100  kilos 


(2  cents  per  lb.).  This  is,  of  course,  calcined  before  using,  each 
100  kilos  furnishing  about  65  kilos  of  alumina.  Corundum  can 
be  substituted  for  the  artificial  alumina ;  some  from  North  Caro- 
lina was  tried,  and  is  said  to  have  given  even  more  satisfactory 
results.  Commercial  beauxite  has  been  used,  but  since  it  con- 
tains more  or  less  iron  its  use  is  confined  to  the  manufacture  of 
ferro-aluminium.  It  is  very  cheap  in  Europe,  and  requires  no 
other  preparation  than  simple  calcining. 

The  operation  is  begun  by  placing  copper,  broken  into  rather 
small  pieces,  in  the  crucible.  The  carbon  anode  is  then  approached 
to  the  copper,  which  is  quickly  melted  by  the  current.  The  bath 
of  fluid  copper  then  becomes  the  negative  pole,  and  ore  is  imme- 
diately fed  into  the  crucible.  It  also  is  soon  melted  and  floats  on 
top  of  the  copper.  The  electrolysis  now  proceeds,  care  being 
taken  that  while  the  anode  dips  into  the  molten  ore,  it  does  not 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  313 

touch  the  molten  cathode.  Particular  stress  is  laid  on  the  econ- 
omy of  keeping  the  distance  between  the  electrodes  small,  the 
reason  given  being  that  "  the  space  between,  being  filled  with  a 
layer  of  badly-conducting  molten  ore,  offers  a  resistance  which 
increases  with  the  distance ;  and  although  resistance  is  necessary, 
in  order  that  the  current  should  produce  heat,  it  is  not  economical 
to  have  more  heat  than  is  necessary  to  melt  the  ore — the  work  of 
separating  the  metal  from  the  oxygen  being. chiefly  done  by  the 
electrolytic  action  of  the  current,  and  not  by  the  high  temperature." 
In  practice,  this  intervening  space  is  not  over  3  millimetres  (one- 
tenth  of  an  inch).  The  workman  in  charge,  by  watching  the 
indications  of  the  amperemeter,  is  enabled  to  maintain  the  anode 
at  its  proper  distance  without  any  difficulty ;  it  is  proposed  to  do 
this  regulating  automatically  by  means  of  an  easily-constructed 
electrical  device.  The  oxygen  liberated  gradually  burns  away 
the  anode,  it  being  found  that  about  1  kilo  of  the  anode  is  con- 
sumed for  every  kilo  of  aluminium  produced. 

After  the  operation  commences,  the  alumina  and  metal  are 
introduced  alternately  in  small  quantities  at  frequent  and  regular 
intervals,  and  the  alloy  is  tapped  out  about  every  twelve  hours. 
The  only  wear  to  which  the  crucible  is  subjected  is  from  the 
accidental  admission  of  small  quantities  of  air ;  this  waste  is 
scarcely  appreciable.  All  oxygen  evolved  from  the  bath  is 
evolved  in  contact  with  the  anode  and  burns  it.  When  the  anode 
has  worn  down  until  too  short  for  further  use,  it  is  replaced  by 
another,  the  pieces  of  carbon  left  being  utilized  for  repairing, 
covering  or  building  up  the  crucible.  The  operation  is  kept  up 
night  and  day,  and  it  is  generally  more  than  a  day  after  start- 
ing before  the  crucible  is  thoroughly  up  to  its  maximum  heat 
and  work.  Two  reliefs  of  five  men  each  operate  the  plant,  one 
to  superintend,  one  to  prepare  and  dry  the  alumina,  a  third  to 
control  the  working  of  the  crucible  by  working  the  anode,  a 
fourth  to  feed  ore  and  metal  into  the  crucible,  and  the  fifth  to 
take  care  of  the  machinery,  prepare  anodes,  crucibles,  etc.  All 
five  work  together  to  replace  an  anode  or  tap  the  crucible.  A 
part  of  each  tapping  is  analyzed,  to  determine  its  percentage  of 
aluminium.  It  is  the  aim  to  produce  as  rich  a  bronze  as  possible 
at  the  first  operation  (over  42  per  cent,  of  aluminium  has  been 


314  ALUMINIUM. 

reached)  and  its  subsequent  dilution  to  any  percentage  desired  is 
done  in  any  ordinary  smelting  furnace. 

The  average  current  supplied  the  crucible  is  8000  amperes  and 
28  volts,  requiring  an  expenditure  of  a  little  over  300  horse- 
power in  the  turbine.  Starting  cold  it  required,  in  one  instance, 
36  hours  to  produce  670  kilos  of  aluminium  bronze  containing 
18.3  per  cent,  or  122.67  kilos  of  aluminium.  Taking  the  cur- 
rent as  300  electric  horse-power,  this  would  be  a  return  of  11 
grammes  per  hour  or  0.264  kilos  (0.6  Ibs.)  per  day  for  each 
electric  horse-power.  It  is  claimed  by  Mr.  Heroult  that  the 
furnace  takes  several  days  to  attain  its  full  efficiency,  and  that 
when  it  does  so  the  above  charge  can  be  worked  in  12  hours, 
which  would  triple  the  above  production  per  horse-power.  This 
claim  is  backed  by  figures  as  to  271  hours  of  actual  operation, 
during  which  time  the  crucible  cooled  several  times,  but  the 
average  over  the  whole  period  was  22|  grammes  per  hour  or 
0.544  kilos  (1.2  Ibs.)  per  day  for  each  horse-power  (163  kilos  of 
aluminium  per  day,  total  production).  During  actual  operation 
at  full  efficiency,  Mr.  Heroult  claims  to  get  35  to  40  grammes  of 
aluminium  per  horse-power-hour,  which  would  mean  11  to  15 
horse-power-honrs  per  pound  of  aluminium,  or  1.75  to  2.1  Ibs.  of 
aluminium  per  horse-power  per  day. 

An  idea  of  the  percentage  of  useful  effect  derived  from  the  cur- 
rent may  be  had  very  easily  by  considering  that  1  electric  horse- 
power =  750  Watts  =  644.4  calories  of  heat  per  hour.  (See 
p.  247.)  As  each  gramme  of  aluminium  evolves  7.25  calories 
in  forming  alumina,  the  production  of  1  electric  horse-power  in 
1  hour  (if  its  energy  were  utilized  solely  for  separating  aluminium 
from  oxygen)  would  be  88.88  grammes.  Therefore  the  heat 
energy  of  the  current  is  amply  sufficient  to  account  for  all  the 
alumina  decomposed,  leaving  over  the  heat  produced  in  the 
crucible  by  the  union  of  oxygen  with  the  carbon  anode.  Looking 
at  the  other  side  of  the  question,  the  electrolytic  action,  we  can 
easily  calculate  from  the  strength  of  the  current  what  it  could  per- 
form. A  current  of  8000  amperes  can  liberate  2.68  kilos  of  alu- 
minium per  hour,*  according  to  the  fundamental  law  of  electro- 

*  N.  B.     Only  one  furnace  is  used  on  the  circuit. 


REDUCTION   BY   THE   USE   OF   ELECTRICITY.  315 

deposition.  If,  then,  from  the  figures  given,  there  was  actually 
produced  3.3  kilos  and  6.8  kilos  per  hour,  and  10.5  to  12  kilos 
are  claimed  when  up  to  full  efficiency,  it  is  impossible  that  more 
than  a  fraction  of  the  aluminium  is  produced  by  electrolytic  decom- 
position of  alumina,  and  the  claim  that  the  process  is  essentially 
electrolytic  is  without  foundation.  Similar  calculations  with  the 
data  given  with  regard  to  Cowles'  process  will  lead  to  exactly 
similar  conclusions,  viz  :  that  the  absolute  energy  of  the  current, 
if  converted  into  its  heat  equivalent,  is  many  times  more  than 
sufficient  to  account  for  the  decomposition  of  the  alumina  on 
thermal  grounds,  but  the  amount  of  current  used  will  not  suffice 
to  explain  the  decomposition  of  the  alumina  as  being  electrolytic. 
Therefore,  in  both  these  processes  the  oxygen  is  abstracted  from 
alumina  by  carbon,  the  condition  allowing  this  to  take  place  being 
primarily  the  extremely  high  temperature  and  secondarily  the 
fluidity  of  the  alumina.  The  presence  of  copper  is  immaterial, 
as  is  clearly  shown  in  the  Cowles  process. 

The  Heroult  process  has  been  rapidly  extended.  In  November, 
1888,  a  syndicate  was  formed  in  Berlin,  with  a  capital  of  $2,500,- 
000,  which  purchased  the  Heroult  continental  patents  and  has 
united  with  the  former  Swiss  owners  in  forming  the  Aluminium 
Industrie  Actien  Gesellschaft,  which  has  commenced  to  erect  a 
very  large  plant  in  place  of  the  former  one,  at  Neuhausen.  Dr. 
Kiliani  has  been  made  manager  of  the  works,  which  are  being 
rapidly  completed,  and  will  include,  when  finished,  foundries  and 
machine  shops  for  casting  and  utilizing  their  product.  The  new 
plant  will  consist  of  8  crucibles,  capable  of  producing  at  least  10 
tons  of  ten  per  cent,  bronze  in  24  hours. 

In  the  beginning  of  1889,  the  Societe  Electro-Metallurgique  of 
France,  located  at  Froges  (Isere),  commenced  to  manufacture 
alloys  by  the  Heroult  process.  Their  plant  consists  of  two  tur- 
bines of  300  horse-power  each,  with  two  dynamos  of  7000 
amperes  and  20  volts  each.  The  output  is  estimated  at  3000 
kilos  of  alloys  per  day,  which  probably  means  200  to  300  kilos 
of  aluminium. 

An  experimental  plant,  under  the  direction  of  Mr.  Heroult, 
was  started  in  July,  1889,  at  Bridgeport,  Conn.,  but  the  dynamo 


316  ALUMINIUM. 

proved  inadequate  to  the  work  required  and  was  burnt  out,  stop- 
ping operations  temporarily.  A  dynamo  was  then  ordered  from 
the  Oerliken  Works,  at  Zurich,  which  arrived  the  following 
November,  and  another  plant  has  been  started  at  Boonton,  N.  J. 
The  American  company  has  not  yet  been  incorporated. 


CHAPTER  XII. 

REDUCTION  OF  ALUMINIUM  COMPOUNDS  BY  OTHER  MEANS  THAN 
SODIUM  OR  ELECTRICITY. 

No  very  exact  classification  of  these  numerous  propositions  can 
be  made,  since  often  many  reducing  agents  are  claimed  in  one 
general  process.  Where  such  general  statements  are  made,  the 
method  will  be  found  under  the  most  prominent  reducing  agent 
named,  with  cross  references  under  the  other  headings. 

REDUCTION  BY  CARBON  WITHOUT  THE  PRESENCE  OF  OTHER 

METALS. 

About  the  first  attempt  of  this  nature  we  can  find  record  of,  is 
the  following  article  by  M.  Chapelle  : — * 

"  When  I  heard  of  the  experiments  of  Deville,  I  desired  to 
repeat  them,  but  having  neither  aluminium  chloride  nor  sodium 
to  use,  I  operated  as  follows :  I  put  natural  clay,  pulverized  and 
mixed  with  ground  sodium  chloride  and  charcoal,  into  an  ordinary 
earthen  crucible  and  heated  it  in  a  reverberatory  furnace,  with 
coke  for  fuel.  I  was  not  able  to  get  a  white  heat.  After  cooling, 
the  crucible  was  broken,  and  gave  a  dry  pulverulent  scoria  in 
which  were  disseminated  a  considerable  quantity  of  small  globules 
about  one-half  a  millimetre  in  diameter,  and  as  white  as  silver. 
They  were  malleable,  insoluble  in  nitric  or  cold  hydrochloric 
acids,  but  at  60°  dissolved  rapidly  in  the  latter  with  evolution 

*  Compt.  Rendus,  1854,  vol.  xxxviii.  p.  358. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  317 

of  hydrogen ;  the  solution  was  colorless  and  gave  with  ammonia 
a  gelatinous  precipitate  of  hydrated  alumina.  My  numerous 
occupations  did  not  permit  me  to  assure  myself  of  the  purity  of 
the  metal.  Moreover,  the  experiment  was  made  under  conditions 
which  leave  much  to  be  desired,  but  my  intention  is  to  continue 
my  experiments  and  especially  to  operate  at  a  higher  temperature. 
In  addressing  this  note  to  the  Academy  I  but  desire  to  call  the 
attention  of  chemists  to  a  process  which  is  very  simple  and  sus- 
ceptible of  being  improved.  I  hope  before  many  days  to  be  able 
to  exhibit  larger  globules  than  those  which  my  first  experiment 
furnished." 

M.  Chapelle  never  did  address  any  further  communications  to 
the  Academy  on  this  subject,  and  we  must  presume  that  further 
experiments  did  not  confirm  these  first  ones.  The  author  was 
once  called  upon  to  examine  a  slag  full  of  small,  white,  metallic 
globules,  the  result  of  fusing  slate-dust  in  a  similar  manner  to 
M.  Chapelle's  treatment  of  clay.  They  proved  to  be  globules  of 
siliceous  iron  reduced  from  the  iron  oxide  present  in  the  slate.  It 
is  not  impossible  that  Chapelle's  metallic  globules  were  something 
similar  in  composition  to  these. 

G.  W.  Reinar*  states  that  the  pyrophorous  mass,  which  results 
from  igniting  potash  or  soda  alum  with  carbon,  contains  a  car- 
boniferous alloy  of  aluminium  with  potassium  or  sodium,  from 
which  the  alkaline  metal  can  be  removed  by  weak  nitric  acid. 

The  manager  of  an  aluminium  company  in  Kentucky  claims 
to  produce  pure  aluminium  by  a  process  which  the  newspapers 
state  consists  in  smelting  down  clay  and  cryolite  in  a  water- 
jacketed  cupola  reducing  furnace,  it  being  also  stated  that  the 
aluminium  is  reduced  so  freely,  and  gathers  under  the  slag  so 
well,  that  it  is  tapped  from  the  furnace  by  means  of  an  ordinary 
syphon-tap.  These  are  all  the  particulars  which  have  been  made 
public.  As  to  whether  this  company  really  does  make  alumin- 
ium by  any  such  process,  I  am  unable  to  assert ;  about  all  that 
can  be  said  further  is  that  it  has  advertised  its  metal  extensively 
at  $2  to  $3  per  lb.,  and  a  sample  of  it  sent  to  a  friend  of  mine 
upon  application  was  truly  aluminium  of  fair  quality. 

*  Wagner's  Jahresb.,  1859,  p.  4. 


318  ALUMINIUM. 

O.  M.  Thowless,*  of  Newark,  N.  J.,  proposes  to  prepare  a  solu- 
tion, of  aluminium  chloride  by  dissolving  precipitated  aluminium 
hydrate  in  hydrochloric  acid.  The  solution  is  concentrated  and 
mixed  with  chalk,  coal,  soda,  and  cryolite,  and  the  mass  resulting 
heated  in  closed  vessels  to  a  strong,  red  heat.  It  is  also  stated 
that  aluminium  fluoride  may  be  used  instead  of  the  chloride. 
The  resulting  fused  mass  is  powdered  and  washed,  when  it  is  said 
that  aluminium  is  obtained  in  the  residue. 

According  to  a  patent  granted  to  Messrs.  Pearson,  Liddon,  and 
Pratt,  of  Birmingham,  f  an  intimate  mixture  is  made  by  grinding 
together — 

100  parts  cryolite. 

50     "      beauxite,  kaolin  or  aluminium  hydrate. 
50     "      calcium  chloride,  oxide  or  carbonate. 
50     "      coke  or  anthracite. 

These  are  heated  to  incipient  fusion  in  a  carbon-lined  furnace  or 
crucible  for  two  hours,  when  the  aluminium  is  said  to  be  pro- 
duced and  to  exist  finely  disseminated  through  the  mass.  A  mix- 
ture of  25  parts  each  of  potassium  and  sodium  chlorides  is  then 
to  be  added  and  the  heat  raised  to  bright  redness,  when  the  alu- 
minium collects  in  the  bottom  of  the  crucible.  A  better  utiliza- 
tion of  the  fine  powder  is  effected  by  washing  it,  drying,  and 
then  pouring  fused  zinc  upon  it,  which  alloys  with  the  aluminium 
and  can  be  afterwards  removed  by  distillation.  If  melted  copper 
is  used,  a  bronze  is  obtained. 

REDUCTION  BY  CARBON  AND  CARBON  DIOXIDE. 

J.  Morris,J  of  Uddington,  claims  to  obtain  aluminium  by  treat- 
ing an  intimate  mixture  of  alumina  and  charcoal  with  carbon  di- 
oxide. For  this  purpose,  a  solution  of  aluminium  chloride  is  mixed 
with  powdered  wood-charcoal  or  lampblack,  then  evaporated  till 
it  forms  a  viscous  mass  which  is  shaped  into  balls.  During  the 
evaporation  hydrochloric  acid  is  given  off.  The  residue  consists 

*  U.  S.  Patent,  370220,  Sept.  20,  1887 ;  English  Patent,  14407  (1886). 

f  English  Patent,  5316,  April  10,  1888. 

t  Dingier,  1883,  vol.  259,  p.  86.     German  Pat.,  No.  22150,  Aug.  30,  1882. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  319 

of  alumina  intimately  mixed  with  carbon.  The  balls  are  dried, 
then  treated  with  steam  in  appropriate  vessels  for  the  purpose  of 
driving  off  all  the  chlorine,  care  being  taken  to  keep  the  tempera- 
ture so  high  that'  the  steam  is  not  condensed.  The  temperature 
is  then  raised  so  that  the  tubes  are  at  a  low  red  heat,  and  dry 
carbon  dioxide,  CO2,  is  then  passed  through.  This  gas  is  reduced 
by  the  carbon  to  carbonic  oxide,  CO,  which  now,  as  affirmed  by 
Mr.  Morris,  reduces  the  alumina.  Although  the  quantity  of 
carbonic  oxide  escaping  is  in  general  a  good  indication  of  the  pro- 
gress of  the  reduction,  it  is,  nevertheless,  not  advisable  to  continue 
heating  the  tubes  or  vessels  until  the  evolution  of  this  gas  has 
ceased,  as  in  consequence  of  slight  differences  in  the  consistency 
of  the  balls  some  of  them  give  up  all  their  carbon  sooner  than 
others.  The  treatment  with  carbon  dioxide  lasts  about  thirty 
hours  when  the  substances  are  mixed  in  the  proportion  of  five 
parts  carbon  to  four  parts  alumina.  Morris  states  further  that 
the  metal  appears  as  a  porous  spongy  mass,  and  is  freed  from  the 
residual  alumina  and  particles  of  charcoal  either  by  smelting  it, 
technically  u  burning  it  out/'  with  cryolite  as  a  flux  or  by  mechani- 
cal treatment. 

KEDUCTION  BY  HYDROGEN. 

F.  W.  Gerhard*  decomposes  aluminium  fluoride  or  cryolite  by 
subjecting  them  to  hydrogen  at  a  red  heat.  The  aluminium  com- 
pound is  placed  in  a  number  of  shallow  dishes  of  glazed  earthen- 
ware, each  of  which  is  surrounded  by  a  number  of  other  dishes 
containing  iron  filings.  These  dishes  are  placed  in  an  oven  pre- 
viously heated  to  redness,  hydrogen  gas  is  then  admitted,  and  the 
heat  increased.  Aluminium  then  separates,  hydrofluoric  acid, 
HF,  being  formed,  but  immediately  taken  up  by  the  iron  filings 
and  thereby  prevented  from  reacting  on  the  aluminium.  To 
prevent  the  pressure  of  the  gas  from  becoming  too  great,  an  exit 
tube  is  provided,  which  may  be  opened  or  closed  at  pleasure.  This 
process,  patented  in  England  in  1856,  No.  2920,  is  ingenious  and 

*  Watts'  Dictionary,  article  "Aluminium." 


320  ALUMINIUM. 

was  said  to  yield  good  results.     The  inventor  has,  however,  re- 
turned to  the  use  of  the  more  costly  reducing  agent,  sodium, 
which  would  seem  to  imply  that  the  hydrogen  method  has  not  yet 
quite  fulfilled  his  expectations. 
(See  also  Comenge's  processes.) 

.REDUCTION  BY  CARBURETTED  HYDROGEN. 

Mr.  A.  L.  Fleury,*  of  Boston,  mixes  pure  alumina  with  gas- 
tar,  resin,  petroleum,  or  some  such  substance,  making  it  into  a 
stiff  paste  which  may  be  divided  into  pellets  and  dried  in  an 
oven.  They  are  then  placed  in  a  strong  retort  or  tube  which  is 
lined  with  a  coating  of  plumbago.  In  this  they  are  exposed  to 
a  cherry-red  heat.  The  retort  must  be  sufficiently  strong  to  stand 
a  pressure  of  from  25  to  30  Ibs.  per  square  inch,  and  be  so 
arranged  that  by  means  of  a  safety  valve  the  necessary  amount 
of  some  hydrocarbon  may  be  introduced  into  the  retort  among 
the  heated  mixture,  and  a  pressure  of  20  to  30  Ibs.  must  be  main- 
tained. The  gas  is  forced  in  by  a  force  pump.  By  this  process 
the  alumina  is  reduced,  the  metal  remaining  as  a  spongy  mass 
mixed  with  carbon.  This  mixture  is  remelted  with  metallic  zinc, 
and  when  the  latter  has  collected  the  aluminium  it  is  driven  off 
by  heat.  The  hydrocarbon  gas  under  pressure  is  the  reducing 
agent.  The  time  required  for  reducing  100  Ibs.  of  alumina,  earth, 
cryolite,  or  other  compound  of  aluminium,  should  not  be  more 
than  four  hours.  When  the  gas  can  be  applied  in  a  previously 
heated  condition  as  well  as  being  strongly  compressed,  the  reduc- 
tion takes  place  in  a  still  shorter  period. 

Nothing  is  now  heard  of  this  process,  and  it  has  been  presum- 
ably a  failure.  It  is  said  that  several  thousand  dollars  were 
expended  by  Mr.  Fleury  and  his  associates  without  making  a 
practical  success  of  it.  We  should  be  glad  to  hear  in  the  future 
that  their  sacrifices  have  not  been  in  vain,  and  that  the  process 
still  has  possibilities  in  it  which  will  some  time  be  realized. 

Petitjeanf  states  that  aluminium  sulphide,  or  the  double  sul- 

*  Chemical  News,  June,  1869,  p.  332. 

f  Polytechnisches  Central  Blatt.,  1858,  p.  888. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  321 

phide  of  aluminium  and  sodium  (see  p.  144),  may  be  reduced  by 
putting  them  into  a  crucible  or  retort,  through  the  bottom  of 
which  is  passed  a  stream  of  carburetted  hydrogen.  Some  solid 
or  liquid  hydrocarbon  may  be  placed  in  the  bottom  of  the  cru- 
cible. The  aluminium  is  said  to  be  thus  separated  from  its  com- 
bination with  sulphur.  The  powder  must  be  mixed  with  metallic 
filings,  as  iron,  and  melted,  in  order  to  collect  the  aluminium. 
Or,  metallic  vapor  may  be  passed  into  the  retort  in  place  of 
carburetted  hydrogen. 

Messrs.  Reillon,  Montague,  and  Bourgerel*  patent  the  pro- 
duction of  aluminium  sulphide  (see  p.  143)  and  its  reduction  by 
carburetted  hydrogen  exactly  as  above. 

REDUCTION  BY  CYANOGEN. 

According  to  Knowles'  patent,t  aluminium  chloride  is  reduced 
by  means  of  potassium  or  sodium  cyanide,  the  former,  either 
fused  or  in  the  form  of  vapor,  being  brought  in  contact  with 
either  the  melted  cyanide  or  its  vapor.  The  patent  further  states 
that  pure  alumina  may  be  added  to  increase  the  product.  The 
proportions  necessary  are  in  general — 

3  equivalents  of  aluminium  chloride. 
3-9  "  potassium  or  sodium  cyanide. 

4-9  "  alumina. 

Corbelli,  of  Florence,!  patented  the  following  method  in  Eng- 
land :  Common  clay  is  freed  from  all  foreign  particles  by  wash- 
ing, then  well  dried.  One  hundred  grammes  of  it  are  mixed 
with  six  times  its  weight  of  concentrated  sulphuric  or  hydro- 
chloric acid ;  then  the  mixture  is  put  in  a  crucible  and  heated  to 
400°  or  500°.  The  mass  resulting  is  mixed  with  200  grammes  of 
dry  yellow  prussiate  of  potash  and  150  grammes  of  common 
salt,  and  this  mixture  heated  in  a  crucible  to  whiteness.  After 
cooling,  the  reduced  aluminium  is  found  in  the  bottom  of  the 
crucible  as  a  button. 


*  English  Patent  4576,  March  28,  1887. 
f  Sir  Francis  C.  Knowles,  English  Patent,  1857,  No.  1742. 
J  English  Patent,  1858,  No.  142. 
21 


322  ALUMINIUM. 

According  to  Deville's  experiments,  this  process  will  not  give 
any  results.  Watts  remarks  that  any  metal  thus  obtained  must 
be  very  impure,  consisting  chiefly  of  iron. 

Lowthian  Bell*  attempted  to  obtain  aluminium  in  his  labora- 
tory by  exposing  to  a  high  heat  in  a  graphite  crucible  mixtures  of 
alumina  and  potassium  cyanide,  with  and  without  carbon.  In 
no  case  was  there  a  trace  of  the  metal  discovered. 

REDUCTION  BY  DOUBLE  REACTION. 

M.  Comenge,f  of  Paris,  produces  aluminium  sulphide  (see  p. 
143)  and  reduces  it  by  heating  it  with  alumina  or  aluminium 
sulphate  in  such  proportions  that  sulphurous  acid  gas  and  alu- 
minium may  be  the  sole  products.  The  mixture  is  heated  to 
redness  on  the  bed  of  a  reverberatory  furnace,  in  an  unoxidizing 
atmosphere,  the  reaction  being  furthered  by  agitation.  It  is 
stated  that  the  resulting  mass  may  be  treated  in  the  way  com- 
monly used  in  puddling  spongy  iron  and  afterwards  pressed  or 
rolled  together.  The  reactions  involved  would  be,  if  they  oc- 
curred, 

A12S3+  2A1203=  6A1  +  3S02. 
A12S3  +  A12(S04)3-  4A1  +  6S02. 

It  is  also  claimed  that  metallic  alloys  may  be  prepared  by  the 
action  of  metallic  sulphides  on  aluminium  sulphate  ;  as,  for  in- 
stance — 

A12(SO4)3  +  3FeS=  Al2Fe3  +  6SO2. 

The  sulphide  is  also  reduced  by  hydrogen,  iron,  copper  or  zinc, 
the  reactions  being 


APS3 

In  the  case  of  reduction  by  a  metal,  alloys  are  formed. 

Mr.  Niewerth'sJ  process  may  be  operated  in  his  newly  invented 
furnace,  but  it  may  also  be  carried  on  in  a  crucible  or  other  form 

*  Chemical  Reactions  in  Iron  Smelting,  p.  230. 

f  English  Patent,  1858,  No.  461,  under  name  of  J.  H.  Johnson. 

J  Sci.  Am.  Snppl.,  Nov.  17,  1885. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  323 

of  furnace.  The  furnace  alluded  to  consists  of  three  shaft  fur- 
naces, the  outer  ones  well  closed  on  top  by  iron  covers,  and  con- 
nected beneath  by  tubes  with  the  bottom  of  the  middle  one:  the 
tubes  being  provided  with  closing  valves.  These  side  shafts  are 
simply  water-gas  furnaces,  delivering  hot  water-gas  to  the  central 
shaft,  and  by  working  the  two  alternately  supplying  it  with  a 
continuous  blast.  The  two  producers  are  first  blown  very  hot  by 
running  a  blast  of  air  through  them  with  their  tops  open,  then 
the  cover  of  one  is  closed,  the  blast  shut  off,,  steam  turned  on  just 
under  the  cover,  and  water-gas  immediately  passes  from  the  tube 
at  the  bottom  of  the  furnace  into  the  central  shaft.  The  middle 
shaft  has  meanwhile  been  filled  with  these  three  mixtures  in  their 
proper  order : — 

First.  A  mixture  of  sodium  carbonate,  carbon,  sulphur  and 
alumina. 

Second.  Aluminium  sulphate. 

Third.  A  flux,  preferably  a  mixture  of  sodium  and  potassium 
chlorides. 

This  central  shaft  must  be  already  strongly  heated  to  commence 
the  operation,  it  is  best  to  fill  it  with  coke  before  charging,  and  as 
soon  as  that  is  hot  to  put  the  charges  in  on  the  coke.  Coke  may 
also  be  mixed  with  the  charges,  but  it  is  not  necessary.  The 
process  then  continues  as  follows- :  The  water-gas  enters  the  bottom 
of  the  shaft  at  a  very  high  temperature.  These  highly  heated 
gases,  carbonic  oxide  and  hydrogen,  act  upon  the  charges  so  that 
the  first  breaks  up  into  a  combination  of  sodium  sulphide  and 
aluminium  sulphide,  from  which,  by  double  reaction  with  the 
second  charge  of  aluminium  sulphate,  free  aluminium  is  produced. 
As  the  latter  passes  down  the  shaft,  it  is  melted  and  the  flux 
assists  in  collecting  it,  but  is  not  absolutely  necessary.  Instead 
of  producing  this  double  sulphide,  pure  aluminium  sulphide 
might  be  used  for  the  first  charge,  or  a  mixture  which  would  gen- 
erate it ;  or  again  pure  sulphide  of  sodium,  potassium,  copper,  or 
any  other  metallic  sulphide  which  will  produce  the  effect  alone,  in 
which  case  aluminium  is  obtained  alloyed  with  the  metal  of  the 
sulphide.  Instead  of  the  first  charge,  a  mixture  of  alumina,  sul- 
phur and  carbon  might  be  introduced.  Or  the  aluminium  sul- 
phate of  the  second  charge  might  be  replaced  by  alumina.  So 


324  ALUMINIUM. 

one  charge  may  be  sulphide  of  sodium,  potassium  or  any  other 
metallic  sulphide,  and  the  second  charge  may  be  either  alumina 
or  aluminium  sulphate. 

Messrs.  Pearson,  Turner,  and  Andrews*  claim  to  produce  alu- 
minium by  heating  silicate  of  alumina  or  compound  silicates  of 
alumina  and  other  bases  with  calcium  fluoride  and  sodium  or 
potassium  carbonate  or  hydrate,  or  all  of  these  together.  If  other 
metals  are  added,  alloys  are  obtained. 

REDUCTION  IN  PRESENCE  OF  on  BY  COPPER. 

Calvert  and  Johnson f  obtained  copper  alloyed  with  aluminium 
by  recourse  to  a  similar  chemical  reaction  to  that  employed  to 
get  their  iron-aluminium  alloy.  Their  mixture  was  composed 
of— 

20  equivalents  of  copper      .,.,'«.        ,         *         .      640  parts. 
8  (24)     "  aluminium  chloride     .        .        .    1076      " 

10  "  lime    .         .        V        .        .     '    ;      280      " 

"We  mixed  these  substances  intimately  together,  and  after 
having  subjected  them  to  a  high  heat  for  one  hour  we  found  at 
the  bottom  of  the  crucible  a  melted  mass  covered  with  cuprous 
chloride,  Cu2CP,  and  in  this  mass  small  globules,  which  on 
analysis  contained  8.47  per  cent,  aluminium,  corresponding  to  the 
formula — 

5  equivalents  of  copper  .         .         .      160  91.96  per  cent. 

1  "  aluminium    .         .        14  8.04 

100.00 

"  We  made  another  mixture  of  aluminium  chloride  and  copper 
in  the  same  proportions  as  above,  but  left  out  the  lime.  We  ob- 
tained an  alloy  in  this  case  also,  which  contained  12.82  per  cent, 
aluminium,  corresponding  to  the  formula — 

3  equivalents  of  copper  ...        96  87.27  per  cent. 

1  "  aluminium    .         .        14  12.73 

100.00 


*  English  Patent,  12332,  Sept.  12,  1887. 
f  Phil.  Mag.  1855,  x.  242. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  325 

M.  Evrard,*  in  order  to  make  aluminium  bronze,  makes  use 
of  an  aluminous  pig-iron.  (It  is  not  stated  how  this  aluminous 
pig-iron  is  made.)  This  is  slowly  heated  to  fusion,  and  copper  is 
added  to  the  melted  mass.  Aluminium,  having  more  affinity  for 
copper  than  for  iron,  abandons  the  latter  and  combines  with  the 
copper.  After  the  entire  mass  has  been  well  stirred,  it  is  allowed 
to  cool  slowly  so  as  to  permit  the  bronze,  which  is  heavier  than 
iron,  to  find  its  way  to  the  bottom  of  the  crucible.  M.  Evrard 
makes  silicon  bronze  in  the  same  way  by  using  siliceous  iron. 

Benzonf  has  patented  the  reduction  of  aluminium  with  copper, 
forming  an  aluminium-copper  alloy.  He  mixes  copper,  or  oxi- 
dized copper,  or  cupric  oxide,  in  the  finest  possible  state,  with 
fine,  powdered,  pure  alumina  and  charcoal,  preferably  animal  char- 
coal. The  alumina  and  copper  or  copper  oxide  are  mixed  in 
equivalent  proportions,  but  an  excess  of  charcoal  is  used.  The 
mixture  is  put  in  a  crucible  such  as  is  used  for  melting  cast-steel, 
which  is  lined  inside  with  charcoal.  The  charge  is  covered  with 
charcoal,  and  the  crucible  subjected  first  to  a  temperature  near 
the  melting  point  of  copper,  until  the  alumina  is  reduced,  and 
then  the  heat  is  raised  high  enough  to  melt  down  the  alloy.  In 
this  way  can  be  obtained  a  succession  of  alloys,  whose  hardness 
and  other  qualities  depend  on  the  percentage  of  aluminium  in  them. 
In  order  to  obtain  alloys  of  a  certain  composition,  it  is  best  to 
produce  first  an  alloy  of  the  highest  attainable  content  of  alu- 
minium, to  analyze  it,  and  then  melt  it  with  the  required  quantity 
of  copper.  The  same  process  can  be  used  for  the  reduction  of 
alumina  with  iron  or  ferric  oxide,  only  the  carbon  must  in  this  case 
be  in  greater  excess,  and  a  stronger  heat  kept  up  longer  must  be 
used  than  when  producing  the  copper-aluminium  alloy.  In  con- 
tact with  ferric  oxide  the  alumina  is  more  easily  reduced  than 
with  metallic  iron. 

Benzon  further  remarks  that  some  of  these  alloys,  as  the  ferro- 
aluminium,  may  be  subsequently  treated  so  as  to  separate  out  the 
metallic  aluminium ;  also  that  the  iron  alloy  may  be  mixed  with 
steel  in  the  melting  pot,  or  suitable  proportions  of  alumina  and 
carbon  may  be  put  into  the  melting  pot.  The  iron  alloy  may  be 

*  Annales  du  Genie  Civil,  Mars,  1867,  p.  189. 
t  Eng.  Pat.  1858,  No.  2753. 


326  ALUMINIUM. 

useful  for  many  purposes,  especially  in  the  manufacture  of  cast- 
steel. 

The  question  opened  up  by  Benzon's  statements  is  whether  car- 
bon reduces  alumina  in  presence  of  copper.  This  has  been  the 
subject  of  many  careful  experiments,  and  the  verdict  of  the  most 
reliable  observers  is  that  at  ordinary  furnace  temperatures  it  does 
not.  This  principle  has  been  the  subject  of  numerous  patents, 
and  before  presenting  the  negative  evidence  on  this  point  we  will 
review  the  claims  made  in  these  patents. 

G.  A.  Faurie*  states  that  he  has  succeeded  in  obtaining  alu- 
minium bronze  by  taking  two  parts  of  pure,  finely-powdered  alu- 
mina, making  it  into  a  paste  with  one  part  of  petroleum  and  then 
adding  one  part  of  sulphuric  acid.  When  the  yellow  color  is  uni- 
form and  the  mass  homogeneous,  sulphur  dioxide  begins  to  escape. 
The  paste  is  then  wrapped  up  in  paper  and  thrown  into  a  crucible 
heated  to  full  redness,  where  the  petroleum  is  decomposed.  The 
calcined  product  is  cooled,  powdered  and  mixed  with  an  equal 
weight  of  a  metal  in  powder,  e.  g.,  copper.  This  mixture  is  put 
into  a  graphite  crucible  and  heated  to  whiteness  in  a  furnace  sup- 
plied with  blast.  Amidst  the  black,  metallic  powder  are  found 
buttons  of  aluminium  alloy.  In  an  English  patent,  f  by  Mr. 
Faurie,  it  is  further  claimed  that  by  making  bricks  out  of  the 
calcined  alumina  mixture  and  alloying  metal,  and  using  similar 
bricks  of  lixiviated  soda  ashes  mixed  with  tar  for  flux,  the  re- 
duction can  be  affected  in  a  cupola. 

Bolley,J  at  his  laboratory  in  Zurich,  and  List,§  at  the  royal 
foundry  at  Augsburg,  have  shown  that  by  following  the  process 
claimed  by  Benzon  the  resulting  copper  contained  either  no  alu- 
minium, or  at  most  a  trace.  In  an  experiment  made  by  the 
author  to  test  this  point — 

40  grammes  of  copper  oxide  and  copper, 
5         "  alumina, 

5         "  charcoal, 

*  Comptes  Rendue,  105,  494,  Sept.  19,  1887. 

t  English  Patent,  10043,  Aug.  18,  1887. 

J  Schweizer  Polytechnisches  Zeitschrift,  1860,  p.  16. 

§  Wagner's  Jahresbericht,  1865,  p.  23. 


KEDUCTION   BY   MISCELLANEOUS   AGENTS.  327 

were  intimately  mixed  and  finely  powdered,  put  in  a  white-clay 
crucible  and  covered  with  cryolite.  The  whole  was  slowly  heated 
to  bright  redness,  and  kept  there  for  two  hours.  A  bright  button 
was  found  at  the  bottom  of  the  crucible.  This  button  was  of  the 
same  specific  gravity  as  pure  copper,  and  a  qualitative  test  showed 
no  trace  of  aluminium  in  it.  A  friend  of  mine,  Dr.  Lisle,  has 
repeated  this  experiment,  taking  the  metal  produced  and  return- 
ing it  to  another  operation  and  repeating  this  four  times,  but  the 
resulting  button  scarcely  showed  a  trace  of  aluminium. 

Dr.  W.  Hampe  has  lately  made  an  exhaustive  test  of  this  sub- 
ject with  the  following  conclusions  : — * 

"  The  reduction  of  alumina  by  carbon,  although  often  patented, 
is  on  thermo-chemical  grounds  highly  improbable,  but  since  alu- 
minium in  alloying  with  copper,  especially  in  the  proportions 
9.7  parts  of  the  former  to  90.3  parts  of  the  latter  (AlCu4),  evolves 
much  heat,  it  might  be  possible  that  the  reaction 

APO3  +  3C  -f  8Cu  =  2  AlCu4  -f  SCO 

is  exothermic.  I  therefore  mixed  alumina  with  the  necessary 
quantity  of  lamp-black  and  copper,  in  other  cases  evaporated 
together  to  dryness  solutions  of  aluminium  and  copper  nitrates, 
afterwards  igniting  them  to  oxides  and  adding  the  necessary 
amount  of  carbon.  These  mixtures  were  put  into  gas-carbon 
crucibles  contained  within  plumbago  pots  with  well-luted  covers, 
and  heated  in  a  Deville  blast-furnace  to  a  temperature  sufficient 
to  frit  together  the  quartz  sand  with  which  the  space  between  the 
two  crucibles  had  been  filled.  In  no  case  was  there  a  trace  of 
aluminium  produced,  nor  did  the  addition  of  any  flux  for  the 
alumina  affect  the  result  in  any  way." 

The  possibility  of  reducing  aluminium  sulphide  by  copper  has 
been  generally  decided  affirmatively.  M.  Comenge  claimed  that 
it  was  possible  (see  p.  322),  Reichelf  also  stated  unreservedly  that 
copper  filings  performed  the  reduction  at  a  high  temperature.  In 
an  experiment  by  the  author,  copper  foil  was  used  instead  of 
copper  filings,  the  latter  not  being  immediately  at  hand,  and  the 

*  Chemiker  Zeitung  (Cothen),  xii.  p.  391  (1888). 
f  Journal  fiir  Pr.  Chemie,  xi.  p.  55. 


328  ALUMINIUM. 

result  was  negative.  As  a  similar  test  with  iron  filings  gave  a 
good  result,  it  seems  quite  probable  that  copper  would  have 
performed  the  reduction  under  proper  conditions. 

Andrew  Mann,*  of  Twickenham,  patents  a  process  which  may 
be  stated  briefly  as  follows  :  Aluminium  sulphate  is  mixed  with 
sodium  chloride  and  heated  until  a  reaction  begins  to  take  place. 
The  mass  is  mixed  intimately  with  lime,  and  to  this  mixture  alu- 
minium sulphate  and  ground  coke  added.  This  is  calcined,  the 
powder  mixed  with  a  metal,  as  copper,  and  melted  down.  In 
this  case  the  slags  are  calcium  sulphide  and  copper  chloride,  while 
aluminium  bronze  is  obtained. 

L.  Q.  Brin,f  of  Paris,  claims  to  produce  aluminium  bronze  by 
the  following  process  :  Sheet  copper  is  cleaned  by  pickling,  and 
then  covered  with  a  mixture  of  2  parts  borax,  2  parts  common 
salt,  and  1  part  sodium  carbonate,  made  into  a  paste  with  water. 
The  metal  is  then  put  into  a  reverberatory  furnace,  heated  to 
bright  redness  and  vapors  of  aluminium  chloride  led  over  it,  car- 
ried in  by  a  current  of  inert  gas.  (It  is  stated  that  the  vapors 
of  aluminium  chloride  are  produced  by  heating  in  a  retort  a  mix- 
ture of  clay,  salt,  and  fluorspar.)  The  aluminium  compound  is 
said  to  be  decomposed,  and  the  nascent  aluminium  to  combine 
with  the  copper  forming  1J  to  2  per  cent,  bronze  at  one  opera- 
tion, and  by  using  this  over  it  may  be  enriched  to  any  extent 
desired.  In  a  modification  of  this  method,  the  coating  put  on 
the  metal  contains  clay  or  other  earth  rich  in  alumina.  It  is 
also  stated  that  the  metal  thus  coated  can  be  put  into  a  cupola 
with  alternate  layers  of  fuel  and  run  down  to  an  alloy. 

REDUCTION  BY  OR  IN  PRESENCE  OF  IRON. 

M.  Comenge  claims  that  aluminium  sulphide  is  reduced  by 
iron  (see  p.  322) ;  the  statement  is  repeated  by  a  writer  in  the 
"  Chemical  News,"  1860 ;  F.  LauterbornJ  states  that  the  reduc- 
tion takes  place  at  a  red  heat ;  Reichel§  also  records  his  success 

*  English  Patent,  9313,  June  30,  1887 ;  German  Patent,  45755,  Dec.  20, 
1887. 

f  English  Patents,  3547-8-9,  March  7,  1888  ;  U.  S.  Patent,  410574,  Sept.  10, 
1889. 

J  Dingier,  242,  70.  §  Jrul.  fiir  Pr.  Chemie,  xi.  55. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  329 

in  this  reaction  ;  finally,  the  author  has  obtained  encouraging 
results.  I  used  a  product  containing  32.3  per  cent,  of  aluminium 
sulphide.  On  mixing  this  intimately  with  fine  iron  filings,  and 
subjecting  to  a  high  heat  for  one  and  a  half  hours,  the  product 
was  a  loose  powder  in  which  were  small  buttons  of  metal.  They 
were  bright,  yellower  than  iron,  and  contained  by  analysis  9.66 
per  cent,  of  aluminium. 

H.  Xiewerth*  has  patented  the  following  process :  "  Ferro- 
silicum  is  mixed  with  aluminium  fluoride  in  proper  proportions 
and  the  mixture  submitted  to  a  suitable  red  or  melting  heat  by 
which  the  charge  is  decomposed  into  volatile  silicon  fluoride 
(SiF4),  iron  and  aluminium,  the  two  latter  forming  an  alloy.  In 
order  to  obtain  the  valuable  alloy  of  aluminium  and  copper  from 
this  iron-aluminium  alloy,  the  latter  is  melted  with  metallic  cop- 
per, which  will  then  by  reason  of  greater  affinity  unite  with  the 
aluminium,  while  the  iron  will  retain  but  an  insignificant  amount 
of  it.  On  cooling  the  bath,  the  bronze  and  iron  separate  in  such 
a  manner  that  they  can  readily  be  kept  apart.  In  place  of  pure 
aluminium  fluoride,  cryolite  may  advantageously  be  employed, 
or  aluminium  chloride  may  also  be  used,  in  which  case  silicon 
chloride  volatilizes  instead  of  the  fluoride.  Or,  again,  pure  silicon 
may  be  used  with  aluminium  fluoride,  cryolite,  or  aluminium 
chloride,  in  which  case  pure  aluminium  is  obtained." 

Mr.  W.  P.  Thompsonf  has  taken  out  a  patent  in  England^  for 
the  manufacture  of  aluminium  and  similar  metals,  which  is  car- 
ried out  as  follows  :  The  inventor  employs  as  a  reducing  agent 
iron,  either  alone  or  conjointly  with  carbon  or  hydrogen.  The 
operation  is  effected  in  an  apparatus  similar  to  a  Bessemer  con- 
verter, divided  into  two  compartments.  In  one  of  these  com- 
partments is  placed  melted  iron,  or  an  alloy  of  iron,  which  is 
made  to  run  into  the  second  by  turning  the  converter.  This  last 
compartment  has  two  tuyeres,  one  of  which  serves  to  introduce 
hydrogen,  while  by  the  other  is  introduced  either  aluminium 
chloride,  fluoride,  double  chloride  or  double  fluoride  with  sodium, 
in  liquid  or  gaseous  state.  In  presence  of  the  hydrogen,  the  iron 

*  Sci.  Am.  Suppl.,  Nov.  17,  1883. 

f  Bull,  de  la  Soc.  Chem.  de  Paris,  1880,  xxiv.  719. 

J  March  27,  1879,  No.  2101. 


330  ALUMINIUM. 

takes  up  chlorine  or  fluorine,  chloride  or  fluoride  of  iron  is  dis- 
engaged, and  aluminium  mixed  with  carbon  remains  as  a  residue. 
Then  this  mixture  of  iron,  aluminium  and  carbon  is  returned  to 
the  other  compartment  where  the  carbon  is  burnt  out  by  means 
of  a  current  of  air.  The  mass  being  then  returned  to  the  cham- 
ber of  reduction,  the  operation  described  is  repeated.  When 
almost  all  the  iron  has  been  consumed,  the  reduction  is  termi- 
nated by  hydrogen  alone.  There  is  thus  obtained  an  alloy  of 
iron  and  aluminium.  (The  preparation  of  sodium  does  not  re- 
quire the  intervention  of  hydrogen.  A  mixture  of  iron  with  an 
excess  of  carbon  and  caustic  soda  (NaOH)  is  heated  in  the  con- 
verter, when  the  sodium  distils  off.  When  all  the  carbon  has 
been  burnt,  the  iron  remaining  as  a  residue  may  be  converted  into 
Bessemer  steel.  As  iron  forms  an  alloy  with  potassium,  the 
method  would  scarcely  serve  for  the  production  of  that  metal.) 
To  obtain  the  pure  aluminium,  sodium  is  first  prepared  by  the 
process  indicated,  the  chloride  or  fluoride  of  aluminium  is  intro- 
duced into  the  apparatus  in  the  other  chamber,  when  the  metal 
is  reduced  by  the  vapor  of  sodium.  The  chambers  ought  to  be 
slightly  inclined,  and  an  agitator  favors  the  reaction.  The 
inventor  intends  to  apply  his  process  to  the  manufacture  of  mag- 
nesium, strontium,  calcium  and  barium. 

Calvert  and  Johnson*  made  experiments  on  the  reduction  of 
aluminium  by  iron,  and  the  production  thereby  of  iron-aluminium 
alloys.  We  give  the  report  in  their  own  words : — 

"  We  shall  not  describe  all  the  fruitless  efforts  we  made,  but 
confine  ourselves  only  to  those  which  gave  satisfactory  results. 
The  first  alloy  we  obtained  was  by  heating  to  a  white  heat  for 
two  hours  the  following  mixture  : — 

8  equivalents  of  aluminium  chloride     .         .         .     1076  parts. 
40             "              iron  filings            ....     1120      " 
8  "  lime 224      " 

"  The  lime  was  added  to  the  mixture  with  the  view  of  remov- 
ing the  chlorine  from  the  aluminium  chloride,  so  as  to  liberate 
the  metal  and  form  fusible  calcium  chloride,  CaCl2.  Subtracting 
the  lime  from  the  above  proportion,  we  ought  to  have  obtained  an 

*  Phil.  Mag.,  1855,  x.  240. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  331 

alloy  having  the  composition  of  1  equivalent  of  aluminium  to 
5  equivalents  of  iron,  or  with  9.09  per  cent,  of  aluminium.  The 
alloy  we  obtained  contained  12  per  cent.,  which  leads  to  the  for- 
mula AlFe4.  This  alloy,  it  will  be  noticed,  has  an  analogous 
composition  to  the  one  we  made  of  iron  and  potassium,  and  like 
it  was  extremely  hard,  and  rusted  when  exposed  to  a  damp  atmos- 
phere. Still  it  could  be  forged  and  welded.  We  obtained  a 
similar  alloy  by  adding  to  the  above  mixture  some  very  finely 
pulverized  charcoal  and  subjecting  it  to  a  high  heat  in  a  forge 
furnace  for  two  hours.  This  alloy  gave  on  analysis  12.09  per 
cent.*  But,  in  the  mass  of  calcium  chloride  and  carbon  remain- 
ing in  the  crucible  there  was  a  large  amount  of  globules  varying 
in  size  from  a  pin-head  to  a  pea,  as  white  as  silver  and  extremely 
hard,  which  did  not  rust  in  the  air  or  in  hyponitric  fumes.  Its 
analysis  gave  24.55  per  cent,  aluminium ;  the  formula  APFe3 
would  give  25  per  cent.  Therefore  this  alloy  has  an  analogous 
composition  to  alumina,  iron  replacing  oxygen.  We  treated  these 
globules  with  Aveak  sulphuric  acid,  which  removed  the  iron  and 
left  the  aluminium,  the  globules  retaining  their  form,  and  the 
metal  thus  obtained  had  all  the  properties  of  the  pure  aluminium. 
"  We  have  made  trials  with  the  following  mixture,  but  although 
they  have  yielded  results,  still  they  are  not  sufficiently  satisfactory 
to  describe  in  this  paper,  which  is  the  first  of  a  series  we  intend 
publishing  on  alloys.  This  mixture  was  : — 

Kaolin 1750  parts. 

Sodium  chloride 1200      " 

Iron 875      " 

"  From  this  we  obtained  a  metallic  mass  and  a  few  globules 
which  we  have  not  yet  analyzed." 

(See  also  Benzon's  process,  p.  325.) 

M.  Chenot,t  on  the  occasion  of  Deville's  first  paper  on  alumin- 
ium being  read  to  the  French  Academy,  Feb.  6,  1854,  announced 
that  in  1847,  by  reducing  earthy  oxides  by  means  of  metallic 

*  In  the  original  paper  it  is  given  as  12.09  per  cent.  iron.  The  inference  is 
unavoidable  that  this  was  a  misprint,  but  it  is  not  corrected  in  the  Errata  at 
the  end  of  the  volume. 

f  Comptes  Rendue,  xxxviii.  415. 


332  ALUMINIUM. 

sponges,  he  had  obtained  a  series  of  alloys  containing  up  to  40 
per  cent,  of  the  earth  metals.  He  cited  from  a  memoir  presented 
by  him  to  the  "  Societe  d' Encouragement"  in  1849,  in  which  he 
had  said,  "  on  taking  precipitates  of  the  earths,  they  are  all  reduced 
by  the  metallic  sponge  (e.  g.,  that  formed  by  reducing  iron  oxide 
in  a  current  of  carbonic  oxide  gas).  In  this  manner  I  have  made 
barides,  silicides,  aluminides,  etc.,  all  of  which  are  beautiful  silver- 
white,  very  hard  and  unoxidizable  in  air  or  in  contact  with  acid 
vapors.  They  are  fusible,  can  be  cast  and  work  perfectly  under 
the  hammer." 

Faraday  and  Stodart*  made  an  exhaustive  investigation  on  the 
preparation  of  iron-aluminium  alloys,  being  started  on  this  line 
by  finding  that  Bombay  "  wootz"  steel  contained  0.0128  to  0.0695 
per  cent,  of  aluminium,  while  no  metals  of  the  earths  were  to  be 
found  in  the  best  English  steels.  This  led  to  the  conclusion  that 
the  peculiar  properties  of  the  former,  especially  the  "  damasceen- 
ing,"  were  due  to  the  small  amount  of  aluminium.  These  scientists 
commenced  by  taking  pure  steel  or  sometimes  good  soft  iron  and 
intensely  heating  it  for  a  long  time  imbedded  in  charcoal  powder. 
Carbides  were  thus  formed,  having  a  very  dark  gray  color,  and 
highly  crystalline.  Average  analysis  of  this  product  gave  5.64 
per  cent,  carbon.  This  was  broken  and  powdered  in  a  mortar, 
mixed  intimately  with  pure  alumina  and  heated  in  a  closed  cru- 
cible for  a  long  time  at  a  high  temperature.  An  alloy  was  ob- 
tained of  a  white  color,  close  granular  texture  and  very  brittle, 
containing  3.41  per  cent,  of  aluminium,  with  some  carbon. 

When  40  parts  of  this  alloy  were  melted  with  700  parts  of  good 
steel  (introducing  0.184  per  cent,  of  aluminium)  a  malleable  but- 
ton was  obtained  which  gave  a  beautiful  damask  on  treatment 
with  acids  ;  while  67  parts  of  the  alloy  with  500  of  steel  (intro- 
ducing 0.4  per  cent,  of  aluminium)  gave  a  product  which  forged 
well,  gave  the  damask  and  "  had  all  the  appreciable  characters  of 
the  best  Bombay  wootz."  This  appears  to  be  very  strong  syn- 
thetic evidence  that  alumina  is  reduced  to  a  small  extent  even  in 
the  rude  hearths  in  which  the  Indian  steel  is  manufactured. 
Karsten,  however,  could  not  find  weighable  quantities  of  alu- 

*  Quarterly  Journal,  ix.  320. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  333 

minium  in  specimens  of  wootz,  nor  could  Henry,  a  very  expert 
analyst..  The  latter  suggested  that  Faraday  was  misled  by  the 
alumina  contained  in  intermingled  slag,  yet  the  latter  obtained 
alumina  without  silica  in  his  analyses.  In  the  light  of  more  re- 
cent developments  we  would  accept  Faraday's  results  as  being 
very  near  the  truth  in  the  matter. 

Ledebuhr*  quotes  an  analysis  made  by  Griiner  in  which  0.50 
per  cent,  of  aluminium  was  found  in  cast-iron  containing  besides 
2.30  per  cent,  of  carbon  and  2.26  per  cent,  of  silicon.  This 
would  tend  to  show  that  under  certain  conditions  iron  takes  up 
aluminium  in  the  blast-furnace.  Karsten,  however,  in  his  many 
analyses  of  malleable  iron,  steel  and  cast-iron  only  found  alu- 
minium in  unweighable  quantities.  Griiner  and  Lauf  stated 
that  aluminium  is  reduced  in  small  quantities  in  the  blast  furnace 
if  the  temperature  is  high  and  the  slag  basic ;  a  large  addition  of 
lime  thus  increases  the  reduction  of  alumina  and  hinders  that  of 
silica.  Most  pig  irons  contain  very  small  amounts  of  aluminium, 
but  some  English  varieties  contain  0.5  to  1.0  per  cent,  and  several 
Swedish  pig  irons  0.75  per  cent.  SchafhautlJ  found  as  much  as 
1.01  per  cent,  of  aluminium  in  a  grey  iron,  and  was  led  to  con- 
sider silicide  of  iron  and  aluminide  of  iron  as  characteristic  com- 
ponents of  grey  iron.  Lohage§  states  that  adding  alumina  in  the 
manufacture  of  cast-steel  has  a  great  influence  on  the  grain  and 
lustre  of  the  steel,  the  effect  being  doubtless  due  to  a  minute 
quantity  of  aluminium  taken  up.  Silicates  of  magnesium  and 
aluminium  are  formed  at  the  same  time  and  separating  out  float 
on  the  surface  of  the  molten  steel.  Corbin||  reports  2.38  per 
cent,  of  aluminium  in  chrome  steel,  but  Blair, 1"  of  Philadelphia, 
found  no  more  aluminium  in  chrome  than  in  other  steels.  This 
chemist  has  examined  many  irons  and  steels  particularly  for  alu- 
minium, and  reports  that  nearly  always  it  exists  as  such  in  steel, 
but  never  more  than  a  few  thousandths  of  a  per  cent.,  say  0.032 

*  Handbuch  der  Eisenhiittenkunde,  p.  265. 
f  Berg  u.  Hiittenmannische  Zeitung,  1862,  p.  254. 
J  Erdman's  Journal  fr.  Pr.  Chemie,  Ixvii.  257. 
§  Berg  u.  Hutteninannisclie  Zeitung,  1861,  p.  160. 
||  Silliman's  Journal,  1869,  p.  348. 
If  H.  M.  Howe,  E.  and  M.  J.  Oct.  29,  1887. 


334  ALUMINIUM. 

per  cent,  as  a  maximum.  He  has  further  been  unable  to  connect 
its  presence  with  any  peculiarity  in  the  properties  of  the  metal  or 
its  mode  of  manufacture. 

G.  H.  Billings,*  of  the  Norway  Iron  Works,  Boston,  made  the 
following  experiment  on  reducing  alumina  in  contact  with  iron  : — 
A  soft  iron  was  used  containing  a  trace  of  sulphur  and  phos- 
phorus, no  manganese  and  only  0.08  per  cent,  of  carbon.  The 
mixture  was  made  of 

12  parts  emery. 
18     "      alumina. 

1     "      pulverized  charcoal. 
36     "      fine  iron  turnings. 

These  were  mixed  thoroughly,  and  heated  to  whiteness  for  48 
hours.  The  metal  resulting  showed  a  solid,  homogeneous  fracture 
with  a  fine  crystalline  structure  resembling  steel  with  1  per  cent, 
of  carbon,  and  contained  on  analysis 

0.20  per  cent,  of  carbon. 
0.50       "  aluminium. 

It  was  also  found  that  if  this  quantity  of  aluminium  was  added  to 
a  pot  of  molten  iron  the  product  obtained  exhibited  the  same 
characteristics  as  the  above. 

Another  attempt  to  produce  iron-aluminium  alloys  directly  is 
stated  in  E.  Cleaver's  patent  specifications  as  follows  :f  Four  parts 
of  aluminium  sulphate  in  solution  are  mixed  with  one  part  of 
lamp-black,  the  mixture  dried  and  heated  to  the  highest  tempera- 
ture attainable  by  using  coal-gas  and  oxygen  in  a  lime-lined  fur- 
nace similar  to  those  used  for  melting  platinum.  Excess  of 
reducing  gas  is  maintained.  The  charge  is  cooled  in  the  furnace, 
removed,  mixed  with  twenty  times  its  weight  of  finely-divided 
cast-iron,  and  fused  in  a  steel  melting  furnace.  If  copper  is  used, 
a  bronze  results.  The  alloying  metal  may  be  added  in  the  gas 
furnace,  but  this  is  not  recommended  as  economical.  This  in- 
ventor also  claims  that  aluminium  ferrocyanide,  either  alone  or 
with  carbon,  can  be  decomposed  in  the  above-described  gas  fur- 
nace, yielding  a  rich  iron-aluminium  alloy.  As  a  higher  heat 

*  Transactions  American  Inst.  Mining  Engineers,  1877,  p.  452. 
f  English  Patent,  1276,  Jan.  26,  1887. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  335 

than  before  is  needed,  it  is  recommended  that  the  oxygen  be  pre- 
viously heated.  The  principal  difficulty  in  this  latter  process 
would  apparently  be  to  procure  the  aluminium  ferrocyanide  to 
operate  on. 

Mr.  Ostberg,*  connected  with  the  Mitis  process  for  making 
wrought-iron  castings,  stated  that  the  ferro-aluminium  used  in 
that  process  in  Sweden  was  made  by  adding  clays  to  iron  in 
process  of  smelting,  that  it  contained  7  to  8  per  cent,  of  alu- 
minium, and  could  be  made  very  cheaply.  Inquiries  made  for 
further  particulars  about  this  process  have  received  no  satisfac- 
tory reply,  and  there  is  no  outside  confirmation  of  the  above 
statement  to  be  found. 

Brin  Bros,  claim  that  they  can  alloy  aluminium  in  small  quan- 
tities with  iron  (see  p.  328).  Besides  the  processes  described  as 
most  suitable  for  producing  bronze,  they  also  state  that  if  soft 
strap-iron  is  coated  with  the  flux  composed  of  clay  and  salt  and 
heated  to  over  1000°  C.  in  a  muffle  or  a  blowpipe  flame/ the  iron 
absorbs  aluminium  and  becomes  tough  and  springy,  having  many 
of  the  properties  of  steel.  They  also  claim  that  by  simply  charg- 
ing broken  lumps  of  cast-iron  into  a  cupola  with  alternate  layers 
of  common  clay  and  a  flux,  the  metal  run  down  contains  as  much 
as  1.75  per  cent,  of  aluminium,  yielding  a  very  fluid,  strong  iron, 
which  runs  into  the  thinnest  castings.  The  London  papers  state 
that  the  alloys  thus  produced  assuredly  contain  aluminium,  and 
that  the  contained  aluminium  does  not  cost  over  25  cents  per  Ib. 

A  newspaper  report  speaks  of  exactly  similar  processes  being 
operated  by  an  aluminium  company  in  Kentucky.  (See  also 
p.  317.)  It  is  said  that  they  charge  a  cupola  with  scrap-iron, 
pig-iron,  coke,  clay,  and  a  flux,  and  that  on  melting  the  charge 
down  and  pouring,  the  castings  produced  are  similar  to  the  best 
steel,  the  fracture  of  the  metal  being  white,  slightly  fibrous  and 
free  from  blow-holes.  It  it  stated,  further,  that  the  castings,  on 
analysis,  contained  1.7  per  cent,  of  aluminium.  Scrap-iron  is 
also  treated  in  the  same  way  as  reported  by  Brin  Bros.,  being 
simply  coated  with  a  pasty  mixture  of  clay  and  a  flux  and  heated 
almost  white-hot,  when  the  iron  absorbs  aluminium. 

*  Eng.  and  Mining  Journal,  May  15,  1886. 


336  ALUMINIUM. 

The  Aluminium  Process  Company,  of  Washington,  D.  C., 
own  several  patents  granted  to  W.  A.  Baldwin,  of  Chicago,  111. 
In  one  of  these,*  a  bath  is  formed  by  fusing  together  4  parts  of 
ground  clay,  12  parts  of  common  salt  and  1  part  of  charcoal 
powder.  The  metal  to  be  alloyed,  e.  <?.,  an  iron  bar,  is  thrust  into 
the  bath,  which  is  not  hot  enough  to  melt  it,  and  allowed  to  re- 
main some  time,  with  occasional  stirring,  until  the  alloying  is 
complete.  In  the  case  of  metals  with  low  fusing  points  the  metal 
may  be  melted  with  the  mixture.  It  is  claimed  that  the  metal 
takes  up  a  small  percentage  of  aluminium.  With  a  more  highly 
aluminous  material  than  clay,  the  proportions  of  salt  and  carbon 
are  to  be  increased  proportionately.  In  a  modification  of  this 
process  adopted  for  foundry  practice,  f  a  mixture  of  clay,  salt  and 
carbon,  similar  to  the  above,  is  put  into  a  large  ladle  and  the 
molten  iron  tapped  directly  from  the  cupola  on  to  it.  A  brisk 
stirring  up  of  the  iron  takes  place,  much  scum  rises  to  the  sur- 
face, and  the  resulting  iron  is  more  fluid,  can  be  carried  further 
before  setting,  and  makes  sounder  and  stronger  castings  than 
similar  iron  not  treated.  The  resulting  iron  does  not  contain 
enough  aluminium  to  be  detected  by  quantitative  analysis.  Old- 
fashioned  fluxes  used  long  ago  in  foundries  were  similar  in 
composition  to  this  mixture  used  by  Baldwin,  and  were  found 
efficacious  in  freeing  dirty  iron  from  slag  and  other  impurities. 
It  is  hard  to  see  how  this  latter  process  is  anything  but  the  use 
of  a  common  flux,  with  a  different  explanation  as  to  how  it  acts — 
the  explanation  being  probably  the  most  questionable  part  of  the 
whole.  The  first-mentioned  process,  however,  has  the  merit  of 
novelty,  and  pieces  of  poor  iron  treated  by  it  are  made  springy 
and  much  like  steel,  but  whether  this  is  due  to  absorption  of 
aluminium  is  doubtful. 

The  Williams  Aluminium  Company,  of  New  York  City  (works 
at  Newark,  N.  J.),  manufacture  an  alloy  which  they  call  aluniin- 
ium-ferro-silicon  and  sell  for  foundry  use.  A  year  or  more  ago 
this  alloy  was  represented  to  contain  10  per  cent,  of  aluminium, 
but  several  analyses  disproved  this  and  recently  the  alloy  has 

*  English  Patent,  2584,  Feb.  21,  1888. 
f  U.  S.  Patent,  380161,  March  27,  1888. 


REDUCTION    BY   MISCELLANEOUS   AGENTS.  337 

been  sold  simply  on  the  guarantee  of  what  it  will  accomplish. 
The  metal  at  present  sold  by  this  company  does  contain  a  small 
amount  of  aluminium,  and  its  action  on  poor  foundry  iron  is 
similar  to  that  of  other  brands  of  ferro-aluminium ;  therefore,  as 
long  as  no  certain  percentage  of  aluminium  is  now  claimed,  the 
company  is  certainly  doing  a  legitimate  business.  (For  method  of 
using,  etc.,  see  Chap.  XVI.)  The  alloy  is  made  by  melting  down 
a  mixture  of  iron  filings,  clay,  salt,  charcoal,  and  another  flux 
whose  composition  is  not  divulged.  This  is  put  into  cast-iron 
pots  and  the  whole  charge,  crucibles  and  all,  run  down  in  a  fur- 
nace of  peculiar  design  constructed  by  Mr.  Williams.  The  capa- 
city of  the  plant  is  about  1000  Ibs.  of  alloy  a  day,  which  is 
broken  by  small  stamps  into  pieces  of  about  an  inch  diameter  and 
sold  at  10  cents  per  Ib.  Mr.  Williams  is  at  present  experimenting 
on  manufacturing  aluminium  bronze  by  the  same  methods,  and 
a  sample  piece  recently  forwarded  the  author  has  a  very  promising 
appearance. 

KEDUCTION  BY  OR  IN  PRESENCE  OF  ZINC. 

M.  Beketoif,*  was  not  able  to  reduce  vapor  of  aluminium 
chloride  by  vapor  of  zinc,  although  silicon  chloride  under  the 
same  conditions  was  readily  reduced. 

M.  Dullof  observes  that  the  double  chloride  of  aluminium  and 
sodium,  which  he  makes  directly  from  clay,  may  be  reduced  by 
zinc.  He  says,  "  the  reduction  by  zinc  presents  no  difficulties, 
but  it  is  less  easy  than  with  sodium.  An  excess  of  zinc  should 
be  employed,  which  may  be  got  rid  of  afterwards  by  distillation. 
The  metal  thus  prepared  possesses  all  the  characteristics  and  all 
the  properties  of  that  obtained  from  beauxite  with  sodium." 

M.  N.  Basset,J  a  chemist  in  Paris,  patented  a  somewhat  similar 
process  for  obtaining  aluminium.  If  the  statements  are  correct 
they  are  of  great  value.  The  paper  is  as  follows :  "  All  the 
metalloids  and  the  metals  which  form  by  double  decomposition 
proto-chlorides  or  sesqui-chlorides  more  fusible  or  more  soluble 

*  Bulletin  de  la  Societ6  Chemique,  1857,  p.  22. 
f  Bull,  de  la  Soc.  Chem.,  1860,  v.  472. 
J  Le  Genie  Industriel,  1862,  p.  152. 

22 


338  ALUMINIUM. 

than  aluminium  chloride  may  reduce  it  or  even  aluminium-sodium 
chloride.  Thus,  arsenic,  bismuth,  copper,  zinc,  antimony,  mercury, 
or  even  tin  or  amalgam  of  zinc,  tin,  or  antimony  may  be  em- 
ployed to  reduce  the  single  or  double  chloride.  The  author  em- 
ploys zinc  in  preference  to  the  others  in  consequence  of  its  low 
price,  the  facility  of  its  employment,  its  volatility,  and  the 
property  which  it  has  of  metallizing  easily  the  aluminium  as  it 
is  set  free.  "When  metallic  zinc  is  put  in  the  presence  of  alumin- 
ium-sodium chloride,  at  250  to  300°,  zinc  chloride,  ZuCl2,  is 
formed  and  aluminium  is  set  free.  This  dissolves  in  the  zinc 
present  in  excess,  the  zinc  chloride  combines  with  the  sodium 
chloride,  and  the  mass  becomes  little  by  little  pasty,  then  solid, 
while  the  alloy  remains  fluid.  If  the  heat  is  now  raised,  the  mass 
melts  anew,  the  zinc  reduces  a  new  portion  of  the  double  chloride 
and  the  excess  of  zinc  enriches  itself  in  aluminium  proportion- 
ately. These  facts  constitute  the  basis  of  the  following  general 
process:  One  equivalent  of  aluminium  chloride  is  melted, two  of 
sodium  chloride  added,  and  when  the  vapors  of  hydrochloric  acid 
are  dissipated,  four  equivalents  of  zinc,  in  powder  or  grain,  are 
introduced.  The  zinc  melts  rapidly,  and  by  agitation  the  mass 
of  chloride  thickens  and  solidifies.  The  mass  is  now  composed 
of  the  chlorides  of  aluminium,  zinc,  and  sodium,  and  remains  in 
a  pasty  condition  on  top  of  the  fluid  zinc  containing  aluminium. 
This  pasty  mass  is  removed,  piled  up  in  a  crucible  or  in  a  furnace, 
and  bars  of  the  fluid  alloy  of  zinc  and  aluminium  obtained  from 
a  previous  operation  are  placed  on  top  of  it.  This  is  gradually 
heated  to  bright  redness,  and  kept  there  for  an  hour.  The  melted 
mass  is  then  stirred  with  a  rake  and  poured  out.  It  is  an  alloy 
of  the  two  metals  in  pretty  nearly  equal  proportions.  This  alloy, 
melted  with  some  chloride  from  the  first  operation,  furnishes  alu- 
minium containing  only  a  small  per  cent,  of  zinc,  which  disappears 
by  a  new  fusion  under  aluminium  chloride  mixed  with  a  little 
fluoride,  providing  the  temperature  is  raised  to  a  white  heat  and 
maintained  till  the  cessation  of  the  vapors  of  zinc,  air  being  ex- 
cluded. 

"  The  metal  is  pure  if  the  zinc  employed  contained  no  foreign 
materials  or  metals.  It  is  melted  and  cast  into  ingots.  In  case 
the  zinc  contains  iron,  or  even  if  the  aluminium  chloride  contains 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  339 

some,  the  metallic  product  of  the  second  operation  may  be  treated 
with  dilute  sulphuric  acid  to  remove  it.  The  insoluble  residue  is 
washed  and  melted  layer  by  layer  with  fluorspar  or  cryolite  and 
a  small  quantity  of  aluminium-sodium  chloride,  intended  solely 
to  help  the  fusion." 

Mr.  Wedding,*  makes  the  following  remarks  on  this  process  : — 

"  It  is  some  time  since  Mr.  Basset  established  the  possibility  of 
replacing  sodium  by  zinc  in  the  manufacture  of  aluminium. 
Operating  on  aluminium-sodium  chloride  with  granulated  zinc, 
the  reduction  takes  place  towards  300°.  The  reduced  aluminium 
dissolves  in  the  excess  of  zinc,  while  the  zinc  chloride  formed 
combines  with  the  sodium  chloride,  forming  a  pasty  mass  if  the 
heat  is  not  raised.  Under  the  action  of  heat  the  alloy  enriches 
itself  in  aluminium,  because  the  zinc  volatilizes.  The  zinc  re- 
tained by  this  alloy  is  completely  eliminated  by  fusion  with 
double  chloride  and  a  little  fluorspar.  The  temperature  ought  to 
be  pushed  at  last  to  a  white  heat,  and  maintained  till  no  vapor  of 
zinc  escapes,  air  being  excluded  during  the  operation.  These 
results  I  have  confirmed,  having  submitted  the  experiments  of 
Mr.  Basset  to  an  attentive  examination,  and  I  recommend  its  use. 
However,  the  process  demands  very  much  precaution  because  of 
the  high  temperature  which  it  necessitates.  Another  chemist, 
Mr.  Specht,  even  in  1860  decomposed  aluminium  chloride  by 
zinc,  and  has  the  same  report  to  make — that  he  thinks  the  pro- 
cess will  be  some  time  advantageously  practised  on  a  large  scale." 

The  author  made  the  following  experiment  to  determine  if 
cryolite  would  be  reduced  by  zinc  :  One  pound  of  finely  powdered 
cryolite  was  melted  in  a  graphite  crucible  and  6  ounces  of  granu- 
lated zinc  dropped  into  it.  No  perceptible  reaction  took  place 
except  the  volatilization  of  zinc  when  the  crucible  was  uncovered, 
and  the  metal  obtained  after  15  minutes'  treatment  contained  on 
analysis  0.6  per  cent,  of  aluminium. 

Mr.  Fred.  J.  Seymourf  patented  the  reduction  of  aluminium  by 
zinc,  making  the  following  claim  :  An  improvement  in  extracting 
aluminium  from  aluminous  earths  and  ores  by  mixing  them  with 

*  Journal  de  Pharm.  [4]  iii.  p.  155  (1866). 
f  U.  S.  Pat.,  No.  291631,  Jan.  8,  1884. 


340  ALUMINIUM. 

an  ore  of  zinc,  carboniferous  material  and  a  flux,  and  subjecting 
the  mixture  to  heat  in  a  closed  retort,  whereby  the  zinc  is  liber- 
ated, is  caused  to  assist  in  bringing  or  casting  down  the  aluminium 
in  a  metallic  state,  and  the  alloy  of  aluminium  and  zinc  is  obtained. 
A  furnace  was  put  up  in  the  early  part  of  1884,  somewhere  in 
the  vicinity  of  Cleveland,  in  a  description  of  which  by  a  news- 
paper correspondent  we  are  told  that  steel  retorts  were  charged 
with  a  mixture  of  zinc  ore  100  parts,  kaolin  50,  carbon  (either 
anthracite  coal  or  its  equivalent  of  some  hydrocarbon)  125,  pearl- 
ash  15,  common  salt  10  ;  the  heat  necessary  being  about  1400°  C. 
In  a  second  patent*  Mr.  Seymour  claimed  that  by  heating  the 
same  mixture  in  a  retort  and  introducing  air  he  volatilized  oxides 
of  aluminium  and  zinc,  which  were  caught  in  a  condenser,  mixed 
with  carbon  and  reduced  in  a  crucible.  Immediately  after  the 
issue  of  this  patent,  the  American  Aluminium  Company  was 
organized  in  Detroit  with  a  capital  stock  of  $2,500,000,  to  operate 
the  patents  of  a  Dr.  Smith,  under  whose  name  processes  similar 
to  the  above  had  been  patented  in  Great  Britain  and  France.  A 
works  was  then  started  at  Findlay,  Ohio,  using  natural  gas  for 
fuel.  A  gentleman  who  saw  the  plant  described  it  as  a  rever- 
beratory  furnace,  into  which  a  charge  of  800  Ibs.  of  zinc  ore,  900 
of  native  alum,  and  300  of  charcoal  was  put.  On  heating  very 
strongly  by  gas  with  plenty  of  air  admitted,  zinc  oxide  was  vola- 
tilized (Mr.  Seymour  claimed  that  it  carried  alumina  with  it)  and 
was  condensed  by  passing  the  gases  through  large  copper  con- 
densers. This  fume  was  then  collected,  mixed  with  carbon  and 
a  metal,  and  run  down  in  a  crucible  to  an  alloy.  It  \vas  claimed 
that  the  plant  had  a  capacity  of  600  Ibs.  of  pure  aluminium  a  day, 
and  had  presumably  been  in  operation  over  a  year,  yet  there  was 
not  over  20  Ibs.  of  alloys  or  J  lb.  of  pure  aluminium  to  show  for 
it.  On  closer  inspection  so  plain  indications  of  fraud  were  visible 
in  the  last  part  of  the  operation  that,  although  veritable  aluminium 
alloys  were  taken  out  of  the  crucible,  the  gentleman  referred  to 
refused  to  believe  that  the  aluminium  was  produced  in  the  process. 
As  the  sequel  to  this  it  can  be  stated  that  in  the  middle  of  1889 
the  executive  committee  for  the  stockholders,  being  fully  satisfied 

*  U.  S.  Patent,  337996,  March  16,  1886. 


KEDTJCTION   BY   MISCELLANEOUS   AGENTS.  341 

of  the  worthlessness  of  the  process,  called  for  a  meeting  to  wind 
up  the  company.  One  month  later  Mr.  Seymour  died.  The 
story  went  the  rounds  of  the  daily  press  that  the  one  metallurgist 
who  commanded  the  secret  of  obtaining  cheap  aluminium  had 
died  taking  the  talisman  with  him,  and  a  vivid  picture  was  drawn 
of  the  manner  in  which  the  secret  had  been  preserved  by  means 
of  twelve-foot  palisades,  doubly-bolted  doors,  and  by  working  at 
the  midnight  hour.  Alas  !  the  secret  was  out  one  month  before  he 
died. 

A  method  of  reducing  cyanide  of  aluminium  by  means  of  zinc 
is  the  subject  of  a  patent  granted  F.  Lauterborn.*  Fourteen  parts 
of  aluminium  sulphate  dissolved  in  twice  its  weight  of  water  is  pre- 
cipitated by  thirteen  parts  of  ferro-cyanide  of  potassium  dissolved  in 
four  times  its  weight  of  water ;  the  precipitate  of  ferro-cyanide 
of  aluminium  is  collected  and  dried.  This  substance  is  then 
mixed  with  slightly  less  than  one-half  its  weight  of  dry,  anhy- 
drous sodium  carbonate,  put  in  a  crucible  and  ignited  with  as 
little  admission  of  air  as  possible.  The  ferro-cryanide  is  decom- 
posed, iron  carbide  separates  out,  and,  besides  sodium  cyanate, 
the  double  cyanide  of  aluminium  and  sodium  (APCy6  4-  3NaCy) 
is  obtained  as  a  melted  mass  which  is  poured  away  from  the 
heavier  iron  carbide  at  the  bottom  of  the  crucible.  If  two  parts 
of  this  salt  are  then  ignited  with  one  part  of  zinc  in  a  covered 
crucible,  aluminium  separates  as  a  regulus,  while  double  cyanide 
of  sodium  and  zinc  remains  as  slag.  The  slag  is  dissolved  in 
water  and  treated  with  metallic  iron,  whereby  metallic  zinc  is  pre- 
cipitated out  and  a  solution  of  ferro-cyanide  of  soda  remains  and 
can  be  used  over  in  the  process. 

I  do  not  know  whether  Lauterborn  has  ever  succeeded  in 
carrying  out  this  process ;  it  would  appear  at  the  very  beginning 
that  the  precipitation  of  aluminium  ferro-cyanide,  although  ap- 
pearing a  priori  possible,  has  always  been  found  impracticable, 
alumina  being  precipitated. 

J.  Clark,  of  Birmingham,  England,  has  taken  out  several  pat- 
ents in  England  and  one  in  Germany.  In  the  first,  f  hydrated 

*  German  Patent,  39915  (1887). 

f  English  Patent,  15946,  Dec.  6,  1886. 


342 


ALUMINIUM. 


aluminium  chloride  is  to  be  mixed  with  lime,  iron,  zinc,  ammonia, 
or  any  other  substance  which  combines  readily  with  chlorine,  and 
finely  divided  coke.  After  drying  the  mixture  it  is  introduced 
into  the  iron  blast  furnace  or  blown  into  the  Bessemer  converter, 
an  iron-aluminium  alloy  being  thus  produced.  In  a  second  pat- 
ent,* hydra  ted  aluminium  chloride  is  to  be  mixed  with  2J  parts 
of  granulated  zinc  and  1  part  of  iron  turnings  or  borings,  or  the 
alloy  of  the  zinc  and  iron  known  as  "  zinc  dross"  might  be  used. 
The  mass  is  let  stand  24  hours  and  dried.  The  orange-colored 
powder  resulting  is  mixed  with  borax  (!)  or  any  suitable  flux  and 
put  into  a  crucible  with  20  parts  of  fine  granulated  copper  and 
melted  down.  After  about  an  hour  the  zinc  and  iron  present 
have  probably  volatilized  as  chlorides,  while  aluminium  bronze 
remains.  When  the  copper  is  to  be  alloyed  in  large  quantities, 
it  may  be  melted  on  the  hearth  of  a  reverberatory  furnace  and  the 
prepared  powder  stirred  into  it. 

In  closing  the  subject  of  reduction  by  zinc,  I  would  state  that 
the  distillation  of  the  zinc  from  an  aluminium-zinc  alloy  appears 
to  be  quite  practicable.  My  friend,  Dr.  Lisle,  informs  me  that 
he  has  taken  a  highly  zinciferrous  alloy  and  brought  it  up  to 
98  per  cent,  aluminium  in  this  way. 

K EDUCTION   BY   LEAD. 

According  to  the  invention  of  Mr.  A.  E.  Wilde,  f  of  Netting 
Hill,  lead  or  sulphide-  of  lead,  or  a  mixture  of  the  two,  is  melted 
and  in  a  molten  state  poured  upon  dried  or  burnt  alum.  The 
crucible  in  which  the  mass  is  contained  is  then  placed  in  a  fur- 
nace and  heated,  with  suitable  fluxes.  The  metal,  when  poured 
out  of  the  crucible,  will  be  found  to  contain  aluminium.  The 
aluminium  and  lead  can  be  subsequently  separated  from  each 
other  by  any  known  means,  or  the  alloy  or  mixture  of  the  two 
metals  can  be  employed  for  the  various  useful  purposes  for  which 
lead  alone  is  more  or  less  unsuited. 

*  English  Patent,  10594,  Aug.  18,  1886  ;  German   Patent,  40205  (1887). 
f  Sci.  Am.  Suppl.,  Aug.  11,  1887. 


REDUCTION  BY  MISCELLANEOUS  AGENTS.  343 

REDUCTION  BY  MANGANESE. 

Walter  Weldon*  claimed  to  melt  together  cryolite  with  cal- 
cium chloride  or  some  other  non-metallic  chloride  or  sulphide, 
and  then  to  reduce  the  aluminium  chloride  or  sulphide  produced 
by  manganese,  also  adding  metallic  sodium  to  promote  the  reac- 
tion. It  is  not  probable  that  the  first  reaction  named  can  be 
produced,  but  the  latter  part,  as  far  as  the  manganese  is  con- 
cerned, may  succeed,  as  is  indicated  by  the  thermo-chemical  study 
of  the  reaction  (see  p.  191).  Of  course,  the  manganese  would 
have  to  be  used  as  ferro-manganese  or  spiegeleisen  and  an  iron 
alloy  produced.  Dr.  Green,  of  Philadelphia,  mixed  powdered 
spiegeleisen  with  cryolite,  placed  the  mixture  in  a  graphite  cru- 
cible and  heated  it  close  to  the  ports  of  an  open-hearth  steel  fur- 
nace until  it  softened,  yet  the  iron  contained  afterwards  only  0.3 
per  cent,  of  aluminium. 

REDUCTION  BY  MAGNESIUM. 

Magnesium  develops  more  heat  in  forming  compounds  than 
aluminium  does  (see  p.  186),  which  would  indicate  that  it  would 
reduce  aluminium  compounds  easily.  Only  one  or  two  state- 
ments on  this  point  can  be  found.  Margottetf  states  that  mag- 
nesium will  decompose  molten  cryolite,  setting  the  aluminium  at 
liberty.  R.  GratzelJ  patents  the  reduction  of  a  double  fluoride 
of  aluminium  and  potassium  or  sodium  by  metallic  magnesium, 
or  by  conducting  magnesium  vapor  into  the  liquid  compound. 

Roussin§  states  that  magnesium  does  not  precipitate  alu- 
minium in  a  metallic  state  from  its  solutions.  To  test  this  point 
I  placed  a  strip  of  magnesium  in  solution  of  aluminium  sul- 
phate, when  magnesium  sulphate  went  into  solution  and  a 
precipitate  of  alumina  was  formed.  It  is  apparent  that  the  alu- 
minium is  first  precipitated  in  the  metallic  state  and  promptly 
oxidized  by  the  water  as  fast  as  set  free,  in  a  manner  strictly 

*  English  Patent,  No.  97  (1883). 

f  Fremy's  Ency.  Chim. 

J  English  Patent,  14325,  Nov.  25,  1885. 

§  Jrnl.  de  Pharni.  et  de  Chhnie,  iii.  413. 


344  ALUMINIUM. 

analogous  to  the  production  of  alumina  at  the  negative  pole  when 
electrolyzing  aqueous  aluminium  solutions. 

The  only  other  reference  to  using  magnesium  as  a  reducing 
agent  is  in  a  patent  awarded  Count  R.  de  Montgelas,  of  Phila- 
delphia,* in  which  it  is  stated  that  aluminium  chloride  is  mixed 
with  litharge,  charcoal,  and  common  salt ;  fused  and  crushed. 
It  is  then  remelted  with  magnesium  filings  and  potassium  chlo- 
ride. After  cooling  it  is  again  crushed,  mixed  with  more  potas- 
sium chloride  and  nitrate  of  potash,  fused,  poured  into  water,  and 
the  globules  of  aluminium  separated  out. 

REDUCTION  BY  ANTIMONY. 

F.  Lauterbornf  proposes  to  decompose  aluminium  sulphide  by 
means  of  antimony  and  carbon.  One  hundred  parts  of  dried 
aluminium  sulphate  is  mixed  with  50  parts  of  charcoal  and  72 
parts  of  metallic  antimony ;  some  sodium  carbonate  and  fluorspar 
is  then  added,  and  the  mixture  melted.  It  is  claimed  that  anti- 
mony sulphide  and  aluminium  are  found  in  the  product,  the 
former  being  in  the  bottom  of  the  crucible.  In  a  modification  of 
this  process  it  is  claimed!  that  if  a  mixture  of  dried  aluminium 
sulphate,  sodium  carbonate,  and  antimony  sulphide  (stibnite)  is 
put  into  a  shaft  filled  with  incandescent  coke,  antimony  will  be 
first  set  free  by  the  reaction 

2Sb2S3  +  6Na2CO3  +  3C  «  6Na2S  +  9CO2  +  4Sb, 

and  that  these  products  act  further  on  the  aluminium  sulphate, 
setting  free  aluminium,  by  the  reaction 

2  A12(SO4)3  4. 6Na2S  +  4Sb  + 1 2C = 4Na2SbS3  +  4  Al  + 1 2CO2. 

The  sodium  sulph-antimonide  can  be  smelted  over  with  soda  and 
antimony  regained. 

These  extraordinary  formulas  have  little  or  no  basis  in  chemical 
science.  Dr.  Fischer§  says  plainly  that  they  are  false.  The 
author  tried  by  direct  experiment  to  reduce  aluminium  sulphide 
by  antimony,  fusing  down  a  mixture  of  powdered  antimony  with 

*  English  Patent,  10606,  Aug.  18,  1886. 
t  German  Patent,  32126  (1885). 
J  Dingier,  256,  226,  and  233. 
§  Wagner's  Jahresbericht,  1885. 


REDUCTION   BY   MISCELLANEOUS   AGENTS.  345 

aluminium  sulphide,  but  the  button  of  metal  obtained  did  not 
contain  a  trace  of  aluminium. 


EEDUCTION  BY  TIN. 

J.  S.  Howard  and  F.  M.  Hill,  assignors  to  the  Aluminium 
Product  Company,  of  New  York,  make  the  following  statements 
in  their  patent  specifications  :*  Some  aluminous  material  is  boiled 
in  muriatic  acid,  cooled,  mixed  with  Spanish  white  or  lime,  the 
free  acid  evaporated  off  at  a  high  temperature,  and  the  heat  finally 
increased  to  about  1000°  F.,  thereby  volatilizing  any  iron  present 
as  chloride.  The  product  thus  obtained  is  put  into  a  lime-lined 
crucible  along  with  lime,  charcoal,  fluorspar,  cryolite  and  potas- 
sium bisulphate,  the  whole  covered  with  chloride  of  tin,  and 
finally  by  common  salt.  This  is  subjected  to  a  smelting  tempera- 
ture, when  on  cooling  it  is  claimed  that  an  alloy  of  tin  and  alu- 
minium is  obtained.  To  separate  the  aluminium,  the  alloy  is 
melted  with  lead  or  bismuth,  which  alloy  with  the  tin,  letting  the 
aluminium  float  on  the  surface  along  with  oxides  and  other  im- 
purities. This  is  skimmed  off  and  purified  by  exposure  to  heat 
on  a  bed  of  porous  material. 

While  we  cannot  altogether  deny  the  possibility  of  metallic  tin 
reducing  aluminium  chloride,  yet  it  is  not  at  all  probable  that 
this  salt  remains  after  the  first  ignition.  It  is  also  improbable 
that  tin  would  reduce  cryolite  in  the  latter  operation,  but  there  is 
no  direct  evidence  to  contradict  the  above  statement. 

In  an  experiment  made  by  the  author,  aluminium  sulphide  was 
heated  with  tinfoil  for  a  short  time  at  a  red  heat.  The  resulting 
metal  contained  0.52  per  cent,  of  aluminium,  and  from  the  pro- 
portions of  tin  and  sulphide  used,  it  was  evident  that  a  large  part 
of  the  aluminium  sulphide  present  had  been  reduced. 

REDUCTION  BY  PHOSPHORUS. 

fL.  Grabau  patented  the  following  process,  in  1883,  but  has 
since  advocated  altogether  the  use  of  sodium,  showing  that  this 

*  U.  S.  Patent,  378136,  Feb.  21,  1888. 
f  English  Patent,  5798,  Dec.  18,  1883. 


346  ALUMINIUM. 

method  was  not  successful.  The  proposition  was  as  follows  : — 
A  rich  alloy  of  aluminium  and  phosphorus  is  made  by  melting 
the  two  elements  together  or  by  fusing  aluminium  with  phosphor 
salts  and  a  reducing  agent.  The  alloy  is  crushed,  mixed  with 
alumina  or  clay  or  aluminous  fluorides,  covered  with  coal-dust 
and  heated  to  incandescence  in  a  crucible.  It  was  claimed  that 
the  phosphorus  combined  with  the  oxygen  or  fluorine  of  the  alu- 
minous compound,  the  metal  produced  uniting  with  the  aluminium 
already  present.  To  produce  any  given  alloy,  the  phosphide  of 
the  required  metal  is  substituted  for  the  aluminium-phosphorus 
alloy.  Mr.  Grabau  broadens  out  his  specifications  into  more 
probable  fields  by  adding  that  "  manganesic  or  carburetted  metals 
may  be  used  instead  of  the  phosphide  alloys,  as  reducing  agents." 
It  is  almost  needless  to  say  that  the  generally  small  heat  of  com- 
bination of  phosphorus  compounds  would  show  that  the  reactions 
proposed  are  in  a  high  degree  improbable. 

REDUCTION  BY  SILICON. 

*M.  Wanner  makes  the  following  general  claims :  The  pro- 
duction of  aluminium  by  treating  a  fused  bath  of  aluminium 
fluoride  or  aluminous  fluorides,  while  in  a  molten  metallic  bath 
and  protected  from  oxidizing  agents,  with  a  reagent  whose  elements 
dissociate  below  the  fusing  point  of  the  aluminium  fluoride  or  the 
aluminous  fluorides,  and  having  one  element  of  such  affinity  that 
it  displaces  the  aluminium  in  the  fluoride  compound,  but  having 
no  element  capable  of  combining  with  the  reduced  aluminium. 
More  specifically,  sulphide  of  silicon  or  an  equivalent  reagent  is 
mentioned,  and  the  reaction  takes  place  on  the  hearth  of  a  short 
reverberatory  furnace,  the  metallic  bath  mentioned  being  prefer- 
ably metallic  iron  or  copper,  which  are  able  to  combine  with  the 
resulting  aluminium. 

The  reaction  proposed  is  so  far  out  of  the  usual  run  of  specula- 
tions that  no  opinion  can  be  hazarded  as  to  its  probability. 
Further,  silicon  sulphide  is  an  almost  unknown  compound,  and 

*  U.  S.  Patent,  410568,  Sept.  3, 1889. 


WORKING   IN   ALUMINIUM.  347 

it  would  be  very  interesting  to  know  how  it  is  to  be  prepared ; 
it  would  probably  be  a  more  difficult  feat  to  get  the  reagent  alone 
than  to  produce  aluminium  by  many  well-known  methods. 


CHAPTER  XIII. 
WORKING  IN  ALUMINIUM. 

MELTING  ALUMINIUM. 

DEVILLE  :  To  melt  aluminium  it  is  necessary  to  use  an  ordi- 
nary earthen  crucible  and  no  flux.  Fluxes  are  always  useless  and 
almost  always  harmful.  The  extraordinary  chemical  properties 
of  the  metal  are  the  cause  of  this ;  it  attacks  very  actively  borax 
or  glass  with  which  one  might  cover  it  to  prevent  its  oxidation. 
Fortunately  this  oxidation  does  not  take  place  even  at  a  high 
temperature.  When  its  surface  has  been  skimmed  of  all  impuri- 
ties it  does  not  tarnish.  Aluminium  is  very  slow  to  melt,  not 
only  because  its  specific  heat  is  considerable,  but  its  latent  heat 
appears  very  large.  It  is  best  to  make  a  small  fire  and  then  wait 
patiently  till  it  melts.  One  can  very  well  work  with  an  uncov- 
ered crucible. 

In  the  fusion  of  impure  aluminium,  very  different  phenomena 
are  observed  according  to  the  nature  of  the  foreign  metal  which 
contaminates  it.  Ferruginous  material  often  leaves  a  skeleton 
less  fusible  and  pretty  rich  in  iron  ;  a  liquation  has  taken  place, 
increasing  the  purity  of  the  melted  material.  When  the  alumin- 
ium contains  silicon,  this  liquation  is  no  longer  possible,  or  at 
least  it  is  very  difficult,  and  I  have  sometimes  seen  some  com- 
mercial aluminium  so  siliceous  that  the  workmen  were  unable  to 
remelt  it.  When  it  is  desired  to  melt  pieces  together,  they  can 
be  united  by  agitating  the  crucible  or  compressing  the  mass  with 
a  well-cleaned,  cylindrical  bar  of  iron.  Clippings,  filings,  etc., 
are  melted  thus :  Separate  out  first,  as  far  as  possible,  foreign 
metals,  and  to  avoid  their  combining  with  the  aluminium  heat  the 
divided  metal  to  as  low  a  heat  as  possible,  just  sufficient  to  melt 


348  ALUMINIUM. 

it.  The  oil  and  organic  matters  will  burn,  leaving  a  cinder, 
which  hinders  the  reunion  of  the  metal  if  one  does  not  press 
firmly  with  the  iron  bar.  The  metal  may  then  be  cast  very  easily 
and  there  is  found  at  the  bottom  of  the  crucible  a  little  cinder 
which  still  contains  a  quantity  of  aluminium  in  globules.  These 
may  be  easily  separated  by  rubbing  in  a  mortar  and  then  passing 
through  a  sieve,  which  retains  the  flattened  globules. 

Biederman  gives  the  following  directions  :  "The  whole  quan- 
tity of  metal  which  is  to  be  melted  must  not  be  put  into  the 
crucible  at  once,  but  little  by  little,  so  increasing  the  mass  from 
time  to  time  as  the  contents  become  fully  melted.  The  necessary 
knack  for  attaining  a  good  clean  melt  consists  in  dipping  the 
pieces  which  are  to  be  melted  together  in  benzine  before  putting 
in  the  crucible.  Mourey  even  pours  a  small  quantity  of  benzine 
into  the  crucible  after  the  full  melting  of  the  metal,  and  he  re- 
commends the  employment  of  benzine  in  the  melting  of  all  the 
noble  metals.  To  utilize  the  scrap  pieces  produced  in  working 
aluminium  into  various  useful  articles,  one  must  as  far  as  possible 
separate  out  first  the  pieces  which  have  been  soldered,  in  order 
that  the  newly  melted  aluminium  may  not  be  contaminated  by 
the  solder.  The  solder  adhering  to  these  pieces  can  be  removed 
by  treating  them  with  nitric  acid,  by  which  the  aluminium  is  not 
attacked." 

Aluminium  can  be  melted  with  perfect  safety  in  common  clay 
or  sand  crucibles  if  they  are  lined  with  carbon.  This  can  be 
done  by  mixing  lamp-black  to  a  paste  with  molasses,  plastering 
the  inside  of  the  crucible  evenly  and  drying  slowly  for  several 
days  at  a  moderate  temperature.  A  means  of  getting  a  more 
perfect  lining  is  to  ram  the  crucible  full  of  this  paste,  drying 
slowly  and  then  hollowing  out  a  cavity  of  the  required  size  leav- 
ing a  uniform  lining  of  sufficient  thickness.  In  using  these  car- 
bon-lined crucibles  they  should  be  kept  well-covered,  in  order 
that  the  carbon  may  not  burn  away  too  quickly,  taking  particular 
care  to  place  the  cover  on  when  the  metal  has  been  poured  out 
and  the  crucible  is  cooling  in  the  air.  Small  crucibles  may  be 
made  of  a  single  block  of  soapstone,  and  seem  to  last  a  long 
while,  the  aluminium  apparently  having  no  action  on  this 


WORKING   IN   ALUMINIUM.  349 

mineral  at  a  temperature  a  good  deal  higher  than  its  melting 
point. 

With  extra  care,  heating  in  a  furnace  where  the  heat  is  under 
exact  control,  aluminium  may  be  melted  in  sand  crucibles  or  in 
cast-iron  ones.  In  using  sand  or  Hessian  crucibles  no  flux  must 
be  added,  and  if  the  metal  is  heated  slowly  to  a  temperature  only 
enough  above  its  melting  point  to  admit  of  pouring  quickly,  it 
will  be  found  that  the  crucible  is  unattacked.  If,  however,  the 
crucible  is  heated  to  a  bright-red  heat  at  any  part,  it  will  be  found 
that  at  that  place  the  aluminium  has  attacked  the  crucible,  and 
on  pouring  out  the  metal  a  thin,  tough  skin  will  be  left  adhering  to 
the  spot  attacked  and  generally  taking  with  it  bits  of  the  wall 
when  it  is  forcibly  detached.  This  thin  sheet  is  hard,  tough,  and 
rich  in  silicon,  while  the  rest  of  the  metal  poured  out  has  also  ab- 
sorbed a  little  silicon.  An  iron  crucible  acts  in  precisely  the  same 
way ;  if  the  heat  is  kept  close  to  the  melting  point  of  aluminium  the 
latter  does  not  "wet"  the  iron,  but  at  a  bright-red  heat  it  attacks  it 
and  adheres,  as  in  the  case  of  the  sand  crucible.  I  will  repeat, 
that  if  the  temperature  is  kept  as  low  as  it  is  possible  to  melt  and 
cast  the'  metal,  and  if  no  fluxes  are  used,  neither  the  iron  or  sand 
crucibles  are  attacked. 

I  have  been  told  that  in  the  large  European  works,  where  500 
or  1000  Ibs.  of  aluminium  are  melted  at  once  on  the  bed  of  a 
reverberatory  furnace,  the  hearth  was  formerly  protected  by  pure 
beauxite,  closely  rammed  in  and  strongly  fired  before  using,  but 
basic  magnesia  bricks  have  now  been  substituted,  similar  to  those 
used  in  basic  open-hearth  furnaces  but  of  purer  materials,  and 
they  are  reported  as  being  all  that  can  be  desired  in  their  capacity 
for  resisting  corrosion. 

CASTING  ALUMINIUM. 

Deville :  "  Aluminium  can  be  cast  very  easily  in  metallic 
moulds,  but  better  in  sand  for  complicated  objects.  The  mould 
ought  to  be  very  dry,  made  of  a  porous  sand,  and  should  allow 
free  exit  to  the  air  expelled  by  the  metal,  which  is  viscous  when 
melted.  The  number  of  vents  ought  to  be  very  large,  and  a 
long,  perfectly  round  git  should  be  provided.  The  aluminium, 


350  ALUMINIUM. 

heated  to  redness,  ought  to  be  poured  rather  quickly,  letting  a 
little  melted  metal  remain  in  the  git  till  it  is  full,  to  provide  for 
the  contraction  of  the  metal  as  it  solidifies.  In  general,  this  pre- 
caution ought  to  be  taken  even  when  aluminium  is  cast  in  iron 
ingot  moulds  or  moulds  of  any  other  metal.  The  closed  ingot 
moulds  give  the  best  metal  for  rolling  or  hammmering.  By  fol- 
lowing these  precautions,  castings  of  great  beauty  may  be  ob- 
tained, but  it  is  not  advisable  to  conceal  the  fact  that  to  be  able 
to  succeed  completely  in  all  these  various  operations  requires  for 
aluminium,  as  for  all  other  metals,  a  special  familiarity  with  the 
material  which  practice  alone  is  able  to  give." 

The  peculiarity  of  molten  aluminium  which  a  metal  caster 
would  first  notice  is  its  viscousness,  that  is,  it  runs  thick.  When 
about  to  pour,  a  thick  edge  or  lip  of  metal  forms  which  must  in 
many  cases  be  punctured  in  order  to  start  the  metal  flowing.  On 
account  of  this  property  it  does  not  run  sharply  in  the  moulds  ex- 
cept where  a  head  of  metal  puts  it  under  pressure.  To  obtain 
sharp  castings  there  must  be  a  "  gate"  to  give  pressure  to  the 
metal,  and  when  we  remember  that  the  gravity  of  aluminium  is 
only  2.6  and  that,  besides,  it  does  not  flow  thinly,  it  will'  be  seen 
that  a  much  higher  head  of  metal  is  necessary  to  ensure  sharp 
castings  than  is  needed  for  iron,  brass,  etc.  A  small  slab  of  alu- 
minium two  inches  high  run  in  a  closed  iron  mould  with  very  little 
gate  was  quite  sharp  at  the  lower  end  but  had  rounded  corners 
at  the  top.  For  casting  in  closed  moulds,  the  best  results  as  to 
sharp  castings  free  from  cavities  are  obtained  if  a  slight  artificial 
pressure  can  be  applied  to  the  still  liquid  metal  in  the  mould 
immediately  after  pouring.  This  is  accomplished  by  Dr.  C.  0. 
Carroll,  of  New  York,  an  expert  in  making  cast-aluminium  den- 
tal plates,  by  closing  in  tightly  the  top  of  the  crucible  containing 
the  molten  aluminium  and  then  by  air  pressure  from  a  rubber 
bulb  forcing  the  metal  through  a  syphon-shaped  tube  terminating 
underneath  the  metal  and  connecting  tightly  with  the  pouring 
gate  of  the  mould.  The  mould  is  previously  heated,  in  order  not 
to  chill  the  metal  too  quickly,  and  when  the  metal  has  been 
forced  out  of  the  crucible  by  squeezing  the  bulb  the  pressure  is 
continued  for  a  short  time  in  order  to  force  the  metal  into  every 
crevice  of  the  mould  and  allow  the  casting  to  set  under  pressure. 


WORKING    IN   ALUMINIUM.  351 

The  idea  is  undoubtedly  correct,  and  the  excellently  sound  and 
extremely  sharp  castings  obtained  by  Dr.  Carroll  attest  its  success 
in  practice. 

PURIFICATION  OF  ALUMINIUM. 

Freeing  from  slag. — Deville  gives  the  following  information 
on  this  important  subject : — - 

"  It  is  of  great  importance  not  to  sell  any  aluminium  except 
that  which  is  entirely  free  from  the  slag  with  which  it  was  pro- 
duced and  with  which  its  whole  mass  may  become  impregnated. 
We  have  tried  all  sorts  of  ways  of  attaining  this  end,  so  as  to  ob- 
tain a  metal  which  would  not  give  any  fluorides  or  chlorides 
upon  boiling  with  water,  or  give  a  solution  which  would  be  pre- 
cipitated by  silver  nitrate.  At  Glaciere  we  granulated  the  metal 
by  pouring  it  while  in  good  fusion  into  water  acidulated  with 
sulphuric  acid  ;  this  method  partially  succeeded.  But  the  process 
which  M.  Paul  Morin  uses  at  present  (1859),  and  which  seems  to 
give  the  best  results,  is  yet  simpler.  Three  or  four  kilos  of  alu- 
minium are  melted  in  a  plumbago  crucible  without  a  lid,  and 
kept  a  long  time  red  hot  in  contact  with  the  air.  Almost  always 
acid  fumes  exhale  from  the  surface,  indicating  the  decomposition 
by  air  or  moisture  of  the  saline  matter  impregnating  the  metal. 
The  crucible  being  withdrawn  from  the  fire,  a  skimmer  is  put 
into  the  metal.  This  skimmer  is  of  cast  iron  ;  its  surface  ought 
not  to  be  rough  and  it  will  not  be  wetted  by  the  aluminium  in 
the  least  during  the  skimming ;  it  may  be  of  advantage  to  oxidize 
its  surface  with  nitre  before  using.  The  white  and  slaggy  mat- 
ters are  then  removed,  carrying  away  also  a  little  metal,  and  are 
put  aside  to  be  remelted.  So,  in  this  purification,  there  is  really 
no  loss  of  metal.  After  having  thus  been  skimmed,  the  alumin- 
ium is  cast  into  ingots.  This  operation  is  repeated  three  or  four 
times  until  the  metal  is  perfectly  clean,  which  is,  however,  not 
easily  told  by  its  appearance,  for,  after  the  first  fusion,  the  crude 
aluminium  when  cast  into  ingots  has  a  brilliancy  and  color  such 
as  one  would  judge  quite  irreproachable,  but  the  metal  would  not 
be  clean  when  it  was  worked,  and  especially  when  polished 
would  present  a  multitude  of  little  points  called  technically 


352  ALUMINIUM. 

'  piqiires/  which  give  to  its  surface,  especially  with  time,  a  dis- 
agreeable look.  Aluminium,  pure  and  free  from  slag,  improves 
in  color  on  using.  It  is  the  contrary  with  the  impure  metal  or 
with  aluminium  not  freed  from  slag.  When  aluminium  is  sub- 
mitted to  a  slow,  corroding  action,  its  surface  will  cover  itself 
uniformly  with  a  white,  thin  coating  of  alumina.  However,  any 
time  that  this  layer  is  black  or  the  aluminium  tarnishes,  we  may 
be  sure  that  it  contains  a  foreign  metal  and  that  the  alteration  is 
due  to  this  impurity." 

Freeing  from  impurities. — Again  Deville  is  the  authority,  and 
we  quote  his  advice  on  the  subject : — 

"  A  particular  characteristic  of  the  metallurgy  of  aluminium  is 
that  it  is  necessary,  in  order  to  get  pure  metal,  to  obtain  it  so  at 
the  first  attempt.  When  it  contains  silicon,  I  know  of  no  way 
to  eliminate  it,  all  the  experiments  which  I  have  made  on  the 
subject  have  had  a  negative  result ;  simple  fusion  of  the  metal  in 
a  crucible,  permitting  the  separation  by  liquation  of  metals  more 
dense,  seems  rather  to  increase  the  amount  of  silicon  than  to  de- 
c.ease  it.  When  the  aluminium  contains  iron  or  copper,  each 
fusion  purifies  it  up  to  a  certain  limit,  and  if  the  operation  is  done 
at  a  low  heat  there  is  found  at  the  bottom  of  the  crucible  a  metal- 
lic skeleton  containing  much  more  iron  and  copper  than  the 
primitive  alloy.  At  first  I  made  this  liquation  in  the  muffle  of 
a  cupel  furnace,  in  which  process  the  access  of  air  permitted  the 
partial  oxidation  of  these  two  metals.  The  little  lead  which  alu- 
minium may  sometimes  take  up  may  thus  be  easily  separated. 
Unfortunately,  the  process  does  not  give  completely  satisfactory 
results.  It  is  the  same  in  fusing  impure  aluminium  under  a 
layer  of  potassium  sulphide,  K2S3 ;  there  is  a  partial  separation 
of  the  lead,  copper,  and  iron.  That  which  has  succeeded  best 
with  us  is  the  process  which  we  have  employed  for  a  long  time  at 
Glaciere,  and  which  consists  in  melting  the  aluminium  under 
nitre  in  an  iron  crucible.  We  have  in  this  way  improved  the 
quality  of  large  quantities  of  aluminium.  The  operation  is  con- 
ducted as  follows :  Aluminium  has  generally  been  melted  with 
nitre  in  order  to  purify  it  by  means  of  the  strong  disengagement 
of  oxygen  at  a  red  heat,  no  doubts  being  entertained  as  to  the 
certainty  of  the  result.  But  it  is  necessary  to  take  great  care 


WORKING   IN    ALUMINIUM.  353 

when  doing  this  in  an  earthen  crucible.  The  silica  of  the  crucible 
is  dissolved  by  the  nitre,  the  glass  thus  formed  is  decomposed  by 
the  aluminium,  and  the  siliceous  aluminium  thus  formed  is,  as  we 
know,  very  oxidizable,  and  especially  in  the  presence  of  alkalies. 
So,  the  purification  of  aluminium  by  nitre  ought  to  be  done  in  a 
cast-iron  crucible  well  oxidized  itself  by  nitre  on  the  inside. 

"  On  melting  aluminium  containing  zinc  in  contact  with  the 
air  and  at  a  temperature  which  will  volatilize  the  zinc,  the  largest 
part  of  the  latter  burns  and  disappears  as  flaky  oxide.  To  obtain 
a  complete  separation  of  the  two  metals  it  is  necessary  to  heat 
the  alloy  to  a  high  temperature  in  a  brasqued  crucible.  This 
experiment  succeeds  very  well,  but  it  is  here  shown  that  the  alu- 
minium must  oxidize  slightly  on  its  surface,  for  some  carbon  is 
reduced  by  the  aluminium  from  the  carbonic  oxide  with  which 
the  crucible  is  filled.  This  carbon  thus  separated  is  quite  amor- 
phous." 

Dr.  Lisle,  of  Springfield,  O.,  tested  the  removal  of  zinc  from 
aluminium  by  distillation  and  succeeded  in  obtaining  a  product 
with  98  per  cent,  of  aluminium  from  which  the  zinc  had  been 
completely  removed.  If  aluminium  containing  tin  is  melted 
with  lead,  the  latter  sinks  with  the  tin,  removing  it  almost  com- 
pletely from  the  aluminium,  but  the  metal  remaining  retains  a 
little  lead.  In  an  experiment  made  by  the  author,  aluminium 
with  10  per  cent,  of  tin  was  treated  in  this  way,  but  the  aluminium 
retained  nearly  7  per  cent,  of  lead,  giving  it  a  blue  color  and  large 
crystalline  structure.  M.  Peligot  is  reported  by  Deville  to  have 
succeeded  in  cupelling  aluminium  with  lead,  whereby  impure, 
tough  metal  became  quite  malleable.  It  may  be  that  the  small 
percentage  retained  by  aluminium  when  melted  with  lead  is  re- 
moved by  fusion  on  a  cupel,  but  I  have  been  unable  to  perform 
any  operation  with  aluminium  at  all  analogous  to  the  cupellation 
of  silver  with  lead. 

G.  Buchner  states  that  commercial  aluminium  contains  con- 
siderable quantities  of  silicon,  which  by  treatment,  when  melted, 
with  hydrogen  evolves  hydrogen  silicide.  This  does  not  result  if 
arsenic  is  present. 

To  test  this  point,  I  took  a  sample  of  aluminium  containing  4 
per  cent  of  silicon,  and  94  per  cent,  of  aluminium.  This  was 

23 


354  ALUMINIUM. 

melted  in  a  sand  crucible  and  hydrogen  gas  run  in  for  12  min- 
utes. On  pouring  out,  the  crucible  was  unattacked,  but  the 
metal  was  identical  in  color  and  structure  with  that  not  treated. 
This  was  repeated  several  times,  hydrogen  gas  being  passed  in  as 
long  as  20  minutes  with  the  metal  at  red  heat,  but  no  apparent 
change  in  the  purity  of  the  metal  resulted. 

Similar  experiments  were  made  with  a  current  of  sulphuretted 
hydrogen  gas,  with  a  view  of  removing  the  iron.  No  improve- 
ment in  the  looks  of  the  aluminium  was  apparent.  If,  however, 
air  was  blown  into  the  melted  metal,  an  improvement  was  made. 
The  aluminium  was  at  a  bright  red  heat,  and  air  blown  in  for  5 
minutes,  at  the  end  of  which  time  about  5  to  10  per  cent,  of 
dross  composed  of  mixed  metal  and  oxide  was  formed,  but  the 
remaining  metal  was  whiter,  of  a  finer  grain  and  evidently  much 
improved. 

Prof.  Mallet*  made  some  very  accurate  estimations  of  the 
atomic  weight  of  aluminium  (which  he  found  to  be  27.02),  and 
obtained  the  chemically  pure  metal  required  for  his  work  by  the 
following  process,  which  is  quite  applicable  when  studying  the 
properties  of  the  pure  metal,  yet  is,  of  course,  altogether  out  of 
the  question  as  an  industrial  operation.  The  purest  commercial 
metal  was  bought,  and  on  analysis  was  found  to  contain — 

Aluminium 96.89  per  cent. 

Iron        .  1.84       " 

Silicon   .         . 1.27       " 

This  was  treated  with  liquid  bromine  and  converted  into  bromide. 
This  salt  was  then  purified  by  fractional  distillation,  the  tempera- 
ture being  very  carefully  regulated,  and  the  operation  repeated 
until  the  product  was  perfectly  colorless,  and  dissolved  in  water 
without  leaving  any  perceptible  impurity.  The  reduction  was  ac- 
complished with  difficulty  and  much  loss  by  treating  with  sodium 
in  a  crucible  made  of  a  mixture  of  pure  alumina  and  sodium 
aluminate.  The  metal  obtained  gave  on  analysis  no  weighable 
quantity  of  impurities,  and  the  properties  mentioned  in  Chapters 
III.  and  IV.  are  those  quoted  from  Mallet's  report. 

*  Philosophical  Magazine,  1880. 


WORKING  IN  ALUMINIUM.  355 

ANNEALING. 

By  heating  to  redness  and  cooling  quickly,  as  by  dropping  into 
water,  aluminium  becomes  soft.  To  get  the  best  results,  the 
metal  should  be  heated  until  it  just  begins  to  glow,  or  the  object 
is  rubbed  with  a  lump  of  fat,  and  the  moment  that  the  black 
trace  left  by  the  carbonization  of  the  fat  disappears,  the  metal  is 
removed  from  the  annealing  oven.  Great  care  is  necessary  in 
annealing  thin  sheets  which  are  being  beaten  into  leaf,  to  avoid 
melting  them.  Fine  wire  can  be  annealed  over  the  chimney  of 
an  Argand  burner. 

HARDENING. 

By  hammering,  rolling,  or  drawing,  aluminium  becomes  sen- 
sibly harder  and  stiffer;  also,  by  long,  gradual  cooling  the  same 
result  is  obtained,  so  that  it  becomes  elastic  enough  to  be  used 
even  for  hair-springs  for  watches. 

EOLLING. 

Before  rolling  a  bar  of  aluminium  it  is  well  to  soften  it,  and 
to  taper  down  a  "  lead"  by  hammering.  The  metal  forges  well 
under  the  hammer  at  a  low-red  heat.  The  metal  for  rolling  had 
better  be  -cast  into  plates  in  covered  iron  ingot-moulds,  and  the 
surfaces  planed  to  remove  small  irregularities.  The  rolling  is  not 
difficult,  except  that  a  large  amount  of  power  is  required  (about 
as  much  for  cold  aluminium  as  for  hot  steel),  and  as  the  metal 
quickly  gets  hard  it  must  be  annealed  often.  It  is  recommended 
that  the  metal  be  brought  warm  under  the  rolls,  and,  if  possible, 
elongated  10  to  20  per  cent,  with  the  first  pass,  in  order  to  en- 
tirely destroy  the  crystalline  structure  of  the  metal.  The  anneal- 
ing is  repeated  between  each  pass  until  the  sheet  is  about  3  milli- 
metres thick,  after  which  it  can  generally  be  rolled  with  fewer 
annealings,  sometimes  without  any  at  all.  Rolls  warmed  to  100- 
150°  work  better  than  cold  ones.  Aluminium  has  been  rolled 
down  to  the  thinness  of  tissue-paper. 

Thin  rolled  sheets  may  be  still  further  extended  out  by  beating 
into  leaf.  The  gold-beaters  are  said  to  have  no  special  difficulty 


356  ALUMINIUM. 

in  doing  this,  except  that  more  frequent  annealings  are  necessary 
than  with  gold  or  silver.  M.  Degousse  was  the  first  to  ma'ke 
this  leaf,  in  1859 ;  he  states  that  the  tempering  must  be  done  by 
warming  only  to  100°  or  150°,  an  actual  glowing  heat  proving 
very  unsuitable.  Aluminium  leaf  is  made  as  thin  as  ordinary 
gold  or  silver  leaf,  and  this  property  would,  therefore,  establish 
aluminium  as  next  to  these  noble  metals  in  the  order  of  malle- 
ability. 

DRAWING. 

Prof.  Thurston  places  aluminium  as  sixth  in  the  order  of  duc- 
tility, being  preceded  by  gold,  silver,  platinum,  iron,  and  copper, 
but  it  is  doubtful  if  it  does  not  rank  equally  as  high  as  iron. 
Deville  states  that  in  1855  M.  Yangeois  obtained  very  fine  wire 
with  metal  far  from  being  pure.  Bell  Bros.,  at  Newcastle-on- 
Tyne,  recommended  that  the  metal  for  drawing  be  run  into  an 
open  mould  so  as  to  form  a  flat  bar  of  about  one-half  inch  sec- 
tion, the  edges  of  which  are  beaten  very  regularly  with  a  hammer. 
The  diameter  should  be  very  gradually  reduced  at  first,  with  fre- 
quent heating.  When  the  threads  are  required  very  fine  the 
heating  becomes  a  very  delicate  operation,  on  account  of  the  fine- 
ness of  the  threads  and  the  fusibility  of  the  metal.  The  gauge 
should  be  reduced  by  the  smallest  possible  gradations,  when  wires 
may  be  obtained  as  fine  as  a  hair. 

Aluminium  tubes  are  drawn,  either  round  or  square,  from  sheet 
which  has  been  soldered  together  or  from  cast  rings  of  the  re- 
quired section  ;  the  first  method  is  said  to  be  preferred.  As  the 
aluminium  quickly  loses  its  temper  it  must  be  annealed  after  each 
extension. 

STAMPING  AND  SPINNING. 

Aluminium  can  be  spun  on  the  lathe  into  all  sorts  of  round 
and  hollow  forms ;  it  may  also  be  pressed  or  stamped  into  shape 
in  the  cold ;  it  is  of  advantage  in  doing  this  to  use  a  kind  of  var- 
nish composed  of  4  parts  of  oil  of  turpentine  and  1  part  of  stearic 
acid.  Soap-water  is  always  to  be  avoided. 


WORKING  IX  ALUMINIUM.  357 

GRINDING,  POLISHING  AND  BURNISHING. 

When  cast  carefully  it  can  be  filed  without  fouling  the  file. 
Spun  and  stamped  articles  of  aluminium  can  easily  be  ground  by 
using  olive  oil  and  pumice.  Biederman  makes  the  following  re- 
marks on  polishing :  "  The  use  of  the  old  means  of  polishing  and 
burnishing  metals,  such  as  soap,  wine,  vinegar,  linseed-oil,  decoc- 
tion of  marshmallow,  etc.,  is  not  effective  with  aluminium,  but, 
on  the  contrary,  is  even  harmful ;  because,  using  them,  the  blood 
stone  and  the  burnishing  iron  tear  the  metal  as  fine  stone  does 
glass.  Oil  of  turpentine  has  also  been  used,  but  with  no  good 
effect.  Mourey  found,  after  many  attempts,  that  a  mixture  of 
equal  weights  of  olive  oil  and  rum,  which  were  shaken  in  a  bot- 
tle till  an  emulsified  mass  resulted,  gave  a  very  brilliant  polish. 
The  polishing  stone  is  dipped  in  this  liquid,  and  the  metal  pol- 
ished like  silver,  except  that  one  must  not  press  so  hard  in  shin- 
ing up.  The  peculiar  black  streaks  which  form  under  the  polish- 
ing stone  need  cause  no  trouble;  they  do  not  injure  the  polish  in 
the  least,  and  can  be  removed  from  time  to  time  by  wiping  with 
a  lump  of  cotton.  The  best  way  to  clean  a  soiled  surface  and  re- 
move grease  is  to  dip  the  object  in  benzine,  and  dry  it  in  fine 
sawdust." 

Mr.  J.  Richards  found  that  when  buffing  in  the  ordinary  way 
the  dark-colored  burnishing  powder  cut  into  the  metal  and  filled 
its  pores  with  black  specks.  The  best  means  of  burnishing  is  to 
use  a  piece  of  soft  wood  soaked  in  olive  oil,  this  closes  the  grain 
and  gives  a  most  brilliant  finish. 

ENGRAVING. 

Kerl  &  Stohman  :  Aluminium  resists  the  action  of  the  engrav- 
ing tool,  which  slides  upon  the  surface  of  the  metal  as  upon  hard 
glass.  But  as  soon  as  a  varnish  of  4  parts  of  oil  of  turpentine 
and  1  of  stearic  acid,  or  some  olive  oil  mixed  with  rum  is  used, 
the  tool  cuts  into  it  as  into  pure  copper. 


358  ALUMINIUM. 

MAT. 

Deville  :  "  Aluminium,  like  silver,  is  able  to  take  a  very  beauti- 
ful mat  which  keeps  indefinitely  in  the  air.  It  is  obtained  easily 
by  plunging  the  surface  for  an  instant  in  a  very  dilute  solution  of 
caustic  soda,  washing  in  a  large  quantity  of  water  and  at  last  dip- 
ping in  strong  nitric  acid.  Under  these  conditions,  all  the  foreign 
materials  which  might  contaminate  it,  except  silicon  in  large  pro- 
portion, dissolve  and  leave  the  metal  quite  white  and  with  a  very 
pleasing  appearance."  Bell  Bros,  recommend  first  washing  the 
objects  in  benzole  or  essence  of  turpentine  before  treatment  with 
caustic  soda. 

SOLDERING  ALUMINIUM. 

At  the  time  Deville  wrote  his  book,  the  difficulty  of  soldering 
aluminium  properly  was  one  of  the  greatest,  if  not  the  greatest, 
obstacle  to  the  employment  of  the  metal.  His  views  on  the  ques- 
tion may  be,  therefore,  very  interesting ;  they  are  as  follows  : — 

"  Aluminium  may  be  soldered,  but  in  a  very  imperfect  manner, 
either  by  means  of  zinc,  or  cadmium,  or  alloys  of  aluminium 
with  these  metals.  But  a  very  peculiar  difficulty  arises  here,  we 
know  no  flux  to  clean  the  aluminium  which  does  not  attack  the 
solder,  or  which,  protecting  the  solder,  does  not  attack  the  alu- 
minium. There  is  also  an  obstacle  in  the  particular  resistance  of 
aluminium  to  being  wetted  by  the  more  fusible  metals,  and  on 
this  account  the  solder  does  not  run  between  and  attach  itself  to 
the  surfaces  to  be  united.  M.  Christofle  and  M.  Charriere  made, 
in  1855,  during  the  Exposition,  solderings  with  zinc  or  tin.  But 
this  is  a  weak  solder  and  does  not  make  a  firm  seam.  MM.  Tis- 
sier,  after  some  experiments  made  in  my  laboratory,  proposed 
alloys  of  aluminium  and  zinc,  which  did  not  succeed  any  better. 
However,  M.  Denis,  of  Nancy,  has  remarked  that  whenever  the 
aluminium  and  the  solder  melted  on  its  surface  are  touched  by  a 
piece  of  zinc,  the  adhesion  becomes  manifest  very  rapidly,  as  if 
a  particular  electrical  state  was  determined  at  the  moment  of  con- 
tact. But  even  this  produces  only  weak  solderings  insufficient 
in  most  cases. 


WORKING    IN    ALUMINIUM.  359 

A  long  time  ago,  M.  Hulot  proposed  to  avoid  the  difficulty  by 
previously  covering  the  piece  with  copper,  then  soldering  the 
copper  surfaces.  To  effect  this,  plunge  the  article,  or  at  least  the 
part  to  be  soldered,  into  a  bath  of  acid  sulphate  of  copper.  Put 
the  positive  pole  of  a  battery  in  communication  with  the  bath, 
and  with  the  negative  pole  touch  the  places  to  be  covered,  and  the 
copper  is  deposited  very  regularly.  M.  Mourey  has  succeeded  in 
soldering  aluminium  by  processes  yet  unknown  to  me ;  samples 
which  I  have  seen  looked  excellent.  I  hope,  then,  that  this  pro- 
blem has  found,  thanks  to  his  ingenuity,  a  solution  ;  a  very  im- 
portant step  in  enlarging  the  employment  of  aluminium." 

Mourey's  first  practicable  solders  for  aluminium  were  of  zinc 
and  aluminium  and  of  two  kinds — hard  and  soft.  He  used  a 
soft  solder  to  first  unite  the  pieces  and  afterwards  finished  the 
soldering  with  a  less  fusible  one.  These  solders  contained — 

I.  II.         III.         IV.          V. 

Aluminium   ....     20         15         12  8  6 

Zinc 80        85        88        92        94 

The  alloys  with  the  larger  proportion  of  zinc  are  the  easiest  melt- 
ing or  softest  ones,  one  such  as  IV  being  used  for  ordinary  work, 
while  II  was  used  for  brazing.  These  solders  have  the  disad- 
vantage that  on  melting  they  oxidize  very  easily,  and  in  conse- 
quence of  the  film  of  oxide  thus  formed  the  work  is  so  much 
more  difficult.  This  difficulty  can  be  overcome  by  dipping  the 
small  grains  of  solder  in  copaiva  balsam  and  turpentine,  which 
keep  out  the  air  and  act  as  reducing  agents  during  the  operation. 
The  new  solders  subsequently  used  were  simpler  in  application, 
for  the  work  was  finished  with  one  solder  and  the  moistening 
with  balsam  was  rendered  unnecessary. 

Mourey  improved  upon  the  zinc-aluminium  solders  by  adding 
copper,  using  five  different  alloys  of  these  three  metals  according 
to  the  objects  to  be  soldered.  They  contained — 

I.  II.  III.  IV.  V. 

Aluminium  ....     12  9           7  6  4 

Copper           ....       8  6           5  4  2 

Zinc 80  85  88  90  94 

The  following  directions  are  given  for  preparing  these  alloys  : — * 
*  Das  Lothen,  by  Edmund  Schlosser,  Vienna,  1880,  p.  101. 


360  ALUMINIUM. 

"  To  make  the  solder,  first  put  the  copper  in  the  crucible.  When 
it  is  melted,  then  add  the  aluminium  in  three  or  four  portions, 
thereby  somewhat  cooling  the  melted  mass.  When  both  metals 
are  melted,  the  mass  is  stirred  with  a  small  iron  rod,  and  then  the 
required  quantity  of  zinc  added,  free  from  iron,  and  as  clean  as 
possible.  It  melts  very  rapidly.  The  alloy  is  then  stirred 
briskly  with  an  iron  rod  for  a  time,  some  fat  or  benzine  being  mean- 
while put  in  the  crucible  to  prevent  contact  of  the  metal  with  air 
and  oxidation  of  the  zinc.  Finally  the  whole  is  poured  out  into 
an  ingot  mould  previously  rubbed  with  benzine.  After  the  addi- 
tion of  zinc,  the  operation  must  be  finished  very  rapidly,  because 
the  latter  will  volatilize  and  burn  out.  As  soon  as  the  zinc  is 
melted,  the  crucible  is  taken  out  of  the  fire.  Only  zinc  free  from 
iron  can  be  used,  since  even  an  apparently  insignificant  amount 
of  this  impurity  injures  the  qualities  of  the  solders  very  materi- 
ally in  regard  to  durability  and  fusibility. 

"  The  separate  pieces  of  metal  to  be  soldered  together  are  first 
well  cleaned,  then  made  somewhat  rough  with  a  file  at  the  place 
of  juncture,  and  the  appropriate  solder  put  on  it  in  pieces  about 
the  size  of  millet  grains.  The  objects  are  laid  on  some  hot  char- 
coal, and  the  melting  of  the  solder  effected  by  a  blast  lamp  or 
a  Rochemont  turpentine-oil  lamp.  During  the  melting  of  the 
solder,  it  is  rubbed  with  a  little  soldering  iron  of  pure  aluminium. 
The  soldering  iron  of  pure  aluminium  is  essentially  a  necessity 
for  the  success  of  the  operation,  since  an  iron  of  any  other  metal 
will  alloy  with  the  metals  composing  the  solder,  while  the  melted 
solder  does  not  stick  to  the  iron  made  of  aluminium. 

"For  quite  small  objects,  as  for  jewelry,  solder  I  is  used;  for 
larger  objects  and  ordinary  work  IV  is  more  suitable,  and  is  the 
solder  most  used.  These  alloys  work  so  perfectly  that  plates 
soldered  together  never  break  at  the  joint  when  bent  back  and 
forth,  but  always  give  way  in  other  places ;  which  is  a  result  not 
always  possible  in  the  best  soldering  of  plates  of  silver." 

Bell  Bros,  used  the  above  solders  in  their  works  at  Newcastle, 
and  in  a  description  of  the  soldering  operation  state  the  following 
facts  in  addition  to  those  already  given  :*  "  In  the  operation  of 

*  Chemical  News,  iv.  81. 


WORKING   IN   ALUMINIUM.  361 

soldering,  small  tools  of  aluminium  are  used,  which  facilitate  at 
the  same  time  the  fusion  of  the  solder  and  its  adhesion  to  the  pre- 
viously prepared  surfaces.  Tools  of  copper  or  brass  must  be 
strictly  avoided,  as  they  would  form  colored  alloys  with  the  alu- 
minium and  the  solder.  The  use  of  the  little  tools  of  aluminium 
is  an  art  which  the  workman  must  acquire  by  practice.  At  the 
moment  of  fusion  the  work  needs  the  application  of  friction,  as 
the  solder  suddenly  melts  very  completely.  In  soldering  it  is 
well  to  have  both  hands  free  and  to  use  only  the  foot  for  the 
blowing  apparatus." 

We  also  find  the  following  alloys  credited  to  Mourey  as  used 
by  him  for  soldering  aluminium,  probably  in  the  same  manner  as 
has  just  been  described  : — * 

Aluminium       .         .         .  .         .         .30  20 

Copper      .         .         .         .         .         .         .         .     20  15 

Zinc  ........     50  65 

Col.  Wm.  Frishmuthf  recommends  a  solder  containing : — 

Aluminium     .........     20 

Copper 10 

Zinc        .         .         .         .         .-."»...     30 

Tin ,         .         .         .60 

Silver .         .10 

Later,  Col.  FrishmuthJ  states  that  the  solder  just  given  is  used 
for  fine  ornamental  work,  while  for  lower-grade  work  he  uses  the 
following : — 

i.        n.         in. 

Sn  .         .         .        ^         .         .         .95         97         98-99 

Bi  .         .         .        .        .        .         .       5          3          2-1 

He  recommends  for  a  flux,  in  all  cases,  either  paraffin,  stearin, 
vaselin,  copaiva  balsam,  or  benzine.  In  the  solder  for  fine  wTork, 
if  aluminium  is  used  in  larger  quantity  than  recommended,  the 
solder  becomes  brittle. 

Schlosser§  recommends  two  solders  containing  aluminium  as 
especially  suitable  for  soldering  dental  work,  on  account  of  their 
resistance  to  chemical  action.  Copper  cannot  be  allowed  in  alloys 

*  Dingier,  166,  205.  f  Techniker,  vi.  249. 

J  Wagner's  Jahresb.,  1884.  §  Das  Lothen,  p.  103. 


362  ALUMINIUM. 

intended  for  this  use,  or  only  in  very  insignificant  quantity,  since 
it  is  so  easily  attacked  by  acid  food,  etc.  Since  these  two  alloys 
can  probably  be  used  also  for  aluminium  dental  work,  we  subjoin 
their  composition — 

Platinum-aluminium  solder.  Gold-aluminium  solder. 

Gold         ...     30  Gold        .         .         .50 

Platinum          .         .       1  Silver      ...     10 

Silver      .  .     20  Copper    .         .         .     10 

Aluminium      .         .  100  Aluminium     .         .     20 

M.  Bourbouze  states  that  the  difficulties  met  with  in  soldering 
aluminium  are  satisfactorily  overcome  by  the  following  process  : — 

*"  The  parts  to  be  united  are  subjected  to  the  ordinary  opera- 
tion of  tinning,  except  that,  in  place  of  pure  tin  an  alloy  of  tin 
and  zinc,  or,  better,  of  tin,  bismuth  and  aluminium  is  used. 
However,  preference  is  given  to  an  alloy  of  tin  and  aluminium, 
mixed  in  different  proportions  to  suit  the  work  put  on  the  joint. 
For  those  which  are  to  be  subsequently  worked,  an  alloy  of 
45  parts  tin  and  10  parts  aluminium  should  be  used.  This 
solder  is  malleable  enough  to  resist  hammering,  drawing,  or  turn- 
ing. Pieces  not  to  be  worked  after  soldering  may,  whatever  the 
metal  to  be  united  to  the  aluminium,  be  solidly  soldered  with  a 
tin  solder  containing  less  aluminium.  Neither  of  these  solders 
requires  any  preparation  of  the  pieces,  and  the  last  one  may  be 
applied  with  a  common  soldering-iron.  To  unite  other  metals  to 
aluminium  it  is  best  to  coat  the  part  with  pure  tin,  the  aluminium 
is  coated  with  one  of  the  above  alloys,  the  joint  closed  and 
finished  by  heating  in  the  usual  manner. 

O.  M.  Thowless  has  patented  the  following  solder  for  alu- 
minium, and  method  of  applying  it  :f  The  alloy  is  composed 
of— 

Tin 55  parts. 

Zinc 23      " 

Silver 5      " 

Aluminium  .         .         .         .         .         .  2      " 

The  silver  and  aluminium  are  first  melted  together,  the  tin 
added,  and  lastly  the  zinc.  The  metallic  surfaces  to  be  united 

*  Comptes  Rendue,  98,  1490. 

f  English  Patent,  10237,  Aug.  29,  1885. 


WORKING   IN    ALUMINIUM.  363 

are  immersed  in  dilute  caustic  alkali  or  a  cyanide  solution,  washed 
and  dried.  They  are  then  heated  over  a  spirit  lamp,  coated  with 
the  solder  and  clamped  together,  small  pieces  of  the  alloy  being 
placed  around  the  joints.  The  whole  is  then  heated  to  the  melt- 
ing point  of  the  solder  and  any  excess  of  it  removed.  No  flux 
is  used. 

J.  S.  Sellon  patents  the  following  method  :*  The  aluminium 
surfaces  are  cleaned  by  scraping  and  covered  with  a  layer  of 
paraffin  wax  as  a  flux.  They  are  then  coated  by  fusion  with  a 
layer  of  an  alloy  of  zinc,  tin  and  lead,  preferably  in  the  propor- 
tions 

Zinc          ..........     5 

Tin  i         .         .         .         .         .         .  "       .         .         .     2 

Lead .1 

The  metallic  surfaces  thus  prepared  are  soldered  together  in  the 
usual  way  with  any  good  solder. 

I  am  quite  aware  of  the  criticism  which  the  above  information 
about  aluminium  solders  will  meet, — that