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Issued July 17, 1908. 



Si U. S. DEPARTMENT OF AGRICULTURE, 



BUREAU OF ANIMAL INDUSTRY.— Bulletin 107. 

A. D. MELVIN, <Jhief op Bureau. 



IHb ANALYSIS OF COAL-TAR CREOSOTE 
AND CRESYLIC ACID SHEEP DIPS. 




BY 



ROBERT M. CHAPIN, 

Assistant Chemist, Biochemic Division. 



fornia 
mal 

■ty 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
19Q8. 



Issued July 17, 1908. 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ANIMAL INDUSTRY.— Bulletin 107. 

A. D. MELVIN, Chief of Bureau. 



THE ANALYSIS OF COAL-TAR CREOSOTE 
AND CRESYLIC ACID SHEEP DIPS. 



BY 



ROBERT M. CHAPIN, 

Assistant Chemist, Biochetnic Division. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE, 
1908. 



THE BUREAU OF ANIMAL INDUSTRY. 



Chief: A. D. Melvin. 

A.sniatant Chief: A. M. Farbinoton. 

Chief Clerk: E. B. Jones. 

Biochcmic Division: M. Dorset, chief; James A. Emery, assistant chief. 

Dairy Division: Ed. H. Webster, chief; C. B. Lane, assistant chief. 

Inspection Division: Kice P. Steddom, chief; Morris Wooden, R. A. Ramsay, 
and Albert E. Behnke, associate chiefs. 

Pathological Division: John R. Mohler, chief; Henry J. Washburn, assist- 
ant chief. 

Quarantine Division: Richard W. Hickman, chief. 

Division of Zoology: B. H. Ransom, chief. 

Experiment Station: E. C. Schroeder, superintendent ; W. E. Cotton, assistant. 

Animal Husbandman: George M. Rommel. 

Editor: James M. Pickens. 

BIOCHEMIC DIVISION. 

Chief: M. Dorset. 

Assistant chief: James A. Emery. 

Meat inspection laboratories: Central laboratory, T. M. Price In charge; R. H. 
Kerr, Philli) Castleman, E. H. Ingersoll, R. R. Henley, E. J. Ralph, J. N. Taylor, 
W. B. Meyer, H. I. Littlejohn, assistants. Chemists In branch laboratories: 
Ralph Hoagland, A. E. Graham, C. H. Swanger, A. H. Roop, W. B. Smith, 
E. A. Boyer, Clarence T. N. Marsh, W. P. Colvln, W. C. Powlck, J. B. Munroe. 

Hog cholera investigations: In charge of Chief of Division; C. N. McBryde, 
bacteriologist; W. B. Nlles, Inspector In charge of field experiments; H J. Shore, 
assistant bacteriologist. 

bacteriological investigations of meat food products: C. N. McBryde, bacteri- 
ologist in charge. 

Investigations of animal dips: Robert M. Chapin, In charge; A. V. Fuller, 
assistant. 

Investigations of disinfectants: Frank W. Tllley, bacteriologist. 

Preparation of tuberculin and mallein: In charge of Chief of Division; A. M. 
West and H. J. Shore, assistant bacteriologists; W. S. Stamper, H. S. McAuley, 
Roy E. Burnett, assistants. 



LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 

Bureau of Animal Industry, 

Washington, D. C, April 13, 1908. 

SiK : I have the honor to transmit herewith and to recommend for 
publication as a bulletin of this Bureau the accompanying manuscript 
entitled " The Analysis of Coal-tar Creosote and Cresylic Acid Sheep 
Dips," by Robert M. Chapin, assistant chemist in the Biochemic 
Division. 

The Department, in accordance with Bureau of Animal Industry 
Order 143, sanctions the use of certain classes of preparations for the 
official dipping of sheep and cattle. A large number of dips are 
manufactured and used throughout the country, and samples are con- 
stantly being submitted to the Department for the purpose of having 
their use permitted in official dipping, the analytical work as a basis 
for passing on them being performed in the Biochemic Division of 
this Bureau. 

This paper deals with methods of determining the various constit- 
uents of dips prepared from coal-tar derivatives. It has become of 
some importance to find methods of analysis which shall be sufficiently 
accurate and at the same time not make excessive demands upon the 
skill or time of the analyst, and the methods proposed in the paper 
appear to be comparatively simple and considerably more accurate 
than those heretofore employed. They should accordingly be useful 
to persons concerned in the examination and production of such dips, 
and are expected to assist manufacturers in meeting the Department's 
requirements. 

Respectfully, A. D. !Melvin, 

Chief of Bureau. 

Hon. James Wilson, 

Secretary of Agriculture. _ 



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CONTENTS. 



Page. 

Introductory 7 

Coal-tar creosote dips 7 

Current methods of analysis 8 

Criticism of methods 9 

Method of analysis adopted by the Bureau 10 

Determination of water 10 

Determination of soda and pyridin bases 11 

Determination of phenols 13 

Determination of rosin acids 17 

Determination of occasional ingredients 20 

Cresylic acid dips 21 

Method of analysis adopted by the Bureau 22 

Determination of water 22 

Determination of potash (or soda) and pyridin 22 

Determination of phenols 22 

Determination of rosin or fatty acids 22 

Analysis of coal-tar oils and commercial cresylic acid 24 

Calculation of proper dilution of dips 25 

Coal-tar creosote dips 25 

Cresylic acid dips 27 

Experimental work with methods of analysis 27 

Determination of phenols 27 

Tests with coal-tar creosote dips of known composition 30 

Test with cresylic acid dip of known composition 32 

Tests for nonvolatile acid bodies in coal-tar creosote and commercial 

cresylic acid 33 

Summary 35 



LLUSTRATION. 



Page. 
Figure 1. Tube for measuring phenols 16 



THE ANALYSIS OF COAL-TAR CREOSOTE AND CRESYLIC 
ACID SHEEP DIPS. 



INTRODUCTORY. 

The Department of Agriculture at present sanctions the use of 
properly constituted coal-tar creosote and cresylic acid preparations, 
commonly termed " dips." for the official dipping of sheep for the 
cure of scabies. The proprietor of each dip must, however, fulfill 
certain requirements in order that the use of his product may be 
permitted in official dipping, involving the submission of a sample 
to the Dei^artment for examination." The Biochemic Division of 
the Bureau of Animal Industiy has accordingly been obliged to 
examine a large number of these compounds and to confront the 
problem of finding analytical methods of considerable accuracy 
which would yet not make excessive demands upon the skill or time 
of the analyst. While these substances have, of coui'se, afforded 
a field for investigation by a number of different Avorkers. so far as 
known no other laboratory has been compelled to make their detailed 
examination such a matter of routine. Accordingly the methods 
here applied may be of interest to others who have occasion to 
examine these or similar compounds, as well as to manufacturers. 

COAL-TAR CREOSOTE DIPS. 

These dips are quite simply made by dissolving rosin in phenol- 
bearing coal-tar oils, adding an aqueous solution of caustic soda and 
applying a moderate degree of heat until saponification is complete. 
The undiluted dip should be a clear, uniform liquid, showing no 
separation of its constituents. When properly diluted with a con- 
siderable quantity of water there results a permanent, uniform emul- 
sion, from which, on standing, no oily layer or globules should 
separate either at top or bottom. 

The completed dip will contain, then, the following substances: 
(1) Coal-tar hydrocarbons, (2) phenols, (8) pyridin and other vola- 
tile bases contained in coal-tar oils, (4) rosin acids, (5) soda (XaoO), 
(G) water. In special cases certain other substances may be looked 
for. The rosin acids and soda will be present in approximatelj' 

" Hureau «)f Animal Industry Order 143. 



8 ANALYSIS OF COAL-TAR SHEEP DIPS. 

equivalent proportions in combination as a rosin soap. To the latter 
sul)stancv is clue the power of the dip to form a perfect emulsion 
when diluted with water. 

CURRENT METHODS OF ANALYSIS. 

Methods of analysis heretofore employed may [ye classified into 
(a) commercial and (b) scientific. 

The commercial methods aim at quick results and assume that the 
hydrocarbons antl })henols alone need be determined, since they are 
the essential Lnfjredients of the dip. A measured or weighed amount 
is shaken with acjueous sulphuric acid, the separated aqueous layer is 
run otf, and the residual oily portion is poured into a fractionating 
flask and distilled into a graduated cylinder until rosin begins to 
decompose, as shown by the character of the vapors and the distillate. 
The distillate will then supposedly contain all the phenols and all 
the coal-tar hydrocarbons except a slight amount remaining in the 
flask, which, however, is in a measure balanced by a small amount 
of rosin oil in the distillate. After taking the volume and specific 
gravity of the distillate in the cylinder, strong aqueous caustic soda 
is introduced ; the cylinder is then stoppered and thoroughly shaken. 
Phenols will be taken up by the caustic soda, and will be contained in 
the alkaline aqueous layer which separates after the cylinder has 
stood some time. The volume of hydrocarbons in the amount of dip 
taken may theji be read directly, and the volume of phenols may be 
obtained by difference or by noting the increase in volume of the soda 
solution. 

The process undoubtedly undergoes some modifications in the hands 
of different workers, but the foregoing is a general outlijie of a class 
of methods which are apparently used considerably by commercial 
chemists, judging from information which has come to the Biochemic 
Division from several different sources. 

The scientific methods follow in general the system given by 
Allen." Fifty grams of dip are shaken with ether and aqueous sul- 
phuric acid. Bases are removed in the aqueous layer, which is then 
treated with excess of sodium hydroxid, and the volatile bases are 
distilled off with steam and determined in the distillate by titration 
with standard acid and methyl orange. The ethereal portion is 
shaken with aqueous caustic soda, which removes phenols and rosin 
acids, leaving in ethereal solution In^drocarbons which are weighed 
after expulsion of ether. The alkaline aqueous solution of phenols 
and rosin acids is acidified with sulphuric acid, and the phenols are 
distilled over with steam and determined in the distillate by any suit- 
able method. The distillation flask containing the rosin acids is 

"Allen, A. H., C'omiuercial Organic Analysis, 3d ed., Vol. II, Pt. II, p. 262. 
lUOl. 



CRITICISM OF CURRENT METHODS OF ANALYSIS. 9 

cooled, the rosin acids are separated by ether and, after expulsion of 
ether, weighed. Soda is determined by ignition of a small portion 
of the dip in a crucible, either to sodium carbonate or, with addition 
of sulphuric acid, to sodium sulphate. 

CRITICISM OF METHODS. 

The commercial method of analysis, while rapid, contains some 
serious sources of error. Obviously a little of the phenols is lost in 
the acid aqueous extract. Moreover, practically all dips contain 
more or less voluminous insoluble carbonaceous matter, which con- 
duces to the formation of an emulsion at the junction of the two 
layers in the separating funnel. Loss of hydrocarbons and phenols 
results if this emulsion is run off, while if allowed to remain with 
the oily layer, water together with sulphur dioxid or hydrogen sul- 
phid will pass into the distillate, all of which tend to increase un- 
duly the volume of hydrocarbons and phenols when the latter are 
measured. It is also difficult to decide exactly when to stop distilla- 
tion, particularly in those dips containing oils of very high boiling 
point. In any case the distillate will contain some rosin oil, while 
some coal-tar oil will be left behind with the rosin, the relative 
amounts of which will vary according to the individual judgment of 
the analyst and will depend to a considerable extent upon the char- 
acter and proportions of rosin and coal-tar oil in the particular dip 
under examination. 

But the most serious source of error, and the one which by itself 
renders the method utterly untrustworthy, is the fact that undecom- 
posed rosin is distilled along with the hydrocarbons and phenols. 
This rosin, which in dips containing much oil of high boiling point 
may amount to several grams, is of course taken up by the aqueous 
caustic soda with which the distillate is shaken, and will conse- 
quently cause the amount of phenols to appear several per cent too 
high. Nor is the presence of rosin in the distillate due to carrying 
the distillation too far. To decide this point dips were distilled as 
described, and the distillate was collected in six to eight fractions. 
Each fraction was treated according to the scientific method for the 
separation of hydrocarbons, phenols, and rosin. The results showed 
that rosin began to come over soon after 200° C. had been reached, 
and continued to appear in increasing quantity, while the distillation 
of phenols is certainly not complete at 250° C. It appears, there- 
fore, utterly useless to attempt to develop any accurate method of 
analysis along these lines. 

The .scientific method, though far superior to the commercial in 
accuracy, possesses numy disadvantages. As is well known, hydro- 
carbons are considerably soluble in aqueous sodium resinate and 
sodium cresylate, while both of these latter salts, particularly cresy- 
42557—08 2 



10 ANALYSIS OF COAL-TAR SHEEP DIPS. 

lates, are readily hydrolyzed, and yield notable amounts of their 
acids to ether. Hence many extractions and reextractions are neces- 
sary to obtain anything like a complete separation of hydrocarbons 
from rosin and phenols, and the process requires much time and 
much ether. Moreover, it is often impossible to obtain a satisfactory 
result on weighing the hydrocarbons because their volatility renders 
it difficult to free them completely from ether and moisture without 
undue loss. Many dips contain a certain percentage of light oils, 
and obviously results may then be far from the truth. Petroleum 
ether, with the accompanied use of alcohol, offers no advantages in 
the operation of extraction, and renders the final weight of hydro- 
carbons still more uncertain. 

METHOnS OF ANALYSIS ADOPTED BY THE BUREAU. 

In deciding upon an official method of analysis it was desirable to 
adopt one that would not depend largely upon the individual judg- 
ment of the analyst, but would give definite and concordant results 
when the same sample was handled by different operators, and these 
results should closely approximate the truth. It is evident that the 
scientific method just referred to is far from satisfactory in this re- 
sjject. It is also evident that no method which involves separation 
of the hydrocarbons and the determination of their weight can yield 
results fret' from suspicion. For the other ingredients of these dips 
workable methods have been found which attain reasonable accuracy 
and give concordant results in the hands of any chemist of ordinary 
ability with a little practice, and which do not make excessive de- 
mands upon time nor require expensive chemicals. It has seemed 
best, therefore, to determine these other ingredients, to subtract the 
total of the percentages so obtained from 100, and to call the remain- 
der •' hydrocarbons.'' 

The following methods are accordingly those now employed in the 
laboratories of the Biochemic Division. The dip is well shaken be- 
fore weighing, and the latter operation is most conveniently per- 
formed by pouring into a beaker somewhat more than the amount 
needed, balancing on the scales, and pouring off the desired amount 
into the receptacle to l)e used in the analysis. 

DKTEBMINATION OF WATER. 

Fifty grams of dip is weighed into a 100 c. c. fractionating flask 
with a moderately high side tube, beyond the exit of which the neck 
should continue for not more than one inch, and the flask is con- 
nected with a small water-cooled condenser and carefully heated with 
a smoky flame until oils come over freely and carry no trace of water 
with them, but the distillation should not be unnecessarily continued. 



METHODS OF ANALYSIS ADOPTED BY THE BUREAU. 11 

The distillate is received in a properly graduated 25 c, c. cylinder, 
allowed some time to separate completely, and the volume of water 
read. The number of cubic centimeters of water multiplied by 2 
equals the percentage of water. Ordinarily the process offers no diffi- 
culties. A dip extremely high in rosin may bump and froth over, no 
matter how carefully heated. In such a case a larger flask is used, 
and the dip is diluted with about an equal volume of water-free min- 
eral or coal-tar oil. In case separation of the distillate is imperfect 
a small measured amount of strong XaCl solution is added from a 
jjipette, and the cylinder is nearly filled with benzol, shaken, and left 
at rest for some time. The volume of NaCl solution added is of 
course to be deducted when the reading is taken. 

DETERMINATION OF SOUA AND PYRIDIN BASES. 

The method, which is a novel combination and adaptation of Avell- 
known principles and processes, depends upon the fact that pyridin 
bases are alkaline toward method orange, but not toward phenolphtha- 
lein. A known weight of dip is shaken in a separatory funnel with 
ether and water to which a known amount of sulphuric acid has been 
added. Rosin soap is thus decomposed, and all bases contained in 
the dip will pass as sulphates into the lower acid aqueous layer which 
soon separates. The latter is quantitatively removed, and, ignoring 
acid salts for the sake of simplicity, will contain the substances — 

(a) (b) (c) 

Stage I. Xa,80,. H,80,. (C,H,X),H,80,. 

If methyl orange is now added and the solution titrated to neu- 
trality with standard caustic soda the result will be — 

(a) (b) (c) 

Stage 11. Na,SO,. Na^SO,. (C5H5N),H,SO,. 

If next phenolphthalein is added and titration with standard 
caustic soda continued until the solution is neutral to that indicator, 
the final condition of the solution will be — 

(a) (b) (c) 

Stage III. Xa.SO,. Xa.SO,. Na.SO,. C,H,X. 

Obviously the amount of caustic soda required to change the solu- 
tion from Stage II to Stage III will be a measure of the amount of 
pyridin present, while if the amount of caustic soda added in the 
whole titration is subtracted from the e<iuivalent in soda of the 
sulphuric acid originally introduced the remainder will equal the 
amount of soda in the dip. Briefly, the amount of soda equivalent to 
H2SO4 (c) measures pyridin; soda equivalent to H.^SO^ [(a-j-b-f-c) — 



12 ANALYSIS OF COAL-TAR SHEEP DIPS. 

(b-|-o) ] is the soda of the dip. The process is executed in the follow- 
ing manner: 

Ten trranis of dip is weighed into a 200 c. c. short-stemmed separat- 
inir funnel. 50 c. c. ether added, exactly 30 c. c. of N/2 H.SOj run 
in from a burette and the funnel shaken. The lower aqueous layer, 
which now contains the bases, is drawn off completely, together with 
any insoluble carbonaceous matter which may appear at the junction 
of the two layei-s. No harm is done if a small amount of the ethereal 
layer accompanies the insoluble matter in the separation. The 
ethereal solution remaining in the funnel is next washed four times 
with water, using about 20 c. c. each time. In the first of these wash- 
ings the funnel should not-l)e shaken, but the water should be drawn 
off at once, the object being to wash out the stem of the funnel and so 
avoid loss of a little acid therein contained. 

All tlie aqueous extracts are united and heated on the steam bath 
for expulsion of ether. The liquid is then passed through a wet filter 
into a 300 c. c. flask, the filter washed with hot water, the flask cooled, 
filled to the mark, and the contents exactly divided between two uni- 
form titrating flasks of about 300 c. c. capacity. To one of these 
portions add methyl orange, then N/2 NaOPI till the red tint just 
disappears, as nearly as can l^e determined by comparison with the 
second portion. Then add one-tenth or two-tenths of a cubic centime- 
ter more of N/2 NaOH to make sure that neutrality has been reached, 
though much excess must be avoided, else the separation of higher 
pyridin bases will render the solution turbid. 

This first titration is not quantitative, but merely to aflFord a 
.standard of comparison, b}' the aid of which the second portion is 
quantitativeh' titrated to exact neutrality, after the addition of an 
equal amount of methyl orange. The number of cubic centimeters of 
N/2 NaOH used is noted, phenolphthalein added, and the titration 
continued to the end point of that indicator. To obtain the per cent 
of NaoO in the dip, subtract the total number of cubic centimeters 
of N/2 NaOH used in the whole titration of the second portion from 
15, and multiply the remainder by 0.31. To obtain the per cent of 
volatile bases reckoned as pyridin, multiply the number of cubic 
centimeters of N/2 NaOH used between the end points of methyl 
orange and phenolphthalein by 0.79. The only difficulty in the 
method is the determination of the point of neutrality toward methyl 
orange, but a proper use of the standard of comparison will satis- 
factoril}'^ overcome this." 

" Recent work has indicated that the coloring matters which tend to interfere 
with the accurate observation of the end ix)int with methyl orange may be 
almost entirely removed from the solution by the use of animal charcoal. 
Powdereil animal charcoal is digested on the steam bath with dilute hydro- 
chloric acid in sufficient quantity to decompose and dissolve all carbonates and 



THE DETERMINATION OF PHENOLS. 13 

Results obtained for pyridin run between 0.05 and 0.1 per cent 
higher than by Allen's method. 

DETERMINATION OF PHENOLS. 

The regulations of the Department of Agriculture " include under 
the designations " phenols," " cresols," and " cresylic acid " those 
phenols whose boiling points range between 185° C. and 250° C. 
Benzophenol, or pure carbolic acid, having a boiling point of 182° C., 
is accordingly excluded, the reason for such distinction being that 
it is considerably more toxic in its effect upon animals than the 
phenols of higher boiling points. ' As a matter of fact the compara- 
tively high market value of pure carbolic acid as a separate product 
renders unlikely the presence of more than traces of it in such com- 
pounds. It is well known that the so-called crude carbolic acid of 
commerce consists almost entirely of higher phenols. 

There are but few methods for determining phenols which have 
received at all extended application. Of these the only direct acidi- 
metric method, that of Bader,^ is applicable to benzophenol alone, 
and hence is of no value in the present case. A direct gravimetric 
deteiTnination, in addition to its inherent sources of error, demands 
a complete separation of hydrocarbons from the phenols. So also 
does any volumetric method based upon the reaction between phenols 
and bromin or iodin. This separation of hydrocarbons from phenols, 
as noted under the description of the scientific method of analysis, 
is tedious and uncertain, and is to be avoided if in any way possible. 

There will appear, then, to be two methods practically applicable 
in the present case — the method of Schryver,*" by which the phenols 
are acted upon in benzol solution by sodamid and the evolved am- 
monia titrated, and the German method of measuring the increase in 



phosphates present, theu washed with hot water until the wash water is free 
from chlorids, and tinallj- dried and powdered. 

In the course of an analysis, after the tiasli containing the acid extract from 
the dip has been heated upon the steam batli until ether has l>een completely 
expelled, 1 to 1.5 grams of the i)urified animal charcoal is added, and the llask, 
frequently shaken, is left upon the steam bath for 30 to GO minutes. The 
contents are then filtered, washed, and titrated as usual. After pr<)|)er treat- 
ment with animal charcoal in this manner the solution will be a pale green in 
color, possessing none of the muddy yellow tint which tends to obscure the end 
point with methyl orange. 

Expefiments have thus far failetl to show that any inaccuracy is intrmluced 
into the u)ethod by the use of animal charcoal in the manner described. 

"Bureau of Animal Industry Order 143, i). is. 

'Zeitschrift fiir Analytisclie Cliemie, jahrg. :n, p. .".S-«R>. Wiesbaden, 1892. 

'^ Jotirnal of the S<x'iety of Chemical Industry, vol. 18, No. G, [k i>')'.i-'trA>. I>on- 
dou, June 30, 1899. 



14 ANALYSIS OF COAL-TAR SHEEP DIPS. 

volume of a caustic soda solution when the phenols are absorbed by it. 
In either case the phenols may be separated from interfering sub- 
stances by steam distillation of the acidified dip. Schryver's method 
is essentially a direct determination of the amount of phenol hydroxyl 
j)resent, and the actual weight must be obtained through a knowledge 
of the mean molecular weight derived from other considerations. 
The German method, on the other hand, is a measure of the volume 
of the i)henols when in solution under certain conditions, and the cor- 
responding weight can be obtained only by the employment of an em- 
pirical factor or coefficient found to hold true for that particular 
kind of phenol under those particular conditions. Since in both 
methods a certain factor must be somewhat arbitrarily adopted by 
which the numbers directly obtained are to be multiplied in order to 
obtain the weight of phenols present, and since the possible error 
thereby involved appears of about the same magnitude in both, that 
one will naturally be chosen which is easiest of execution, in which 
respect Schr^'ver's method is at a decided disadvantage. 

The methods of procedure which considerable experimental work 
has shown to be satisfactory is as follows : 

F'ifty grams of dip is weighed into a .500 c. c. round-bottomed flask, 
20 c. c. of 1 : 3 HoSO^ is added, and the phenols are distilled off with 
steam. The flask will require no heating if a rapid current of steam 
is passed into it, but may with advantage be packed in cotton or felt. 
Obviously the apparatus must be so set up and the distillation so 
conducted that particles of rosin may not be mechanicalh' carried 
over by the current of steam. Toward the end of the distillation 
any naphthalene in the condenser is melted out bj' shutting off the 
water for a few minutes, or if separated earlier in sufficient quantity 
to threaten stoppage of the condenser tube, distillation is interrupted 
while hot water is run through the condenser. The distillate is re- 
ceived in a liter flask approximately marked for each 100 c. c. capacity 
and joined to the condenser by a cork which is pierced by a small 
glass tube connected to a small U tube containing a little dilute 
caustic soda. The latter acts as a trap to prevent any loss of the dis- 
tilled phenols. Distillation is continued until 1 or 2 c. c. collected in 
a test tul)e gives no reaction with any appropriate reagent for phe- 
nols, such as ferric chlorid. A volume of 800 c. c. is ample in nearly 
all cases. 

A supply of benzol should be prepared by shaking a good grade of 
lienzol with dilute sulphuric acid, then with dilute caustic soda two 
or three times, and then passing through a dry filter. A small wash 
bottle containing some of this benzol will be found very useful for 
rinsing the necks of separatory funnels, etc. Of this purified benzol 
150 c. c. is measured out conveniently at hand, the contents of 



THE DETERMINATION OF PHENOLS. 15 

the U tube and 5 c. c. of 1 : 1 HoSO^ are added to the distillate, 
and the latter is shaken up and poured into a separatory funnel of 
1,500 c. c. capacity, the flask being rinsed out with successive portions 
of the 150 c. c. benzol. When all is in the funnel 25 grams of clean 
sodium chlorid is added for each 100 c. c. of distillate, and the funnel 
is well shaken for five minutes and left at rest one-half hour. The 
aqueous layer is then run off slowly and completely, the funnel being 
allowed to stand until there is no further separation. The benzol 
solution of phenols and hydrocarbons is transferred to a 500 c. c. 
Erlenmeyer flask, while the aqueous portion is poured back into the 
separating funnel and extracted twice more in the same way, 100 c. c. 
of benzol being used each time. The funnel should always be gently 
handled after the aqueous portion has been drawn off, to prevent any 
impurities from the sodium chlorid which have deposited upon its 
sides from becoming mixed with the benzol solution. The three ben- 
zol extracts are united in the Erlenmeyer flask, 15 c. c. of pure caustic 
soda solution, 1 : 2, is added, and the contents of the flask are subjected 
to a rotatory motion for some time in order that the phenols may be 
taken up by the caustic soda as completely as possible. 

After the addition of a few grains of sand the flask is immersed in 
a water bath, connected to a condenser, and all but 40 to 50 c. c. of the 
benzol distilled off. With the aid of a wash bottle containing water 
and provided with a fine jet, only a small portion of water being used 
at a time, the contents of the flask are next carefully washed into a 
150 c. c. separatory funnel. With proper manipulation the flask 
should be completely washed when the volume of aqueous portion in 
the separatory funnel amounts to not more than 50 c. c. Ten cubic 
centimeters of strong sulphuric acid (100 c. c. pure concentrated 
HgSO^ to 120 c. c. water) is next slowly introduced with gentle rota- 
tion of the funnel, the addition of acid being interrupted and the 
funnel cooled whenever it becomes unpleasantly warm to the hand. 
Two or three drops of methyl orange are now added; and if on mix- 
ing the contents of the funnel the lower layer does not acquire a pink 
color, the addition of acid is continued until acidity is assured. Suffi- 
cient benzol is then added to make the two layers in the funnel ap- 
proximately equal in volume, the funnel is thoroughly shaken and, 
with loosened stopper, left at rest for two hours. After that time 
the aqueous layer is slowly and completely run out, the analyst mak- 
ing sure that on longer standing no more will drain down from the 
sides of the funnel. The benzol solution of phenols is then ready to be 
transferred to the measuring tube. 

The measuring tube consists of a glass-stoppered pear-shaped bulb 
of about 100 c. c. capacity, joined at its tapering end to a tube about 
1 foot long and of a capacity of 25 to 30 c. c. This tube is accurately 



16 



ANALYSIS OF COAL-TAR SHEEP DIPS. 



gradiia 




ted to contain 25 c. c. at 20° C. in divisions of one-tenth c. c. 
(See fig. 1.) 

The apparatus is cleaned thoroughly with 
soap powder and hot water, and dried, best 
spontaneously, though alcohol and ether may 
be used if pure. Perfect cleanliness is essen- 
tial to insure a proj^erly shaped meniscus. 
Between 15 and 16 c. c. of caustic soda solu- 
tion, 1:3, is brought into the tube with a 
l)ipette. The caustic soda should not be al- 
h>wed to come in contact with the interior 
of the bulb or the upper part of the tube. 
After a few moments about 1 c. c. of benzol 
is added, and after waiting a little the 
height to the top of the now almost flat 
meniscus is noted. The benzol solution of 
phenols is next transferred from the separa- 
tory funnel to the tube, care being used to 
avoid mixing with the soda ; the separatory 
funnel is washed out with a little benzol, 
which is also transferred to the tube, and 
the height of the meniscus is again noted. 
The latter may often be obtained more accu- 
rately at this point. The tube is then stop- 
pered, vigorously shaken for three minutes, 
and set aside for at least three hours. An oc- 
casional rapid rotation of the tube between 
the palms of the hands will insure a com- 
plete separation of the layers. Each cubic 
centimeter increase in volume of the caustic 
soda solution may be taken to represent one 
gram of phenols. All readings of the tube 
should be taken at the top of the meniscus 
and at a temperature as near 20° C. as prac- 
ticable. 

This method of treating the distilled phe- 
nols is essentially that of Spalteholz," 
though the details of its execution were not 
imparted in the original communication and 
had to be worked out independently. A 
discussion of the reasons for the different 
steps of the foregoing process will be entered 
into in a later section which deals with the 
experimental work done (see page 27). 



_25 



E2^ 



\22 



122 



EZl 



>Vsr~!?' 



yy 



Fig. 1.— Tube for measuring 
phenols. 



« Cheuiiker-Zeitiing. jahrg. 22, no, 8, pp. 58-59, Ciithen. Jan. 26, 1898. 



THE DETEEMINATION OF ROSIN ACIDS. 17 

From certain experiments it seems possible that a continuous ex- 
traction apparatus may be successfully employed to extract phenols 
from the aqueous distillate of the dip, using benzol as the solvent, 
and introducing caustic soda solution into the distillation flask of the 
apparatus at the beginning of the operation to retain the extracted 
phenols. A'^lien the extraction is completed the small Jlask of the ap- 
paratus will contain all the phenols, dissolved in a limited amount of 
caustic soda solution and overlaid by about 50 c. c. of benzol. The 
contents of the flask may then be brought readih^ and completely into 
a separatory funnel and acidified in the usual manner. Certain exi- 
gencies of the work in this laboratory have rendered somewhat incon- 
venient at the present time a practical test of this method of pro- 
cedure in the routine examination of dips submitted for analysis. 

DETERMINATION OF ROSIN ACIDS, 

Resins in general have been shown to contain at least three differ- 
ent classes of bodies:" (1) resin acids or anhydrids, (2) esters of 
these or similar acids, (3) indifferent neutral bodies, perhaps hydro- 
carbons. Common rosin, or colophony, contains, according to Allen,'' 
between 83.4 and 93.8 per cent of free rosin acids or anhydrids. The 
remaining G to 17 per cent consists of neutral bodies, soluble in ether 
and not extracted from ethereal solution by aqueous caustic soda, and 
accordingly there would seem to be no practicable means of distin- 
guishing and separating them from the coal-tar hydrocarbons of the 
dip. Apparently, then, the analyst must be content with a determina- 
tion of the amount of rosin acids present, which will represent about 
nine-tenths of the amount of rosin actually used in manufacturing the 
dip. Either a gravimetric or a volumetric method may be employed. 

Owing to the degree of uncertainty attached to the exact combining 
equivalent of the rosin acids in each particular dip, the gravimetric 
method has an indubitable advantage in point of accuracy when 
properly carried out. But as a matter of fact the combining equiva- 
lents of a considerable number of rosin acids obtained from different 
dips in the gravimetric way in the course of anahsis have been found 
to vary very little, not enough in any case to cause a possible error of 
half a per cent in the analysis of a dip of ordinar}' constitution. 
Moreover, in view of the difficulty of completeh' separating hydro- 
carbons from rosin acids, as is necessary in the gravimetric method, 
it is probable that the ordinary analyst without considerable practice 
in this particular operation will obtain quite as accurate results by 
the volumetric method as by the gravimetric. Accordingly the 

,. . . * 

"Allen, A. H., Commercial Organic Analysis, 3<1 e«l, rev., Vol. II, Pt. Ill, p. 
141. 1907. 
Md., p. 160. 

42557—08 3 



18 ANALYSIS OF COAL-TAR SHEEP DIPS. 

volumetric method would seem to recommend itself for use in ordi- 
nary routine work on account of its greater rapidity, simplicity, and 
probable equal accuracy under ordinary conditions, while the gravi- 
metric method may l)e reserved for dips extremely high in rosin or for 
a confirmatory method in special cases. 

For the determination of rosin acids by either method it is most 
advantageous to make use of the residue left in the distillation flask 
after the determination of phenols. From this residue all phenols 
and a large part of the hydrocarbons have been removed, hence the 
necessary extraction by ether is expedited. After cooling, the acjue- 
ous portion of the contents of the flask is poured into a separatory 
funnel, with as little rosin as possible, and extracted Avith ether. 
The acjueous portion is run otf and discarded, the residue in the flask 
is completely dissolved and brought into the funnel with ether, 40 
to 50 c. c. of water is added, and the funnel well shaken. The pres- 
ence of insoluble carbonaceous matter will usually cause a persistent 
emulsion at the junction of the two la3'ers, which may, in fact, en- 
tirely fill the lower part of the funnel. 

This is wholly run oft* into a 300 c. c. Erlenmeyer flask and the 
ethereal solution well shaken again with successive portions of water, 
the water being run off each time to the clear ethereal solution, until 
the carbonaceous matter is wholly removed and separation takes 
place in the funnel quickly and cleanly. These wash waters are all 
received in the flask containing the first separated emulsion, and 
this is heated upon the steam bath until ether is expelled. The con- 
tents are then brought more or less completely upon a Avet filter and 
washed with hot water. At this point the methods diverge. 

Grarimetric method. — In case the gravimetric method is to be 
employed, after a brief washing of the insoluble carbonaceous residue 
with hot water both flask and filter are well drained. Both are then 
washed, first with a little absolute alcohol to remove water, then thor- 
oughly with ether until all rosin is dissolved and the filtrate comes 
through colorless. 

The united ethereal solution of hydrocarbons and rosin is now 
thoroughly shaken with about -40 c. c. of 15 per cent caustic soda. 
On separation there will be three layers. The lowest one usually 
contains very little rosin soap, and consequently holds but a small 
amount of hydrocarbons. It is best run off and washed separately 
with ether. One washing will usually free it completely from 
hydrocarbons. 

After the first layer has been thus removed, about 50 c. c. of water 
is added to the funnel and the latter is well shaken. The lower layer 
of rosin soap is run oft" and followed by 5 to 10 c. c. of water without 
shaking, the funnel l)eing given only a gentle rotatory motion. The 
remaining ether solution of hydrocarbons is Avashed twice Avith 20 



THE DETERMINATION OF BOSIN ACIDS. 19 

to 25 c. c. of about 4 per cent caustic soda solution, each washing 
being followed by a little water as before described. These two 
washings with dilute caustic soda are kept apart and not added to 
the main solution of rosin soap. 

The main solution of rosin soap is now washed in a separatory fun- 
nel with successive portions of ether, followed through each time by 
5 c. c. of water, as at first, until the ether is left nearly colorless. The 
ether extracts are shaken through in their order with the two wash- 
ings of dilute caustic soda already used, and a third if needed, each 
being followed with a few cubic centimeters of water. 

All the aqueous extracts are united in a porcelain dish or casserole, 
which should be not more than half filled by them, and are evapo- 
rated on the steam bath until ether is dissipated and the volume re- 
duced to a convenient amount. The contents of the dish are then 
transferred to a separatory funnel with the aid of a spatula and hot 
water; strong sulphuric acid is added to decompose all rosin soap, 
and after complete cooling the rosin acids are extracted by ether and 
washed with water till free from sulphuric acid. The ethereal solu- 
tion is brought into a weighed Erlenmeyer flask with a few grains of 
.>5and, the ether is distilled off, and the flask is heated in an oven at 
110° C. until the absence of frothing on rotation shows elimination 
of water; it is then cooled and weighed. 

Vohimefric method. — As alread}' noted, the volumetric method 
proceeds identically with the gravimetric to the point where carbona- 
ceous matter is brought upon the filter and washed with hot water. 
The washing in this case must be continued until the wash water 
comes through entirely free from acid reaction. The main ethereal 
solution has meanwhile been brought into a flask and the ether dis- 
tilled off. The filter funnel is set in the neck of this flask, and the 
carbonaceous matter is washed with hot alcohol previously rendered 
neutral to phenolphthalein, until freed from rosin. The alcoholic 
solution of rosin is brought into a graduated flask, and an aliquot 
part, usually one-fourth, taken for titration with half-normal caustic 
soda. The titration is conveniently carried out in a 200 c. c. Erlen- 
meyer flask in a volume of 100 to 125 c. c, the portion taken being 
diluted with neutralized alcohol to that amount. 

Owing to the very dark color of the liquid an external indicator is 
necessary. For this purpose alkali blue is best adapted. A few droj)s 
of a strong alcoholic stock solution are added to 25 or 30 c. c. of 
alcohol, which is then carefully neutralized with tenth-normal caustic 
soda. Enough alkali blue should be added to produce a deep color, 
almost a cherry, wlien neutralized, with no trace of violet. This 
dilute indicator should be freshly prepared. A supply of small test 
tubes 8 to 10 millimeters in diameter and GO to 80 millimeters long 
should be at hand, cleaned and dried. When a test of the progress 



20 ANALYSIS OF COAL-TAR SHEEP DIPS. 

of the titration is to be made about ^ c. c. of prepared indicator is 
poured into one of these test tubes, and to this is added a drop of the 
liquid under titration. If a violet color appears, the solution still 
contains free rosin acid, and more N/2 XaOH must be added and the 
solution again tested with a fresh tube of indicator. If the indicator 
does not show a violet color upon the addition of one drop of the 
li<iuid under titration, addition of the latter is continued drop by 
drop until an amount has been added approximately equal in volume 
to the amount of indicator originally in the tul)e. i. e., \ c. c. The 
continued absence of a violet color after the addition of this amount 
indicates that the solution is either neutral or alkaline. The end of 
the titration then is reached when a greenish or violet tint just fails 
to appear. A fresh tube of indicator must be used for each test. It 
is best to proceed by running in 12 to 15 c. c. of half-normal caustic 
soda at once, testing and continuing addition if necessary', a cubic 
centimeter at a time, until the indicator shows alkalinity, then run- 
ning back with half-normal hydrochloric acid, using perhaps 0.4 c. c. 
at a time till acidit)" is shown, and now working carefully with half- 
normal caustic soda to exact neutrality. One cubic centimeter of 
half-normal caustic soda is considered to be equivalent to 0.162 gram 
of rosin acids. 

Phenolphthalein may also be used as an indicator in a similar way, 
bv preparing an alcoholic solution of quite a deep rose tint. The 
end point of the titration will then be reached when the indicator, 
used in the same way as alkali blue, is no longer bleached by the addi- 
tion of the liquid under titration. The color change is not so marked 
as in the case of alkali blue, and consequently the end point is not so 
sharp, though almost equally good results may be obtained with a 
little care and practice. 

All alcoholic solutions should be kept from contact with air as far 
as possible to prevent absorption of carbon dioxid. 

DETERMINATION OF OCCASIONAL INGREDIENTS. 

Liffht oils. — The presence of light oils will usually be indicated by 
the relative proportions of oil and water which come over in the early 
stages of the process of distilling the dip for the determination of 
water. The odor of the distillate should be noted at this point, to 
identify if possible the nature of the light oils present. If more 
information is desired, about 150 grams of dip is thoroughly shaken 
with 20 to 25 c. c. of 1 : 3 sulphuric acid, allowed some hours to sepa- 
rate, and a weight of oils, etc., equivalent to 100 grams of dip — i. e., a 
weight in grams equal to the sum of the percentages of hydrocarbons, 
phenols, and rosin — is distilled from an Engel flask fitted with a 
thermometer until the temperature reaches 180° C. The distillate 
is measured and further examined in any way desired. 



ANALYSIS OF CRESYLIC ACID DIPS. 21 

Naphthalene. — Too large a proportion of naphthalene or other solid 
hydrocarbons is undesirable on account of the liability of these bodies 
to separate from the dip in freezing weather and remain for a long 
time as an undissolved sediment. For an approximate determination 
of the amount of solid hydrocarbons present 50 grams of dip is acidi- 
fied with a little concentrated hydrochloric acid, 100 c. c. alcohol added, 
and the containing vessel immersed in a freezing mixture for two 
hours, with occasional stirring. The separated hydrocarbons are 
then filtered off on a Buchner funnel or plate, washed somewhat with 
chilled alcohol, well drained, and pressed out in a letterpress between 
several thicknesses of filter paper. The mass may then be weighed 
and subjected to any further examination desired. A more practi- 
cal test is to subject a portion of the dip itself to a temperature of 
0° C. for about three hours, with occasional shaking or stirring. It 
should remain perfectly clear and liquid and show no separation of 
solid matter. 

Foreign oils and creosotes. — By the regulations of the Secretary of 
Agriculture" the degree of dilution which may be accorded to a 
coal-tar creosote dip is explicitly made to depend upon the percent- 
ages of coal-tar oils and cresylic acid contained in the dip. Accord- 
ingly in the standardization of dips for official use, within the scope 
of the regulations, petroleum oil, rosin oil, or creosotes of other origin 
than coal-tar must be regarded as extraneous substances. Investiga- 
tions are now in progress to find satisfactory methods for detecting 
and estimating these substances when present in dips. At the present 
time, however, this line of work has not reached a point of develop- 
ment which warrants the publication of any results. 

CRESYLIC ACID DIPS. 

Cresylic acid or cresol dips in composition approximate more or less 
closely the " liquor cresolis compositus " of the United States Pharma- 
copoeia, eighth revision, 1905, being made from a potash-linseed oil 
soap and cresylic acid comparatively free from hydrocarbons. A 
properly prepared dip of this character should upon dilution in 100 
parts of distilled water yield a practically water-clear solution, show- 
ing absence of any notable amount of hydrocarbons or unsaponified 
oil. On dilution, however, with hard water there will naturally be 
sf>me turbidity, caused by the precipitation of soap. A portion of the 
dip when treated with successive small portions of water should show 
itself miscible in all proportions. At no stage hhould there l)e any 
notable turbidity or separation of heavy oily globules of cresylic acid 
due to absence of sufficient soap. 

<" Bureau of Aulnial Imlustry OrcU'r 14.'5, p. 18. 



22 ANALYSIS OP COAL-TAR SHEEP DIPS. 

METHODS or ANALYSIS AIX)PTED BY THE BUREAU. 

The methods of analysis adopted are essentially the same as for 
coal-tar tivosote dips, modified in details to suit the somewhat dif- 
ferent composition of the substances. 

UETEBMINATION OF WATER. 

The distillate must always be received in a stoppered cylinder and 
treated with benzol and sodium chlorid solution as described. The 
results will be about 0.5 per cent too low. The addition of toluene or 
a similar hydro<'arbon to the dip before distillation might possibly 
improve the results. 

DICTEBMINATION OF POTASH (OB SODA) AND PYBIDIN. 

A preliminary test is here necessary to determine whether potash or 
.soda is the alkali present. The test may be conveniently made by 
shaking about 10 grams of dip with ether and a little dilute hydro- 
chloric acid, drawing off the aqueous layer, and applying the flame 
test with a platinum wire, supplementing this with any other con- 
firmatory test necessary or desirable. If potash is found to be the 
alkali present the factor 0.471 must be used in place of the factor 0.31 
employed in the case of soda. 

DETERMINATION OF PHENOLS. 

Since the percentage of phenols will here he much higher than in 
coal-tar creosote dips, a smaller amount of dip must be taken for 
analysis, usually 15 to 20 grams. The amount should be as large as 
possible, in order that the greatest quantity of phenols within the 
capacity of the tube may l)e brought to measurement. A new oppor- 
tunity for error is here afforded. Linseed oil possesses a low Reichert- 
Meissl number, 00 to 1.43." This means that a small amount of vola- 
tile fatty acid will accompany the phenols through the stages of the 
process and tend to cause too high results. To determine the possi- 
ble amount of this error 25 grams of linseed oil was saponified, then 
acidified, and distilled with steam until 800 c. c. had been collected. 
The distillate was treated by the regular method and an increase in 
volume between 0.02 and 0.07 c. c. observed. In view of the fact that 
this (juantity of soap is four or five times as much as would be present 
in an ordinary analysis, the error which is likely to arise from this 
source would apjjear negligible. 

DETEBMINATION OF ROSIN OR FATTY ACIDS. 

The odor of the dip itself, and more especially the character of the 
residue left in the flask after the distillation of phenols, will inform 

* Hopkins's Oil Chemists' Handbook, page 38. 



DETERMINATION OF ROSIN IN CRESYLIC ACID DIPS. 23 

the analyst whether rosin or fatty acids are to be determined. Rosin 
will collect in a solid, hard button at the bottom, while fatty acids 
will form a liquid oily layer floating upon the surface of the aqueous 
contents. In either case the whole is extracted with ether, washed 
Avith water, and, after evaporation of ether, dissolved in neutralized 
alcohol and titrated with half-normal caustic soda. One cubic cen- 
timeter of half-normal soda will represent 0.138 gram fatty acid 
anhydrids" and 0.015344 gram glycerin. Cresol dips containing 
rosin soap are not at present permitted in official dipping. 

Such a detailed analysis of a cresol dip would appear, however, 
seldom necessary. Phenols must of course be determined as accu- 
rately as possible. An examination of the odor and appearance of 
the residue left in the flask after distillation of phenols will indicate 
the character of the soap emploj'ed. If, then, the behavior of the dip 
upon dilution is satisfactory (page 21) and indicates the presence of 
sufficient soap, the only remaining question is whether there may be 
an unnecessary and possibly harmful amount of alkali present. In 
the presence of the large amount of cresylic acid contained in these 
dips there can be, strictly speaking, no " free alkali." The ideal 
cresol dip will, however, unquestionably contain no alkali above that 
necessary to obtain complete saponification of the linseed oil. An 
excess of alkali can be of no possible benefit and might conceivably be 
undesirable for several reasons. A useful test for the presence of 
such an excess of alkali is that of Kelhofer.^ 

Ten grams of dip is thoroughly shaken in a small separatory funnel 
with 50 c, c. of a saturated solution of XaCl. After complete sepa- 
ration has taken place the lower aqueous layer is removed, diluted 
with an equal volume of water, and a few drops of phenolphthalein 
added. If the dip has been made from a perfectly neutral linseed- 
oil soap, there will appear at most but a slight reddening of the solu- 
tion, which vanishes upon the addition of a drop of half-normal 
acid. If more acid is required to remove the pink color, the pres- 
ence of an excess of alkali is indicated. The test can not be made 
quantitative, for experiments have shown that only a part of the 
excess of alkali actually present is accounted for in this way, the 
remainder probably being thrown up in the form of alkali cresylate 
into the upper layer with the soap. It would seem, then, reasonable 
to demand that no dip treated as described should require more than 
a very few tenths of a cubic centimeter of half-normal acid to remove 
the pink color imparted by phenolphthalein to the sodium chlorid 
extract. 

<* I^vvkowitscb, J., Chemical Technology and Analysis of Oils, Fats, and 
Waxes, ;id ed., Vol. I, p. '.iM. KMM. 

'I Schweizerische Wochenschrlft fiir Cheniio nnd riiarniazir, jalirj?. 4(1, No. 2, 
pp. ir>-20. Znrich, Jan. 11, 1!IU8. 



24 ANALYSIS OF COAL-TAR SHEEP DTPS. 

Duyk " proposes a method for the determination of soap in cresol 
dips, according to which the soap is separated by shaking the dip 
with a strong sugar sohition. The latter dissolves all the soap, which 
may be recovered by salting out with NaCl, and purified, if desired, 
by solution in alcohol. The method has not been tried in this 
laboratory. 

ANALYSIS OF COAL-TAR OILS AND COMMERCIAL CRESYLIC ACID. 

Obviously it is impossible for a numufacturer to produce a dip of 
constant composition closely adhering to the standard he has set for 
himself in his original sample submitted to the Department of Agri- 
culture for examination unless he knows exactly what goes into each 
lot of dip his factory turns out. The composition of coal-tar oils is 
subject to considerable variation ; consequently it is absolutely neces- 
sary for any manufacturer who wishes to secure and retain permis- 
sion for the use of his dip in official dipping to have at his disposal 
some means of accurately analyzing each lot of coal-tar oils he re- 
ceives. He may then blend his oils, or his oils and cresylic acid, in 
such proportions as always to preserve uniform the composition of 
his dip. 

The coal-tar oils to be used for dips nnist be examined for water, 
pyridin bases, and phenols. 

Water will be determined exactly as in dips (page 10). 

Pyridin bases will be determined exactly as in dips (page 11), but 
if the oils are old and highly colored it may prove advantageous to 
use 5 grams instead of 10. 

The hope was entertained that phenols in coal-tar oils and cresylic 
acid might be readily and accurately estimated by dissolving a 
weighed amount in benzol, shaking with acidified aqueous sodium 
sulphate to remove water, and then shaking the separated benzol 
solution in the measuring tube with caustic soda; in short, by repeat- 
ing exactly the last two steps of the method employed for phenols in 
dips. In fact, the latter was adopted for dips with considerable 
added satisfaction because it seemed to promise an easy solution of 
one of the most troublesome problems of dip making by affording 
such a simple means for valuing coal-tar oils, requiring no special 
technical training for its execution, and yet being a method strictly 
parallel in all respects to the method employed in analyzing the com- 
pleted dip. 

This hope was not realized, for it was found that some samples 
at any rate of creosote oils and of cresylic acid contain small amounts 
of acid bodies of some description, possibly phenoloids, possibly of a 
resinous nature, which are taken up by caustic soda, increasing its 

oAunales de Clilmie Analytique, 1. 12, No. 9, pp. 345-346. Paris, Sept. 15. 1907. 



CALCULATIOlSr OF PROPER DILUTION OF DIPS. 25 

A'olume, but which are not volatile with steam. There seems to be 
no way of determining these bodies in the dip, provided they are 
phenoloids ; hence it seems necessary to define cresylic acid within the 
scope of the regulations as " phenols derived from coal tar, none of 
which boils below 185° C. nor above 250° C," and which are com- 
pletely volatile with steam at 100° C. The only resource, accordingly, 
is to handle the oils and cresylic acid in exactly the same way as the 
dips themselves are handled (page 13), by distillation of an appro- 
priate weight of the acidified oil in a current of steam, with the sub- 
sequent extractions and measurement as described. 

As might be expected, cresylic acid appears to contain a smaller 
per cent of these acid bodies not volatile wit-h steam than does creo- 
sote oil. Very probably the amount is subject to considerable varia- 
tion in different samples. Results on certain samples will be given 
in the section on experimental work (page 33). 

CALCULATION OF PROPER DILUTION OF DIPS. 
COAL-TAR CREOSOTE DIPS. 

The regulations of the Secretary of Agriculture " state that a 
coal-tar creosote dip " should contain when diluted ready for use 
not less than 1 per cent by weight of coal-tar oils and cresylic acid. 
In no case should the diluted dip contain more than four-tenths of 
1 per cent nor less than one-tenth of 1 per cent of cresylic acid; 
but when the proportion of cresylic acid falls below two-tenths of 
1 per cent the coal-tar oils should be increased sufficiently to bring 
the total of the tar oils and the cresylic acid in the diluted dip up to 
1.2 per cent by weight." 

In calculating from the composition of a dip its proper dilution 
under this regulation three points must be borne in mind. First, 
the regulations demand that hydrocarbons and phenols must be 
present in certain minimum percentages by weight, whereas in prac- 
tice a dip is always diluted by volume. Second, the regulations 
set two independent minimum pairs of values below which the per- 
centages of phenols and of hydrocarbons and phenols may not fall, 
though they may rise above these set values within certain liuiits, 
thus allowing a considerable range in the possible composition of 
a dip. Third, the calculated dilution uiust be the greatest possible 
dilution which the dip under consideration can obtain under the 
regulations. 

Three steps will then be involved in the calculation of the dilu- 
tion of a coal-tar creosote dip, (1) The selection of the pair of 
minimum percentages of phenols and of hydrocarbons and phenols 

" IJiireau of Animal Industry Order 14.'i. page 18. 



26 ANALYSIS OF COAL-TAR SHEEP DIPS. 

most advantajreous for tliat particular dip; (2) the calculation of 
the niaxiinum dilution by wei<i:ht which a dip of that composition 
can be trranted under the section of the rej^ulation most advan- 
tageous to it; (3) by employment of the specific jnrravity of the dip 
as a factor to pass from the obtained maximum dilution by weight 
to the maximum dilution by volume. 

These data having been thus fully set forth, it hardly seems neces- 
sary to enter into the actual solution of the problem, since the matter 
is purely one of nuithenuitics. It will be sufficient to state that a 
mathematical analysis of the above regulation will lead to the fol- 
lowing four cases and the four corresponding rules for obtaining 
the maximum dilution in each case: 

Case I. — When the percentage of phenols is less than (me-twelfth 
of the sum of the percentages of hydrocarbons and phenols. 

IJule: Multiply the percentage of phenols by 10, subtract 1 from 
the product, and multiply the remainder by the specific gravity of 
the dip. 

The diluted dip will then contain 0.1 per cent phenols and over 1.2 
per cent hydrocarbons and phenols. 

Ca.se II. — When the j^ercentage of phenols is between one-twelfth 
and one-sixth of the sum of the percentages of hydrocarbons and 
phenols. 

Rule: Divide the sum of the percentages of hydi'ocarbons and phe- 
nols by 1.2, subtract 1 from the quotient, and multiply the remainder 
by the specific gravity of the dip. 

The diluted dip will then contain 1.2 per cent of hydrocarbons and 
phenols and between 0.1 and 0.2 per cent of phenols. 

Case III. — When the percentage of phenols is between one-sixth 
and one-fifth of the sum of the percentages of hydrocarbons and phe- 
nols. 

Rule: Multiply the percentage of phenols by 5, subtract 1 from 
the product, and ipultiply the remainder by the specific gravity of 
the dip. 

The diluted dip will then contain 0.2 per cent phenols and between 
1 and 1.2 per cent hydrocarbons and phenols. 

Case IV. — When the percentage of phenols is between one-fifth 
and two-fifths of the sum of the percentages of hydrocarbons and 
phenols. 

Rule : Subtract 1 from the sum of the percentages of hydrocarbons 
and phenols, and multiply the remainder by the specific gravity of 
the dip. 

The diluted dip will then contain 1 per cent hydrocarbons and phe- 
nols and between 0.2 per cent and 0.4 per cent of phenols. 

In each case the result obtained by the rule is the number of parts 
by volume which may be added to one part by volume of the dip ; in 



EXPERIMENTAL WORK WITH METHODS OF ANALYSIS. 



27 



practice, the greatest number of gallons of water which may be added 
to one gallon of dip. 

It may be stated that if the percentage of phenols is greater than 
two-fifths of the sum of the percentages of hydrocarbons and phenols, 
the use of the dip can not be permitted under the regulations, for 
when diluted until it contains 1 per cent of hydrocarbons plus phenols, 
the minimum allowed, it will necessarily contain above 0.4 per cent of 
phenols, which amount is set as the maximum limit. 

CRESYLIC-ACID DIPS. 

The aforementioned regulations state in regard to the cresol dip 
that " when diluted ready for use this dip should contain one-half 
of 1 per cent of cresylic acid." From this may be derived the rule : 
Multiply the percentage of phenols by 2, subtract 1 from the product, 
and multiply the remainder by the specific gravity of the dip. 

EXPERIMENTAL WORK WITH METHODS OF ANALYSIS. 

Much experimental work was done in developing and testing the 
previously described methods of analysis. A brief outline of some 
of this experimental work, with a more detailed discussion of certain 
results, may be of interest. 

DETERMINATION OF PHENOLS. 

Particular difficulty was experienced Avith phenols. It early be- 
came clear that the most desirable method of finally estimating their 
amount would be by measuring the increase of volume shown by a 
solution of caustic soda when the phenols in question were absorbed 
by it. The general reasons for this conclusion have already been 
discussed. Attention will now be paid to some special points involved. 

I. When weighed amounts of pure phenols are shaken in the meas- 

weiffht phenols 
uring tube as described, and the coefficient volume increase NaOH 

determined, it was found that — 

(«) This coefficient is constant for a given phenol irrespective of 
the amount measured — within the limits of the tube — and of the 
presence or absence of other coal-tar hydrocarbons in addition to 
benzol. To illustrate, weighed amounts of a fairly pure cresylic acid 
were dissolved in benzol and sliaken in the measuring tube with 
caustic soda, with the following results: 



Weight of 


Increa.se in 


cresol. 


volume of 




NiiOH. 




Cubic cen- 


Grams. 


timeters. 


9.1386 


8.66 


9. '282.5 


8.62 


9.6160 


8.82 


2. 3893 


2.22 


2. 3228 


2.19 



Coefficient: 

(w eight phenol.s \ 
volunje increii.se NaOH./ 



1.055 
1.078 
1.079 
1.07ii 
1.060 



28 ANALYSIS OF COAL-TAR SHEEP DIPS. 

Althoufjh approximately four times as much cresol was employed 
in the first three trials as in the last two, the derived coefficient is 
practically identical. 

(b) This coefficient is not the same for all phenols, but varies in 
the same direction as the specific gravity of different phenols, though 
in greater ratio, accordingly varying inversely as the molecular 
weights of the different phenols and in approximately equal inverse 
ratio. For the mixtures of phenols ordinarily occurring in commer- 
cial cresylic acid and in the grades of coal-tar creosote oils commonly 
used for making dips, the average coefficient proved to be unity as 
nearly as could he determined. 

II. When weighed amounts of pure phenols were shaken in a 
separatory funnel with water, soda, sulphuric acid, and benzol in 
the proportions described in the analytical method, and the phenols 
then brought to measurement, the coefficients in all cases were found 
to run parallel to those obtained in Experiment I, but to be very 
slightly lower; that is, water is carried by the phenols into benzol 
solution in amount rather more than enough to balance the amount 
of phenols retained by the acid aqueous layer in the separatory 
funnel. No loss is therefore here involved. 

III. The validity of the method of measurement having been thus 
established, the next problem was to concentrate without loss of 
phenols the large volume of distillate resulting from the distillation 
of the acidified dip with steam to a volume sufficiently small to be 
introduced into the measuring tube. 

(a) The first attempt was concentration by evaporation of the 
liquid after rendering it strongly alkaline. Weighed amounts of 
phenols were dissolved in 800 c. c. of water and 25 c. c. of caustic 
soda 1 : 3, and evaporated to 40 to 50 c. c. on the steam bath, and the 
phenols were then separated and brought to measurement as de- 
scribed. It was found that this proceeding involved a loss averaging 
at least 5 per cent, the percentage increasing as the molecular weights 
of the phenols increased. This result could be expected, for the 
higher phenols, being of much less solubility in dilute caustic soda, 
and being more weakly acid and their salts consequently more easily 
hydrolyzed, would naturally suffer a greater percentage of loss than 
the lower, more acid phenols. 

(h) An attempt was next made to extract phenols from the dis- 
tillate with benzol, then concentrate the benzol solution by distillation 
to a residual quantity of about 60 c. c, which was lastly brought 
into the measuring tube with caustic soda. Weighed amounts of 
phenols were brought into a 1,500 c. c. separatory funnel with 800 
c. c. of water, and shaken with benzol in the amount and manner 
described in the analytical method (page 15), both with and with- 
out the addition of NaCl. Without addition of XaCl each extrac- 
tion with benzol removes at most but 75 per cent of the phenol 



EXPERIMENTS IN DETERMINING PHENOLS. 



29 



present each time; with 12| grams NaCl per 100 c. c. about 87 per 
cent is withdrawn, and with 25 grams per 100 c. c, between 92 and 
94 per cent is taken up by the benzol in each extraction. Three 
extractions as described will therefore account for 99.95 per cent 
of the amount of phenols originally present. This was eminently 
satisfactory. But when the benzol extract was submitted to distilla- 
tion, variable amounts of phenols were found in the distillate, the 
amount being almost negligible in the case of phenols of high boil- 
ing point, but considerable with the lower phenols, and especially 
notable in the case of benzophenol. 

(c) Attempt was next made to hold back phenols while benzol 
was being distilled as described in (Z>), by the addition of a few 
grams of metallic sodium, the idea being to eliminate the effect of 
small amounts of water and at the same time to bring the phenols 
into a completely nonvolatile compound. This attempt was quickh^ 
abandoned, for the reaction between sodium and phenols proved 
very slow and incomplete, even on long standing or boiling with 
reflux condenser. 

{d) It will be noted that high-boiling phenols suffer special loss 
by the method of (a) and low-boiling phenols by method (h), while 
the method of extraction of (b) is perfectly adequate. Therefore 
an attempt was made to combine the two methods by distilling off 
the benzol over strong caustic soda — 15 c. c. of 1 : 2 NaOH — the idea 
being that the strong caustic soda would hold nearly all the phenols 
in combination, and afford on account of its concentration but slight 
opportunity for hj'drolysis and formation of water vapor, while 
since those very phenols most subject to hydrolysis and loss from 
the caustic soda are those of high boiling point and but slight vola- 
tility with vapors of benzol, practically no appreciable amount of 
phenols would escape from the flask. This proved to be the case. 
Delicate qualitative tests show the presence of phenols in the dis- 
tillate, but in amount far beyond the power of the measuring tube 
to detect. 

The following table will illustrate some of the positive points 
brought out in Experiments I, II, and III. Purified cresol was 
employed, obtained in the laboratory from crude cresylic acid. 

Results of experiments upon the method for determining phenols. 



Method of treatment. 



Dissolved in benzol and shaken with NaOH 
in tube 

In separatory funnel with benzol, NaOH, 
and H2SO4, then as in analysis 

With 800 c. c. water, 200 g. NaCl. then 
treated as in analysis 



Weight Increase of 
taken. NaOH. 



Grams. 
6.855 

7.542 
7.773 
8.433 
9.776 
9.344 



j CuMc 

I cciili meters. 
6.69 
8.50 
7.52 
7.75 
8.30 
9.81 
9.40 



CoelBcient: 
weight phenols \l 
volume increase NaOH./ 



1.023 
1.015 
1.003 
1.003 
1.016 
.997 
.998 



Mean co- 
efficient. 



1.019 



80 



ANALYSIS OF COAL-TAR SHEEP DIPS. 



It is evident, accordingly, that the method described will bring to 
measinvnu'iit, with no loss, all the phenols present in the distillate 
from the dip. 

TKSTS WITH COAL-TAR CREOSOTE DIPS OF KNOWN COMPOSITION. 

The next undertaking was to make up a coal-tar creosote dip of 
accurately known composition in order to test upon it the validity 
in practice of the methods of analysis developed. 

Dip No. 1. — Rosin : A fair grade of ordinary commercial rosin was 
emj)loyed. Weight used, 220 grams. 

Hydrocarbons: Coal-tar oils, supposed to be free from phenols, 
shaken four times with 10 to 25 per cent caustic soda, dried over 
calcium chlorid, and filtei-ed. Weight taken, 550 grams. 

Pure phenols: Obtained by the purification in the laboratory of 
crude cresylic acid. Weight taken, 120 grams. 

Caustic soda and water: One part pure NaOH dissolved in two 
parts water. By titration with N/2 H.SO4 and methyl orange the 
solution showed 24.7 per cent Na.O and 75.30 j^er cent water. 
Amount taken, 00 grams, which accordingly contained 00 X 0.247 = 
22.23 grams Na^O and 00 X 0.753 == C7.77 grams water. There was 
also added 20 c. c. water, making the total water used 87.77 grams. 

The dip accordingly contained : 





Grams. 


Per cent. 


Water - 

Soda (NasO) 


87.77 
22.23 
220.00 
120.00 
550.00 


8.78 
2.22 
22.00 
12.00 
55.00 


Rosin 


Phenols 


Hydrocarbons and pyridin- 




1,000.00 


100.00 



Saponification was effected in a flask connected with a reflux con- 
denser and immer.sed in a water bath. 
Analysis of dip No. 1 gave : 



Water 

Soda- 

Pyridin 

Phenols 

Rosin acids, gravimetric 

Rosin apids, volumetric. 



A. 


B. 


Percent. 


Per cent. 


8.8 


8.6 


2.15 


2.17 


1.19 


1.90 


11.78 


11.74 


19.90 


19.80 


Ul)20.03 


(1)19.94 


{(2)19.97 


(2)19.81 



Mean. 



Per cent. 

8.7 
2.16 
1.25 
11.76 
19.85 

\ 19.94 



It will be noted that, as was to be expected, the amount of rosin 
acids found is about 00 per cent of the rosin used in the dip. The 
results seemed very satisfactory, except perhaps in the case of the 
phenols. (But see page 35.) 



TESTS WITH COAL-TAR DIPS OF KNOWN COMPOSITION. 



31 



Dip No. 2. — ^Made up more as a dip would be made in practice. 
Rosin, 200 grams. 

Coal-tar oils which were used gave on analysis : 





A. 


B. 


Mean. 


Water ... 


Per cent. 
0.40 
3.35 
20.30 
75.95 


Percent. 
0.50 
3.56 
20.40 
75. &i 


Per cent. 
0.45 


Pyridin . . . 


3.45 


Phenols. -.- _ _ .... 


20.35 


Hydrocarbons, by diflference. . . . .. . _. 


75.75 








100.00 


100.00 


100.00 



Amount taken, 700 grams, which would give: 

Grams. 

Water 700X0.0045= 3.15 

Pyiidiu 700X .0345= 24.15 

Phenols 700X .2035=142.45 

Hydrocarbons 700X .7575=530.25 

Soda and water: By titration with X/2 H^SO^ and methyl orange 
the solution was found to contain 25.22 per cent NagO and 74.78 per 
cent HgO. Ninety grams of the solution were employed, giving 22.7 
grams Na^O and G7.3 grams H^O. There was also added 10 c. c. of 
water. The materials were all put together in a 1,500 c. c. flask and 
the latter was stoppered and shaken frequently until saponification 
was complete, with application of no external heat. 

The dip accordingly contained: 

Per cent. 

Water ( 0.32-1- 6.73 -h 1.0) S. 05 

Soda (Na^O) 2.27 

Pyridin 2.42 

Rosin 20.00 

Phenols 14. 25 

Coal-tar hydrocarbons 53.01 

Total 100.00 

Analysis gave the following results: 





A. 


B. 


Mean. 


Water. . . . „ .- 


Per cent. 
8.10 
2.28 
2.28 
"18.66 
14.16 
' .'>4.52 


Tercent. 
8.30 
2.26 
2 ''1 

"liiso 

14.06 
54.37 


Percent. 
8.20 


Soda .. 


2.27 


Pyridin - 


2.25 




18.73 




14.11 




54.44 








100.00 


100.00 


100.00 



' Volumetrlp. 



* Gravimetric. 



Results from this dip ai)pear very satisfactory. It sliould be noted 
that the formuhis employed in the experimental dips are in no way 
recommended for a(;tual use. The immediate object was not to make 
a superior dip, but merely to test the methods of analysis employed. 



32 ANALYSIS OF COAL-TAR SHEEP DIPS. 

TEST WITH CRESYLIC ACID DIP OK KNOWN COMPOSITION. 

The next experiments were to test in the same way the validity of 
the methods when applied to cresylic acid dips. Dip No. :i was ae- 
cordin<^ly made somewhat along the lines of the U. S. P. formula for 
liquor cresolis compositus. 

One hundred and seventy-five grams of linseed oil was saponified 
in a beaker with 81 grams of a solution of pure KOH, shown by titra- 
tion with N/2 1X2804 and methyl orange to contain 35.9 per cent of 
K/) and i'A.l per cent H2O. Accordingly 8lX0.:i59=21).08 grams 
K2O, and 81X0.041 = 51.92 grams H^O were introduced. The beaker 
with its contents was weighed before and again after saponification, 
and a loss of 8.5 grams noted, leaving in the soap finally 51.92—3.5=: 
48.42 gi'ains of ILO. The materials employed in the soap were then — 

Grams. 

Linseed oil 175.00 

Potasli (K=0) 29.08 

Water 48.42 

Total 252. 5 

Now, taking as the mean molecular weight of the fat acids of lin- 
seed oil the number 284.7," and as the molecular weight of glycerin 
the number 92, the mean molecular weight of linseed oil will be 
3 (284.7) +92— 54=892.1. The 175 grams of linseed oil will then be 
equivalent to — 

92 
Glycerin, 175 X;jrr-T= 18.03 grams. 

854—27 
Fatty acid anhydrids, 175 X =162.25 grams. 

54 
But this glycerin will take up 18. 03 X r-^, =5.28 grams H^O in the 

process of saponification of the linseed oil, hence the completed soap 
theoretically consists of — 

Grains. 

Glycerin 18.03 

Fatty acid anhydrids 162.25 

K2O 29. 08 

Water (48.42—5.28) 43.14 

Total -._ 252.50 

The soap was transferred to a tared liter flask with the aid of 
U. S. P. cresylic acid (cresylic acid from two different manufac- 
turers being mixed in equal parts to secure a fair sample), the con- 
tents were brought to 500 grams with cresylic acid, and the flask 
was .stoppered and frequently shaken for several days till a uniform, 

° I^nvkowitscli, .7. Chemical Technology and Analysis of Oils, Fats, and 
Waxes, 3d Ed., vol. 1, p. 334. 1904. 



TEST WITH CRESYLIC ACID DIP OF KNOWN COMPOSITION. 33 

clear liquid resulted. The mean of four analyses (page 34) showed 
the U. S. P. cresol employed to be 98.80 per cent pure. The amount 
used was 500 — 252.5=247.5 grams, containing accordingly 247.5X 
0.988=244.53 grams phenols and 247.5X0.012=2.97 grams of pyri- 
din, hydrocarbons, etc. 

Analysis of the dip ought then to show : 

Per cent. 

Water 8. 63 

K2O 5. 82 

Fatty acid anhydrids -_ 32.45 

Glycerin 3. 61 

Phenols 48.90 

Pyridin, hydrocarbons, etc 0.59 

Total 100. 00 

Actual analysis of this dip gave the following results : 



A. 



Water 

K2O 

Fatty acid anhydrids- 

Glycerin 

Phenols 

Pyridin 



B. Mean. 



8.1 


8.0 


8.05 


5.71 


5.72 


5.71 


31.50 


31.39 


31.45 


3.50 


3.49 


3.50 


48.77 


48.98 


48.88 


0.28 


0.28 


0.28 



TESTS FOR NONVOLATILE ACID UODIES IN COAL-TAR CREOSOTE AND COM- 
MERCIAL CRESYLIC ACID. 

Mention has already been made of the fact (page 24) that both coal- 
tar oils and commercial cresylic acid may contain bodies of an acid 
nature, absorbed by caustic soda solution with a consequent increase 
in its volume, but which are not volatile with steam at 100° C. These 
acid bodies very probably vaiy in amount in different samples of oils 
and cresols, and may not be present in every case. Examinations 
were made of the coal-tar creosote oil employed in making dip No. 2, 
and of the U. S. P. cresol used in dip Xo. 3. 

The coal-tar creosote oil used in preparing dip Xo. 2 was found to 
contain by distillation of the oil with steam 20.35 per cent phenols, as 
the mean of the two results 20.30 per cent and 20.40 per cent. The 
oils were then handled in another way, namely, 100 grams were dis- 
tilled from an Engel flask to 300° C. The first portion of the distil- 
late containing water was received in a small stoppered cylinder, ben- 
zol and XaCl were added, the cylinder was shaken, and after .separa- 
tion had taken place the benzol was pipetted out and added to the rest 
of the distillate. Extraction of the aqueous portion was repeated 
several times in the same way. The total oily distillate was made to 
a definite volume with benzol, an aliquot part shaken with caustic 
soda in the measuring tube and the increase in volume noted. Some- 



34 



ANALYSIS OF COAL-TAR SHEEP DIPS. 



what variable re.sults were obtained, ranj^ing between 21.80 and 23.20 
for the per cent of phenol.s found by this method in the creosote oil. 

In the examination of the U. S. P. cresol used in dip No. 3 weighed 
amounts of the cresol were introduced into a 150 c. c. separatory fun- 
nel, with 15 c. c. of 1 : 2 XaOH and 30 to 40 c. c. Avater, then benzol 
and H.SO^ added, and, in short, the last two steps of the adopted 
analytical method were followed in detail until the phenols were 
brought to measurement. 

Treated in this way 9.059 grams cresol gave 9.13 c. c. increase in 
volume of XaOH= 100.77 per cent phenols; 8.146 grams cresol gave 
8.15 c. c. increase in volume of NaOH= 100.05 per cent phenols. The 
U. S. P. cresol will then appear by this method to contain 100.41 per 
cent phenols, the mean of the two results obtained. 

Phenols were now determined exactly as they would be in a dip, 
by steam distillation of weighed amounts of the U. S. P. cresol. 



Weight 
cresol. 


Increase 

in volume 

NaOH. 


Per cent 
phenols. 


Orams. 
9.457 
9.590 
9.468 
9.105 


Grams. 
9.40 
9.46 
9.36 
8.95 


99.40 
96.64 
96.86 
-98.30 



The mean of these results is 98.80 per cent, while the range of dif- 
ference between the results is about 1 per cent of the amount of 
plienols operated upon. AMien working with nearly pure phenols it 
is difficult to obtain results which check as closely as desirable, for 
the meniscus is subject to considerable variation in shape and degree 
of curvature. This variation in the form of the meniscus appears to 
a less extent when the phenols from a cresol dip are measured, and 
is practically absent in case the phenols have been obtained from a 
creosote dip, hence readings in these cases check more closely. lai 
practice results may reasonably be expected to check within this 
limit of 1 per cent of the total amount of phenols in all cases ; that is, 
results on a cresol dip containing 50 per cent phenols agree within 
0.5 per cent, and those on a creosote dip containing about 10 per cent 
phenols within 0.1 per cent. 

It is accordingly evident that both coal-tar creosote oils and even 
quite pure cresylic acid may contain bodies of an acid nature, which 
may possibly be phenoloids, but for the determination of which, 
since they are not volatile with steam, there appears at present no 
possible means. In the actual analysis of a dip these bodies will 
naturally tend to increase the percentage of rosin acids found, 
whether the latter are determined gravimetrically or volumetrically. 
It is not likely, however, that in any case the percentage of rosin 
acids will be thus increased to a figure greater than the per cent 



SUMMARY OF RESULTS. 35 

of rosin actually employed in making the dip, as is indicated 
by the result for rosin acids obtained in the analysis of dip Xo. 2. 
As already shown, the creosote oil used in this dip contained a consid- 
erable amount of nonvolatile acid bodies. The existence of these 
nonvolatile acid bodies was not known at the time dip No. 1 was 
made and analyzed. Unfortunately, no more of the purified cresylic 
acid used for that dip was available for examination: but inasmuch 
as it was prepared from a very crude commercial product, it undoubt- 
edly contained an appreciable amount of these nonvolatile acid bodies, 
whose presence may account for the somewhat low results for phenols 
obtained in the analysis of that dip. 

SUMMARY. 

In conclusion certain points ma}" be emphasized : 

1. Methods appear now available for determining with consider- 
able accuracy the constituents of coal-tar creosote and cresylic acid 
dips. These methods are not especially tedious, nor, while requiring 
a certain amount of practice for their successful execution, do they 
demand complicated apparatus, exceptional skill in manipulation, 
or the liberal use of expensive chemicals. The results are all obtained 
by fairly simple volumetric processes, and the closeness with which 
experience in this laboratory has shown them to check, whether ob- 
tained by the same or different operators, renders the methods herein 
described particularly adapted to the standardization of dips. 

2. Methods exactly parallel to the methods employed in the 
analysis of dips may be applied to the valuation of creosote oil and 
cresylic acid which are to be used in making dips. If a dip is prop- 
erly made from analyzed materials and the dip itself then analyzed, 
the actual analysis of the dip Avill agree very closely with its calcu- 
lated composition. The validity of the methods of analysis is thus 
doubly confirmed. 

3. Furthermore, the agreement between the analj^sis of a dip made 
from analyzed materials with its calculated composition indicates 
that it is actually possible for a manufacturer to place on the market 
a dip of practically unvarying composition. 

O 



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