July, 19 I 2
T H E J O liRA\’A
L OF I S D C-STRIAL A N D EIYGIA‘EERISG CNEdlISTRY .
both the iodine and the oil could be dissolved and o u t of which the solidified product separated readily so t h a t it might be removed from the liquid portion; furthermore, t h a t this liquid portion could be dissolved in a petroleum solvent boiling under 80’ C. while the solid product from the china wood oil was practically insoluble in this solvent. Based upon these facts the following method of analysis was devised: Weigh into an Erlenmeyer flask about 5 grams of the oil to be examined, add to it I O cc. of 991i2 per cent. acetic acid and after warming i t so t h a t there is a perfect mixture of oil and acid, add to it 50 cc. of a solution of iodine in 991,’~per cent. acetic acid containing 1 5 grams of iodine per liter. The acetic acid solution of iodine should be warmed so t h a t when added to the oil solution t o be tested it will not chill it. Upon adding the iodine solution there results a n almost instantaneous separation of some solid product from the solution in large amount. The solution is allowed t o rest for half a n hour t o insure complete reaction and then 50 cc. of petroleum solvent (b. p. below 80’ C.) added and allowed t o mix thoroughly with the contents of the flask. The liquid is then drained off from the flask into a separatory funnel and another portion of 50 cc. of petroleum solvent added t o the solid residue which has been allowed to remain in the flask so as to wash out of i t the residue of liquid products; after pouring off this solvent the solid residue is extracted a third time with 50 cc. of petroleum solvent, the solutions being united in the separatory funnel. Water is now added t o the contents of the separatory funnel and this causes a separation of the liquid into two layers, one of petroleum solvent carrying the liquid portions of the reaction in solution and the other of water united with acetic acid. This latter is drawn off and the petroleuni solvent repeatedly washed with water till it is free from acetic acid and then shaken out with a solution of potassium iodide t o remove free iodine which may be present; after a final washing with water it is transferred t o a flask, the solvent evaporated off and the residue weighed. The weight of this residue is a measure of the proportion of those constituents of the oil under examination which are not solidified b y the action of iodine. Broadly stated, the process gives results showing t h a t only a small fraction of china wood oil remains liquid at the conclusion of this process while other oils remain entirely liquid and soluble in the petroleum solvent and if the process be applied to known mixtures of a given sample of china wood oil with soya bean oil t h e proportion of soya bean oil map be determined with reasonable accuracy. I n order to make such a determination, however, upon oils of unknown origin, it is necessary t h a t the per cent. of liquid products which may conveniently be described as “per cent. of soluble iodides” of true china wood oil and also the variation in this per cent. given by different varieties and samples of true china wood oil should be known. I n order to investigate this matter i t is necessary to obtain a considerable number of authentic samples of such oils and these samples are to be ob6
497
tained only in China and in the other countries where this oil is produced. The method is, however, submitted as one suitable for the investigation of the oil and particularly as a method for determining the grade of the oil in respect t o its most characteristic property. As the writer has been unable to obtain any considerable number of original small samples of the oil, he, refrains from giving the exact figures obtained upon the commercial samples which have been examined but hopes that others may apply the process to authentic samples as they are obtained. 7
EAST42ND STREET,
N E W YORK.
ON THE INDICES OF REFRACTION OF CHINA W O O D OIL. B Y LOUISELSBERC WISE Received May 1 1 , 1912.
The increasing use of china wood oil in the paint and varnish industries has created the necessity for a proper examination and standardization of this important article of commerce. Much of this drying oil is sent to European and American ports through Hankow, and a rumor is now current t h a t there have been varied attempts to adulterate these shipments with cheaper products, such as soya bean oil. Whether or not these reports are based on fact, the author of this paper is in no position t o decide, b u t he has found it a proper time to review the recent literature, relating t o the characteristic properties of the raw material, and to find, if possible, some method by which the purity of the oil could be gauged. The important characteristics of the oil1 are its odor, its peculiar drying properties (in which i t differs markedly from linseed), its high specific gravity and its coagulation on heating. The saponification, iodine and acid numbers appear to be of little value in judging the oil. The jelly which is formed on application of heat is elastic and insoluble in the common solvents. I t is ordinarily believed t h a t the gelatinization is due to a polymerization; i t is undoubtedly not caused by oxygen absorption, and i t immediately distinguishes wood oil from the other common drying oils. Several chemists’ have recently made a study of the physical characteristics of the “go-back” (the varnish maker’s name for this coagulation product), and a number of chemical examinations,, have been made, which up to the present have led t o widely divergent results. A further investigation of the “go-back,” as well as the relation between its properties and its technical use, is being made by Mr. Eugene G. Bloch, of our laboratory, and the results of this research may be published a t some future date. Another striking peculiarity of the oil is its high index of refraction. Lewkowitsch states t h a t the refractive index is much higher than t h a t of any other drying oil, and this statement suggested the study of t h e refractive indices of a number of commercial Lewkowitsch, Chemical Technotogy of O h , Fats and Waxes, 2 , 6 2 . Private communication. a Lewkowitsch, S, 99. Nash, Priiate communication to Lewkowitsch. Norman, Chem. Zto, 99 (1907). 1
2
T H E J O L - R S A L OF I N D C S T R I A L AA’D E S G I S E E R I S G C H E d f I S T R Y .
498
samples. The data obtained is recorded in the tables given below.* All attempts t o get samples of wood oil of known source and purity were without avail. The difficulty was due t o the primitive condition in the collection of the oil and its shipment t o the coast from the country districts of China.1 We received a sample from Mr. Bacon (also purchased on the open market) which is supposed t o be a standard, b u t its source has not been indicated. The results tabulated below, therefore, represent the refractive indices of courtmylercial wood oils shipped t o us for use in the manufacture of varnish. The shipments cover a period of approximately eight months, during 1911-1912. Some of them have proved unsatisfactory in the processes of manufacture, and there is some indication that a relation exists between the refractive index and the “working quality” of the oil. That question can be settled only by a f a r more extended research. Gross adulteration is certainly indicated very clearly and rapidly by the use of the refractometer, and whether foreign oils, present in small quantities may be detected, will depend very largely on the results of future cooperative investigation. TABLEI . Index of refraction Mark. at 25’ C. A.3.20.12.. . . . . . . . . . . . . . . . . . . . . . . . 1.5148 A No. 1 A . . . . . . . 1.5118 1.5130 A K o . 3 4 ........................ 1.5164 A No. 4 4 . . . . . . . . . . . . . . . . . . . . . . . . 1.5153 A No. 9A (R.Y.S. 3534) . . . . . . . . . . 1.5154
......................
1.5168 Mr. Bacon . . . . . . . . . . . . . 1.5186
c&\c
.........................
1.5121
.....................
1.5116
....................... C /s;‘.,C.. A N o . 19 .......................... R . M . S. 3 5 0 5 . . . . W. K . C. \I7.0
....................
.
1.5167 1.5163 1.5099 1.5110
The results in Tables I1 and I11 require little comment; they show clearly t h a t the admixture of small amounts of other drying oils lowers the refractive index. TABLE11. Sample. Index of refraction at 25’ C. wood oil (mark) A . 3 . 2 0 . 1 2 . .. . . . . . 1.5147 wood oil, 5 per cent. soya bean oil 1.5122 wood oil, 5 per cent. linseed oil. . . . 1.5128 wood oil, 10 ge soya bean o i l . . linseed oil.. . . .
100 per 95 per 95 per 90 per 100 per 100 per
cent. cent. cent. cent. cent. cent.
100 per
TABLE111. Sample. Index of refraction at 25 C. cent. u.ood oil (Bacon’s sample). . . . . . . . . 1 ,5186 cent. wood oil. 5 per cent. soya bean oil 1.5163 cent. wood oil, 5 per cent. tallow o i l . , , , , 1.5161 cent. tallow o i l . . ...................... 1.4833
95 per 95 per 100 per
All indices of refraction were taken without the use of water circulation. All refractometric readings were made in the Advanced Physics Laboratory of Columbia University.
* The explanation of these high refractive indices will probably be found in the examination of the chief constituent of the oil, namely, the remarkable glyceride of oleomargaric acid, which is present in none of the other common drying oils. 1 Private communication.
July,
1912
I n conclusion, I beg t o thank Mr. Bloch, chemist for the Standard Varnish Works, for his material aid, Dr. C. C. Trowbridge, of the Department of Physics of Columbia University, for his kind advice and.Dr. Parker C. McIlhiney for his just criticism and his help. LABOR.4TORIES
OF T H E STANDARD VARNISH W O R K S .
ELM PARK,N. Y.
THE REFRACTIVE INDEX OF BEESWAX.’ B Y L FELDSTEIN. Received Jan. 5, 1912.
Lewkowitsch, in “Chemical Technology and Analysis of Oils, Fats, and Waxes,” recommends refractometric examination as a preliminary test in the examination of beeswax, giving as the limits between which pure beeswax should fall, 42 .9‘-45.6 O ; butyro-refractometer scale, calculated t o 40’ C. These figures were obtained from the work of Werderl and Berg,j who made the determinations at temperatures ranging between 70’ and 84’ C. and then calculated them t o 40’ C. Seither Werder nor Berg in their original articles give the figures actually observed nor explain how their calculations were made, but it is assumed t h a t they added to the observed figures the correction 0 . 5 5 O butyro for each degree centigrade between the observed figures and 40’ C., the correction value 0 . 5 5 O being generally used for all fats and oils when calculated to 40’ C. I n this laboratory a n AbbeZeiss direct-reading refractometer is used, and for beeswax a correction of 0.00037 per degree centigrade was found necessary. This figure was obtained by taking the refractive index a t 6 j O , j j O , and 8 j O C. and dividing the difference in the reading by the difference in degrees centigrade. This correction of 0.00037 per degree centigrade was found t o be practically constant between these temperature limits not only for all pure beeswax examined, b u t also for those which, upon further examination, showed adulteration. As beeswax is a solid a t 40’ C. and the refractive index is always read on the melted wax a t some temperature above 63’ C., i t seems desirable t o eliminate the use of the calculation to 40’ C. and t o set limits for the refractive index of pure beeswax a t some temperature above the melting point. For this purpose a number of samples of known purity and origin, obtained from the Bureau of Entomology, Cnited States Department of Agriculture, and some others purchased on the open market were examined. All of these have been analyzed by the drug laboratory of the Bureau of Chemistry. The readings were made a t 6 5 ” , j s o , and 8 j o C., and the results are given in the following tables. Table I consists of the figures obtained on the samples of pure beeswax secured from the Bureau of Entomology. Table I1 shows the results on those samples obtained in the open market, many of them adulterated samples. I n the column headed “Remarks” are placed conclusions as to the nature of the sample based on the chemical analysis: 1 Contribution from the Contracts Laboratory, Bureau of Chemistry Washington, D. C. 2 Chem. Ztg’., 22, 59 (1898). Ibid.. 27, 752 (1903).
