ANALYTICAL EDITION
298
Vol. 6 , No. 4
sealed. The charg-
In the dehydration of the lower alcohols (ethyl, propyl, and butyl) the gaseous olefin passes out at P, water and undecomosed alcohol collecting in receiver 0, whereas in the case of Kigher alcohols such as amyl, liquid olefin also condenses in the receiver.
plug of gJass wool at L. Heat loss is cut down by the insert i o n of asbestos packing at M and N into t h e a n n u l a r space between the catalyst tube and the furnace block. Receiver 0 can be emptied without dismantling the apparatus, by application of pressure at P with a bulb aspirator, stopcock&being open and stopcock R closed.
This apparatus can be used for any catalytic reaction in which a vaporized liquid is passed over a solid catalyst a t approximately atmospheric pressure-dehydrogenation, dehydration, dehalogenation, etc. Also by the addition of a gas inlet tube a t I , catalytic reactions can be run in the presence of a gas-oxidation, halogenation, hydrogenation, hydration, etc.
ing rate is visible at J. The catalyst is held in place by a perforated glass partition at K and by a
LITERATURE CITED “Catalysis in Organic Chemistry,” p. 351, D. Van Nostrand Company, N. Y . , 1923. (2) Vaughen, IND. ENG.CHEM.,Anal. Ed., 4, 346 (1932). (1) Sabatier,
RECEIVEDMarch 26, 1934.
Thiocyanogen Number WILLIAMJ. WILEYAND AUGUSTUSH. GILL,Massachusetts Institute of Technology, Cambridge, Mass.
T
HE thiocyanogen number is a very useful method of
determining the composition of oleaginous bodies having oleic and linoleic acids or glycerides as constituents.’ With tests conducted according to the customary procedure, however, it seems to be subject to considerable inaccuracy. The usual method of analysis requires 25 cc. of thiocyanogen solution equivalent to 25 cc. of 0.1 N thiosulfate and 0.2 gram of the oil to be analyzed. Since there must be a 50 per cent excess, only 12.5 cc. are used in the reaction. I n the analysis for the iodine number the 25 cc. of Hanus iodine solution are equivalent to approximately 50 cc. of 0.1 N thiosulfate. It is apparent, therefore, that the accuracy of the thiocyanogen number is much less than that of the iodine number, when 25 cc. of solution and 0.2 gram are used in the analysis. I n order to make the thiocyanogen number as accurate as the iodine number, as it should be, since it must be in conjunction with the iodine number in these analyses, it appears that samples of double in size should be used. In order to determine the effect of a larger sample, five different samples of olive oil were analyzed with 0.2 gram of sample and 25 cc. of solution and with 0.4 gram and 50 cc. of solution. In both cases, the thiocyanogen solution was added from pipets having glass stopcocks on the outlets, in order to give greater accuracy than could be secured from a buret.
TABLEI. RESULTS OF THIOCYANOGEN ANALYSES SAMPLE 1
2
3
4
5
72.78 71.49 72.63 74.46 74.80
73.17 73.42 72.62 78.35 82.97
73.00 74.60 74.39
75.58 75.53
0.2 QRAM 25 CC. E 8 E D
78.05 77.32 77.36 74.00 73.89
77.07 76.55 77.41 75.98 73.52
75.84 76.28 75.63
75.21 75.37 75.69
74.72 73.21 72.92 67.59 68.11 0.4 GRAM 60 CC. U S E D
75.49 75.73 76.00
...
A very wide disparity was encountered in the 0.2-gram sample analyses-a difference which is much greater than would ever be secured in an iodine number. It is obvious. that these analyses would lead to very inaccurate results in the linoleic and oleic acid determinations since the error is so great. With the 0.4-gram sample and 50 cc. of thiocyanogen solution excellent checks were secured. With the exception of the first analysis of sample 4, all were well within the limits of accuracy of the iodine determination. It is therefore recommended that the determination of the. thiocyanogen number should be made with 0.4-gram sample and 50 cc. of thiocyanogen solution. RECEIVED March 20, 1934. 1 Jamieson, G. S., “Vegetable Fats and Oils,” p 345, Chemical Catalog Co., N. Y . , 1932.
Solution of Dificultly Soluble Copper Ores T. H. WHITEHEAD, University of Georgia, Athens, Ga.
I
T HAS been known since the time of Fresenius that sulfide ores of copper may often be extremely difficult to get into solution for analysis. When treatment with mineral acids and ordinary aqua regia fails to effect solution, the author has found that the acid mixture recommended by Bonilla (I) for dissolving nickel metals is very effective. This mixture consists of 40 volumes of 15 M nitric acid and 3‘volumes of 12 M hydrochloric acid. Samples of ore from 0.150 to 3.0 grams are usually dissolved by 43 cc. of the mixture, after boiling for half an hour.
The excess nitric and hydrochloric acids are easily removed by adding 20 cc. of 18 M sulfuric acid after the above treat-ment and heating until the total volume is reduced to 10 cc. This solution can then be diluted with water and the copper’ determined either iodometrically or electrolytically accord-. ing to standard procedures. LITERATURE CITED
(I) Bonilla*c*F.# IN=*ENG* CHnxM.9 RECEIVED June 8,1934
Ed.* 41 12’ (1932)*
