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of 5 per cent silver nitrate. The mixture was allowed to stand for several hours and filtered. The precipitate was dried to constant weight a t 110" C.: 100 25 M. W. of AgCl Weight of X'aC1 X X X M. w.of NaCl -
mo mo
weight of NaCI X 0.02453
=
weight of AgCI (calculated)
19.8083 X 0.02453 = 0.4859 gram of AgCl (calculated) 97 PER CENT SODIUM CHLORIDE-3 PER CENT SODIUM HYDROSULFIDE MIXTUFLE. The procedure was the same as that o u b lined above, except that the mixture was obtained by weighing out 19.4000 and 0.6000 gram of sodium chloride and sodium hydrosulfide, respectively:
19.4000 X 0.02453 = 0.4759 gram of AgCl (calculated) 94 PERCENTSODIUM CBLOFSDE-~PERCENTSODIUM HYDROSULFIDE MIXTURE. The procedure w~taagain the same as that outlined above, with the exception that the original mixture was
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composed of 18.8000 grams of sodium chloride and 1.2000 grams of sodium hydrosulfide : 18.8000 X 0.02453 = 0.4611 gram of AgCl (calculated) The results are given in Table I. The average error of nine analyses on three samples is -0 08per cent; thegreatest individual error is -0.19 per cent. The reproducibility and accuracy, as seen from these results, are excellent. Work is now in progress on the quantitative determination of the sulfide content of these mixtures. These results will be published a t a later date.
Literature Cited (1)
Khadanov, P., Chimie & Industrie, 31, 416 (1934)
(2) TopsBe, 2. anal. Chem., 22, 5-10 (1883). (3) Volhsrd, J., J. prakt. Chem., 117, 217 (1874). (4) Wyler, J. A,, Color Trade J., 9, 159-61 (1921).
Determination of Carotene in Vegetable Oils without Saponification EMANUEL BICKOFF WD KENNETH T. WILLIAMS Western Regional Research Laboratory, Bureau of Agricultural Chemistry a n d Engineering, Albany, Calif.
T
HE increasing research on carotene and its use in vegetable oil solutions has called attention to the desirability of a simple, accurate method for determining the carotene content of such solutions. The methods at present available are either too long and tedious or are subject to errors which may in some cases be large. The more rapid methods depend upon the determination of total color by simple dilution of the oil sample with a suitable solvent and measurement of the percentage of light transmission by the solution. Data presented in this paper show that this method may be in considerable error because of the presence of colored substances t h a t form during storage of the carotene solutions and which are included with the carotene in the analysis. The longer methods, which are the more accurate, all require that the sample be saponified. The Guilbert method (4) as modified by Peterson et al. (10) and by Peterson (9) may be regarded as representative of the saponification methods. Following the saponification approximately 12 phasic partitions are made in separatory funnels. Caution is necessary to prevent the formation of rather stable emulsions in this process. The noncarotene chromogens are removed by partition between nonmiscible solvents or by use of chromatographic adsorption columns ( 2 1 ) .
Selection of Adsorbent A rapid chromatographic method without the timeconsuming saponification and phasic separations is desirable. Vegetable oil solutions of carotene and noncarotene chromogens were dissolved in petroleum ether and analyzed for carotene, using the adsorbents suggested by Moore (7), Kernohan (6), and Wall and Kelley (14) for the analysis of plant extracts. It was found that these adsorbents were not directly applicable to oil solutions, as the presence of the oil interfered with the adsorption of the noncarotene chromogens by the dibasic calcium phosphate, sods ash, and magnesium oxide-Celite columns. In the method of Fraps, Kemmerer, and Greenberg ( 3 ) special techniques are required for preparing the adsorbents, and the degree of activation may vary on storage, so that their activity must be redetermined each time they are used. For these reasons no attempt was made to apply the method to analysis of solutions containing oil.
Seaber analyzed oil samples for carotene by saponification, removal of alkali and alcohol, transference of carotene to petroleum ether and adsorption of the carotenoids on aluminum oxide standardized according to Brockman, and eluting the carotene with 3 per cent acetone in petroleum ether. Thaler (IS) prepared chromatograms of various fats and oils on Tswett columns of aluminum oxide in order to detect the presence or absence of artificial colors in the oils, but made no attempt at a quantitative separation of the carotene from the other associated pigments. This work suggested t h a t aluminum oxide (
