ANALYTICAL EDITION
26
A derris sample (No. 594-B), yielding 6 per cent rotenone by the carbon tetrachloride method, also gave 6 per cent when extracted for 4 hours with acetone, followed by crystallization from carbon tetrachloride. A cub6 root sample (No. 686-G), giving 6.3 per cent rotenone by the carbon tetrachloride method, gave about the same value when extracted for 4 hours with acetone and the rotenone crystallized from carbon tetrachloride. It is evident that acetone extracts the rotenone in a much shorter time than carbon tetrachloride, probably because it is a better solvent for the resinous material in which the rotenone may be incorporated. However, the total material extracted by acetone amounts to more than that extracted by carbon tetrachloride, Consequently, in extractions such as the two just cited, a very considerable proportion of the dried acetone extract was insoluble in hot carbon tetrachloride. This necessitated filtration and numerous washings of the dried extract with hot carbon tetrachloride. The rotenone obtained in several tests made by this method was less pure, and, probably because of this, amounted to several tenths of a per cent more than that obtained by the carbon tetrachloride extraction method. This modified method thus has certain objections, although it may be useful when a rapid but approximate estimate of the rotenone content is desired. Because of the high optical rotation of rotenone (in benzene [or]'%" = -224" for a 5 per cent solution) it was thought that a method for its determination might be based on this phenomenon. Extractions were made with such solvents as acetone, benzene, chloroform, and ethylene dichloride. The extracts were made to a definite volume, and the optical rotation was measured in a saccharimeter. By use of data previously obtained (11) the amount of rotenone represented by the rotation was calculated. The values obtained in this way for rotenone in two samples of derris root (Nos. 402 and 407) and one sample of cub6 root (No. 584) were about twice those obtained by crystallization from ether or carbon tetrachloride. The optical rotation of an extract of one derris root (No. 412) indicated a content of over 5 per cent rotenone and that of another (No. 406) over 3 per cent, whereas neither of these samples gave any rotenone by crystallization from carbon tetrachloride extracts. The extract of one derris sample (No. 401) was dextrorotatory. Such erroneous values as the above may be expected, since there are numerous variable constituents of these extracts whose optical rotations are not known. It is thus evident that the optical rotation of the extract cannot be used as a measure of the amount of the rotenone present in the root. COXCLUSIONS The carbon tetrachloride extraction method outlined gives good results for the rotenone content of thoroughly airdried derris roots, cub6 roots, and haiari stems. The results of numerous extractions indicate that this method is superior to a similar method using ether. The method gives correct or slightly high results for roots containing over 0.5 per cent rotenone. For roots containing 0.3 per cent rotenone or less the method is without value unless larger samples are used. Acetone gives a more rapid extraction of the rotenone, but its complete separation from such extracts is difficult. Values based on the optical rotation of the extracts are incorrect. A purely chemical method for the accurate determination of rotenone in plant materials is needed. LITERATURE CITED (1) Clark, J . Am. C h m . Soc., 52, 2461-64 (1930). (2) Clark, Ibid., 53, 313-17 (1931).
(3) (4) (5) (6) (7)
VOl. 5, No. 1
Clark, Ibid., 53, 729-32 (1931). Darley, J . Econ. Entomol., 24, 111-15 (1931). Davidson, Ibid., 23, 868-74 (1930). Davidson, Ibid., 23, 877-79 (1930). Fryer, Stenton, Tattersfield, and Roach, Ann. Appl. Biol., 10,
18-34 (1923). (8) Georgi, Malayan Agr. J., 17, 361-63 (1929). (9) Georgi and Curtler, Ibid., 17, 326-34 (1929). (10) Jones, J. Am. Chem. Soc., 53, 273-1 (1931). (11) Jones and Smith, Ibid., 52, 2554-02 (1930). (12) Roark, Soap, 7, 97, 99, 101 (1931). (13) Shepard and Campbell, J. Econ. Entomol., 25, 1 4 2 4 4 (1932). (14) Tattersfield and Roach, Ann. A p p l . B i d , 10 1-17 (1923). RECEIVED August 30, 1932.
New Reagent for Deterrnination of Zinc ARMAND J. QUICK Cornel1 University Medical College, New York, N. Y.
Z
INC is readily precipitated from an acid or a neutral solution by means of borneolglycuronic acid. Since this acid does not form insoluble salts with the other common metals, except cadmium, it offers an easy method not only for detecting zinc, but also for separating it from a mixture of other cations. Zinc in as low a concentration as 0.03 per cent will give a characteristic crystalline precipitate when treated with a 5 per cent aqueous solution of borneolglycuronic acid. Zinc borneolglycuronate is a white glistening salt containing 2 molecules of water of crystallization. Andusis. Calculated for (C16H2601)2Zn.2H?O: glycuronic acid, 51.1. Found: 50.8, 51.5.
The development of a simple and satisfactory quantitative method for zinc based on the precipitation of zinc borneolglycuronate is feasible and promising. The precipitate can be weighed directly, or it can be hydrolyzed by boiling with 1.0 N hydrochloric acid for 15 minutes. I n this procedure, borneolglycuronic acid is split, and the glycuronic acid thus liberated can be determined by any of the common sugar methods, of which the Shaffer-Hartmann (2) is especially satisfactory From the determined glycuronic acid, zinc can be calculated. The reagent, borneolglycuronic acid, is best prepared by the method described by the writer (1). For the convenience of the reader, the essential details of the method are again outlined: Five grams of pulverized borneol are fed to a dog. The drug can be mixed directly with the food. The urine is collected for 24 hours, acidified, and treated with excess lead acetate to remove pigments. The precipitate is filtered off, and the filtrate heated to boiling. An excess of zinc acetate solution is added, and the precipitated zinc borneolglycuronate filtered off and washed with hot water until all coloring matter has been extracted. To prepare borneolglycuronic acid, 100 grams of the zinc salt are dissolved in 140 cc. of hot 3.5 N sulfuric acid. The solution is rapidly cooled in ice and allowed to stand for several hours. The crystalline borneolglycuronic acid is filtered off and washed with cold water. One recrystallization from hot water is necessary to obtain a pure product. LITERATURE CITED (1) Quick, A. J., J . Biol. Chem., 74, 331 (1927). (2) Shaffer. P., and Hartmann, A., Ibid., 45, 365 (1920-21). RECEIVED August 2, 1932.
