Continued from page 212.) SPECIAL METHODS. ACETANILIDUM.-The melting points of good products may range between 112" and 115O. Chemical authorities give figures varying from 112O to 116" for the pure substance. A boiling point determination is not required as a test of purity. The U. S. P. requirements regarding inorganic impurities are somewhat vague; foreign pharmcopaeias allow limits of 0.05 to 0.1 per cent; products containing not more than 0.05 per cent. of non-volatile matter are readily

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... tainable. ACEToNuM.-The tests and physical constants given cannot be entirely relied upon to determine if a given sample contain the required percentage of absolute acetone, because of the probable presence of small amounts of methyl alcohol. Messinger's method is generally regarded t o be the most reliable for an assay, although it includes any "acetone oils" that may be present also, but these, when present in considerable quantity, are detected by a raised boiling point. The details may be conveniently carried out as follows: About 2 gm. of acetone are weighed in a stoppered weighing-bottle containing about 10 cc. of water, then diluted with water to 1 liter. Of this solution, 20 cc. are mixed with 25 cc. of n/l sodium hydroxide in a 250 cc. glass-stoppered flask, 50 cc. of n/10 iodine added, and the mixture allowed to stand 15 minutes. It is then acidulated with about 25 cc. of n/l hydrochloric acid and the liberated excess of iodine titrated with n/10 sodium thiosulphate. Each cc. of n/10 iodine (0=16) consumed in the formation of iodoform corresponds to 0.0009675 gm. of acetone. A blank test should be made with the reagents and any iodine consumed deducted from that consumed in the determination. The U. S. P. boiling point applies to normal barometric pressure only. Since glass loses weight during contact with steam and hot water, platinum and well-glazed porcelain dishes are preferable for determining the non-volatile matter. ACETPHENETIDINUM.-A melting point interval of 134" to 135" is slightly narrow, as satisfactory products often begin to melt at about 1 3 3 O . Non-volatile matter should not exceed 0.05 per cent. In the bromine test for acetanilide, the bromine water should be added drop by drop, with agitation after each addition, until the solution is permanently yellow. In case a considerable amount of bromine water is added all at once, a turbidity or precipitate is liable to form with pure acetphenetidin. The second test for acetanilide is superfluous ; it has been found faulty and misleading by various analysts. The test for paraphenetidin may fail to show presence of traces of this unless a control test is made with a sample of known purity and the resulting colors compared. The delicacy of the test may be increased by boiling 1 gm. of acetphenetidin, 3 cc. of *Analytical Laboratory of Powers-Weightman-Rosengarten Company.