COCAINE 691 2. Giesel's Test.—A solution of potassium permanganate gives a fine, bright, violet precipitate, which shows rhombic crystals arranged in rosettes when seen under the microscope. Fig. 188.—Microphotograph of Cocaine crystals X 200. (R.B. Dr. K. N. Bagchi.) (Obtained by Harikin's test.) Fig. 189.—-Microphotograph of Cocaine crystals X 200. (K.B. Dr. K. N. Bagchi.) (Obtained by Bagcbi's modified method of Hankin's test) 3. Nankin's Test, — Cocaine is dissolved in a saturated or semi-saturated solution of alum. A drop of potassium permanganate solution is spread out, and dried on a glass slide. A drop of the alum solution is placed in the permanganate film and covered with a cover-slip. The characteristic cry- stals of permanganate of cocaine form almost immediately. Under the microscope these crystals are seen to be rectangular in shape and pale pink in colour. This test is of such delicacy that it can be used to reveal the presence of cocaine on a small piece of paper in which this substance has been wrapped. similar but easily distinguishable crystals are also formed by Alypin, Tropa- cocaine, and Scopolamine. No crystal? are formed by Beta-eucaine, Stovaine, Novocaine, Holocaine, and Nirvanine.48 Antipyrin which is often mixed with cocaine interferes with the test and should be removed. The powder should, therefore, be dissolved in water and ammonia added to it, when cocaine would be precipitated. This should then be filtered and the residue should be tested. Dr. Bagchi, Chemical Examiner to the Government of Bengal, adopted the following modification in the method of this test : — If a trace of cocaine or cocaine hydrochloride is dissolved in a few drops of a saturated solution of alum and a small drop of this solution is added to a drop of a saturated solution of potassium permanganate on a microscopic slide and the two are mixed together by gently rubbing on the slide for about a minute or two and then covered with a cover-slip and examined under the microscope, small characteristic crystals of cocaine permanganate are seen. 43. UP. Chem, Exam. Annual Hep., 19U; Analyst, Jan, 1911, Vol. XXXVI, p. 2.