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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.