Several investigations in this laboratory have shown that color tests for the various alkaloids are not specific lss. In testing a large number of organic compounds, it was found that many compounds might give the same characteristic color tests as given by various alkaloids such as atropine, morphine, or strychnine.
The present research deals with the Murexide test for caffeine and theobromine. When a substance such as caffeine is treated with an oxidizing agent and evaporated to dryness, a beautiful, brilliant purplish pir,k color appears when the residue is exposed to ammonia vapors.
No record could be found in the literature inr which a large number of various organic compounds had been subjected to the Murexide test. The object, therefore, of the investigation reported in this publication was to test a large number of organic compounds with the Murexide test in order to determine whether or not there was any great number of substances which would give this test, and whether this test was characteristic of any given class of organic compounds. Also, these different organic compounds were mixed in varying amounts with caffeine, and the test applied in order to determine which substances would interfere with the characteristic reaction. AUTENRIETH'J~~~O~~S that xanthine, x,7-monomethyl xanthine, and paraxanthine give a positive Murexide test. FULLER' states that theophylline likewise gives a positive test. VITALI* adds uric acid to the list of substances giving the test. HURTLEY~ claims a positive test for tyrosine, tryptophane, cystine, and glucosamine. Procedzlre of t&s. Three tests were made on each organic compound. For the first test, IO mg of the compound were treated with I ml of concentrated hydrochloric acid and IOO mg of potassium chlorate and evaporated to dryness on the steam bath. The residue was exposed to ammonia vapors. In the second test, IO mg of the given compound and IO mg of caffeine were treated in the same manner. In the third test, 50 mg of the compound and IO mg of caffeine were subjected to the same test. References p. rao.
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