4023. Tests for Distinguishing Alkaloids

4023.    Tests for Distinguishing Alkaloids. Perchloride of gold is a decisive test of certain vegetable alkalies. The following are the colors of the precipitates which it produces with the salts of the annexed alkalies dissolved in water; quinine, buff-colored; cinchonine, sulphur-yellow; morphine, yellow, then bluish, and lastly, violet; in this last state the gold is reduced, and the precipitate is insoluble in water, alcohol, the caustic alkalies, and sulphuric, nitric, or hydrochloric acids; brucine, milk, coffee, and then chocolate-brown ; strychnine, canary-yellow; vara-trine, slightly greenish-yellow. All these precipitates, with the exception mentioned, are very soluble in alcohol, insoluble in ether, and slightly soluble in water. Among the reactions of chloride of gold, there are two which appear to be especially important: they are those which occur with morphine and brucine; these are sufficiently marked to prevent these alkalies from being mistaken for each other, and also yield pretty good characteristics for distinguishing brucine from strychnine.

4024. Alkaloids Detected by Picric Acid

4024.    Alkaloids Detected by Picric Acid. Hager has found that this acid precipitates various alkaloids from their solutions, such as brucine, strychnine, veratrine, quinine, cinchonine, and some alkaloids of opium. Morphine and atropine, however, are precipitated only from neutral and concentrated solutions, and the precipitate dissolves pretty easily in water. Glucosides, casein, and pseudo-morphine resist the action of the picric acid.

4025. Quinometry

4025.      Quinometry. The method of estimating the quantity of quinine in cinchona bark and the salts obtained from it. • Tho following tests give very accurate results in examining the bark; and the salts are tested in the same way, but the result is not quite so accurate, as it includes any quinidine (see No. 4028 (Quinidine)) that may be present in the quinine; and makes, therefore, the apparent richness of the sample greater than it really is. (Cooley.)

4026. Test for the Strength of Quinine

4026.    Test for the Strength of Quinine. Make a decoction of 100 grains of bark in 2 fluid ounces distilled water; filter, and precipitate with a sufficient quantity of a concentrated solution of carbonate of soda. Heat the fluid until the precipitate is dissolved; and when cold, dry and weigh it. It should weigh 2 grains or more, and dissolve entirely in a solution of oxalic acid. To render tho result strictly accurate, the bark should bo exhausted with ether, and the mixed solutions evaporated. Salts of quinine may be tested in the same manner. (Cooley.)

4027. Test for the Percentage of Quinine in Bark, etc.

4027.     Test for the Percentage of Quinine in Bark, etc.. Exhaust 100 grains of bark with acidulated water; filter the solution, and render it alkaline with liquor of potassa; next agitate it with about 1/3 its volume of chloroform, and allow it to repose a short time; the chloroform, holding the alkaloid in solution, sinks to the bottom of tho vessel in a distinct stratum, from which tho supernatant liquid must be separated by decantation; the chloroformic solution, either at once or after being washed with a little cold water, is allowed to evaporate, and the weight of the residuum in grains gives the percentage of richness of the sample. Ether may be used instead of chloroform, but the ethereal solution will form the upper stratum instead of the lower. This test is also applicable to the salts of quinine, but with restrictions referred to in No. 4025. (Rebourdain.)