THE ALKALOID IS VOLATILE.
In this case it may consist of nicotine, conine or aniline: less known alkaloids (piccoline, etc.) may also be present. We will confine ourselves to the consideration of the three first mentioned.
The alkaloid is divided into several portions which are placed on watch-glasses and submitted to the following tests:
a. A drop is treated with nitric acid: this may, or may not, impart a red tint to the alkaloid; if it does, another drop is treated with dry hydrochloric acid gas: if it assumes a deep violet color, it probably consists of conine.
b. In case a red color was not produced by the addition of nitric acid, another drop is treated with chloride of lime. If it acquires a violet tint, and two other drops, when heated, one with arsenic acid, the other with nitrate of mercury, become red, the body present consists of aniline.
or an homologous base.
c. Should the above tests fail to give positive results, and the substance, when treated with chlorine, assumes a blood-red color, and with hydrochloric acid does not change in the cold but turns to a deep violet color upon boiling, it probably consists of nicotine.
THE ALKALOID IS FIXED.
A very minute quantity is dissolved in the smallest possible amount of hydrochloric acid, and an excess of ammonia added. Three cases are now possible: (a) A precipitate, insoluble in an excess of the precipitant, is immediately formed; (b) a precipitate is formed, which, at first dissolves, but is subsequently deposited from the fluid; (c) no precipitate is produced, or, in case one forms, it dissolves in an excess of the precipitant and fails to separate out upon allowing the fluid to stand.
a. Ammonia produces a permanent precipitate.
A small quantity of an aqueous solution of carbonic acid is poured over the alkaloid in the water-glass, and notice taken whether it dissolves or not: in either case the mixture is evaporated on a water-bath to dryness, in order to avoid a loss of substance.