_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. CARBONIC ACID FAILS TO DISSOLVE THE ALKALOID. After the evaporation is completed, ether is added to the watch-glass: the alkaloid may, or may not, be dissolved. The ether is then evaporated at the ordinary temperature of the air. _Ether fails to dissolve the alkaloid._ It probably consists of _berberine_. In this case, it will possess a yellow color, and its hydrochlorate will give a reddish-brown precipitate upon addition of sulphide of ammonia. _Ether dissolves the alkaloid._--A small portion is treated with nitric acid. If an intense green coloration is produced, the remaining portion is dissolved in ether, and an ethereal solution of oxalic acid added. If the precipitate now formed does not dissolve upon the addition of a little water, there is reason to suppose the presence of _aricine_. Provided the addition of nitric acid did not produce a coloration, the mixture of the alkaloid and this acid is treated with a small quantity of sulphuric acid: if the fluid now acquires a red color, the substance probably consists of _narcotine_.