a. It dissolves completely; absence of strychnia; probable presence of Brucia, Quina (?), or Veratria:—the alcoholic solution is evaporated to dryness, and, if quina has been already detected, the residue is divided into two portions, one of which is tested for Brucia, the other for Veratria.
b. It does not dissolve, or not completely; probable presence of Strychnia, and perhaps also of Brucia and Veratria:—the filtered fluid is divided into two portions, and tested separately as at a.
4. The original liquid 1. a. may contain Salicine, a proximate vegetable principle closely allied to the alkaloids:—a portion is boiled with hydrochloric acid for some time; the formation of a precipitate shows the presence of Salicin. (See 2, below.)[25]
[25] For further information on this subject, see the admirable ‘System of Qual. Chem. Anal.,’ by Dr C. R. Fresenius. Churchill.
II. (Larocque and Thibierge.) Terchloride of gold is recommended, by these writers, as a more decisive test for the alkaloids than the ‘double chloride of gold and sodium’ commonly employed for this purpose. The following are the colours of the precipitates which it produces with the aqueous solution of their salts:—Brucia, milk-brown, passing into coffee-brown, and lastly chocolate-brown:—CINCHONIA, sulphur yellow:—MORPHIA, 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, and hydrochloric acid; it forms with aqua regia a solution
which is precipitated by protosulphate of iron:—QUINA, buff-coloured:—STRYCHNIA, canary-yellow:—VERATRIA, pale greenish-yellow. All these precipitates, with the exception mentioned, are very soluble in alcohol, insoluble in ether, and only slightly soluble in water. Those with morphia and brucia are sufficiently marked to prevent these alkalies from being mistaken for each other; and those with brucia and strychnia are, in like manner, easily distinguishable.
III.—Mr Wanklyn discriminates the different alkaloids from the estimation of the ammonia they evolve. His process is as follows:—A small flask with a lateral tube, and connected with a Liebig’s condenser, is charged with about 25 c. c. of an alkaline solution of permanganate potash made by dissolving 200 grammes of caustic potash and 8 grammes of crystallised permanganate of potash in 1 litre of water. A minute quantity of the alkaloid carefully and accurately weighed is now introduced, and the mixture slowly distilled. The most satisfactory results are obtained by treating from 1 to 5 milligrammes of the alkaloid in this way, but quantities so small as 1⁄10th of a milligram will in skilled hands give accurate results. The ammonia is formed in the distillate by Nesslerising it, as described under Water analysis. For all practical purposes the poisonous alkaloids may be divided into four classes:
(a) Those which yield from 5 to 2 per cent. of ammonia.
(b) Those which yield from 2 to 3 per cent. of ammonia.
(c) Those which yield from 3 to 5 per cent. of ammonia.