=Chloride of gold= forms with the alkaloids compounds, many of which are crystalline, and most admit of utilisation for quantitative determinations. Chloride of gold does not precipitate amides or ammonium compounds, and on this account its value is great. The precipitates are yellow, and after a while are partly decomposed, when the colour is of a reddish-brown. =Platinic chloride= also forms precipitates with most of the alkaloids, but since it also precipitates ammonia and potassic salts, it is inferior to gold chloride in utility. § 303. (1.) =Phosphomolybdic Acid as a Reagent for Alkaloids.=--_Preparation_; Molybdate of ammonia is precipitated by phosphate of soda; and the well-washed yellow precipitate is suspended in water and warmed with carbonate of soda, until it is entirely dissolved. This solution is evaporated to dryness, and the ammonia fully expelled by heating. If the molybdic acid is fairly reduced by this means, it is to be moistened by nitric acid, and the heating repeated. The now dry residue is warmed with water, nitric acid added to strong acid reaction, and the mixture diluted with water, so that 10 parts of the solution contain 1 of the dry salt. The precipitates of the alkaloids are as follows:-- Aniline, Bright-yellow, flocculent. Morphine, „ „ Narcotine, Brownish-yellow, „ Quinine, Whitish-yellow, „ Cinchonine, „ „ Codeine, Brownish-yellow, voluminous. Strychnine, White-yellow, „ Brucine, Yelk-yellow, flocculent. Veratrine, Bright-yellow, „ Jervine, „ „ Aconitine, „ „ Emetine, „ „ Theine, Bright-yellow, voluminous. Theobromine, „ „ Solanine, Citron-yellow, pulverulent. Atropine, Bright-yellow, flocculent. Hyoscyamine, „ „ Colchicine, Orange-yellow, „ Delphinine, Grey-yellow, voluminous. Berberine, Dirty-yellow, flocculent. Coniine, Bright-yellow, voluminous. Nicotine, „ „ Piperine, Brownish-yellow, flocculent.