Characters. - A white powder permanent in dry air, but gradually turning brown on exposure to light, odourless and tasteless.

Solubility. - It is insoluble in water or alcohol; insoluble in cold, but soluble in boiling nitric acid, with evolution of hydrocyanic acid; also soluble in water of ammonia and in solution of hyposulphite of sodium.

Reactions. - When heated the salt fuses, gives off cyanogen gas, and on ignition metallic silver is left.

Officinal Preparation. u.s.p. Acidum Hydrocyanicum Dilutum.