Origin. - Obtained by distilling a solution of potassium ferrocyanide acidulated with sulphuric acid, the distillate passing into a receiver containing a solution of silver nitrate. The process should be continued until the distillate no longer produces a precipitate in the receiver. The precipitate is finally washed with distilled water and dried. It should contain not less than 99.9 per cent. of pure silver cyanide, corresponding to 80.48 per cent. of metallic silver.

Description and Properties. - A white powder, without odor or taste; permanent in dry air, but gradually turning brown on exposure to light. Insoluble in water, alcohol, or cold nitric acid; soluble in boiling nitric acid, ammonia water, and solution of sodium hyposulphite or potassium cyanide. It should be kept in dark, amber-colored vials, protected from light. Not used internally.