Note H — II. DETECTION OF POISONS, THE PRESENCE OF WHICH IS SUSPECTED.

Ferrocyanides and ferricyanides—non-poisonous compounds—likewise, evolve hydrocyanic acid when distilled with a strong acid. Their presence is indicated by stirring a small portion of the materials with water, filtering the fluid, acidulating the filtrate with hydrochloric acid, and testing two portions: one with sesquichloride of iron, the other with protosulphate of iron. If either of the above salts be present, a blue precipitate is produced.—Trans.