Cyanides

Cyanides, a class of substances which may be regarded as derived from hydrocyanic or prussic acid, HCN, by the substitution of other elements, or "radicals," for the hydrogen. Of the metallic cyanides, potassium salt, KCN, is of great importance industrially, being largely employed in photography and electro-plating. It also finds constant application in metallurgical and chemical operations. The metallic cyanides are all poisonous, some being as strong as prussic acid itself. Cyanides may be detected by heating with yellow ammonium sulphide, and adding a ferric salt to a drop of the distillate, when a fine blod red coloration results. A large number of "double cyanides" exist - i.e. compounds in which two metals are present, as e.g. potassium ferrocyanide (prussiate of potash). The organic cyanides (ethyl cyanide, etc.) have the same composition as the Carbamines (q.v.), the difference in their substances being explained by the supposition that their constitution is as indicated by the formulae: XCN, cyanides; XNC, carbamines.