Cyanide

Cyanide refers to a family of chemical species that contain the cyano group CN−, including hydrogen cyanide (HCN) gas and metal cyanide salts such as sodium cyanide (NaCN) and potassium cyanide (KCN). Organic nitriles (R-CN) are closely related but distinct from cyanides themselves. In aqueous solution at physiological pH, cyanide exists mainly as CN− and an equilibrium with HCN.

Cyanide is highly toxic to humans and many other organisms. It inhibits mitochondrial respiration by binding to cytochrome c oxidase, producing histotoxic hypoxia. Toxic effects depend on dose and route of exposure and can include headache, confusion, seizures, cardiovascular collapse, and death. Hydrogen cyanide is a volatile, colorless to pale blue liquid with an almond-like odor for some individuals, though olfactory detection is unreliable at toxic levels.

Sources and production: cyanides occur naturally in trace amounts in some seeds and fruit pits (for example, apricot kernels and bitter almonds) and can be produced industrially by several processes, including the Andrussow process for hydrogen cyanide. Cyanides are used in mining, electroplating, organic synthesis, and as fumigants.

Applications: in mining, cyanide leaching dissolves gold and silver from ore via formation of soluble dicyano metal complexes. In organic chemistry, cyanide acts as a nucleophile in various reactions. Cyanides are also used in electroplating and as precursors to many nitrile compounds.

Safety and regulation: due to acute toxicity and environmental hazards, cyanides are subject to strict handling, storage, and disposal regulations. Antidotes include hydroxocobalamin and the nitrite-thiosulfate combination, administered as part of emergency treatment. Environmental releases require rapid containment and oxidation or other treatment to convert cyanide to less toxic forms.