The chemical reaction for the dissolution of gold, the "Elsner equation", follows:
: 4Au + 8NaCN + O + 2HO → 4Na[Au(CN)] + 4NaOH
Potassium cyanide and calcium cyanide are sometimes used in place of sodium cyanide.
Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen. The soluble gold species is dicyanoaurate. from which it can be recovered by adsorption onto activated carbon.