The Anodic Dissolution of Gold in Cyanide Solutions

The anodic dissolution of gold in alkaline cyanide solutions has been studied by potentiostatic and galvanostatic techniques under high‐purity conditions. Measurements were made at room temperature and in the p H range 11–13, the concentration varying from 0.05 to 0.50%. The results show that gold has three current maxima in the potentiostatic curve at −0.6, +0.1, and 0.4v vs. . The first and last are p H dependent, but that at +0.1v is not. The rate‐determining step in the active region (more cathodic than −0.6v) is interpreted as the reaction , occurring at a low coverage of adsorbed species. The passive states at −0.6v and +0.1v are considered to arise from basic cyanide films, while auric oxide is formed at +0.4v. The change in reflectivity of the gold surface at constant potential has indicated that the three regions of passivity can be associated with surface films.