ELECTROCHEMICAL STUDIES ON THE MECHANISMOF GOLD DISSOLUTION IN THIOSULFATE SOLUTIONS
(InStdute of Chrmicof Meuulargy; Lvhinere Acadeiny of Sciences; Beijing100080; China)
Abstract: The dissolution of gold in aqueous thiosulfate solution and the effect of the presence of am-monia in the solution were investigated with methods of voltammetry and electrochemicalimpedance spectra(EIS). Results indicated that the anixlic voltummetric curves of the gold elec-trode in thiosulfate solutions does not indicate the features of gold dissolution. The passive phe-nomena of sold may result from the elemental sulfur adsorbed on the gold surface due to the sur-face decomposition of or the S2O32- electrochemical oxidation of S2- on the electrede surface. Byaddition of ammonia into the system, the passivation of gold is completely eliminated, and thegold dissolution, on the other hand, seems to be eatalyzed through the formation of the interme-dia complex Au(NH3)2+.
Key words: gold disaolution thiosulfafe solution mechanism electrochemistry