ELECTROCHEMICAL STUDIES ON THE MECHANISM OF GOLD DISSOLUTION IN THIOSULFATE SOLUTIONS

ＥＬＥＣＴＲＯＣＨＥＭＩＣＡＬＳＴＵＤＩＥＳＯＮＴＨＥＭＥＣＨＡＮＩＳＭＯＦＧＯＬＤＤＩＳＳＯＬＵＴＩＯＮＩＮＴＨＩＯＳＵＬＦＡＴＥＳＯＬＵＴＩＯＮＳＺｈｕ，Ｇｕｏｃａｉ；Ｆａｎｇ，Ｚｈａｏｈｅｎｇ；Ｃｈｅｎ，Ｊｉａｙｏｎｇ（ＩｎＳｔｄｕｔｅｏｆＣｈ...

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 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