On Gold(I) Complexes and Anodic Gold Dissolution in Sulfite-Thiourea Solutions

摘要

Processes involving gold(I) complexes were studied in sulfite-thiourea (TU) solutions. It is shown that at pH > 5 the complex [] undergoes irreversible decomposition followed by deprotonation and formation of a solid phase. From the data of pH in mixed solutions, the equilibrium constants were evaluated: , log(10) beta (1) = -1.2, log(10) beta (2) = -3.6. Some aspects of the anodic dissolution of gold in mixed sulfite-thiourea solutions are considered. With the help of the carbonate buffer system the change of the anodic current density j (a) was studied at high pH; j (a) (pH) has a maximum at pH 11.6-11.9 for E (a) = 0.3-0.6 V (vs. NHE). At pH > 12.0, the j (a) values decrease sharply. Possible mechanisms of anodic gold dissolution, as well as the role of sulfite, are discussed.