Determination of Au(III) in the surface layers formed anodically on the gold electrode

Layers of surface compounds were anodically formed on a gold electrode in 0.5 M NaHSO4 solution. The amount of Au(III) was determined photometrically following the dissolution of these layers in 0.1 M HCl solution. It has been determined that the amount of Au(III) is directly proportional to the amount of charge required for reduction of surface compounds. The proportionality coefficient was evaluated to be 0.53 +/- 15% mg C-1. It is similar to 20% less than the theoretical value of the electrochemical equivalent in the cathodic reduction of Au3+ ions. Interaction between Au(III) and metallic gold, occurring during the conversion of surface compounds into AuCl4- and resulting in AuCl2- formation, is considered to be one of the reasons responsible for the losses of Au(III). The possibility of the gold ionisation in the monolayer formation region, i.e., up to E = 1.4 V-1.5 V (Ag\AgCl), has been experimentally substantiated. (C) 1998 Elsevier Science S.A.