INVESTIGATION OF GOLD OXIDATION IN SULFURIC MEDIUM .2. ELECTROGRAVIMETRIC TRANSFER-FUNCTION TECHNIQUE

Gold oxidation in sulphuric medium was investigated in a previous paper by using electrochemical impedance techniques. The experimental results were compared to those obtained by means of cyclic voltammetry. It was shown that gold oxidation occurs in three monoelectronic steps in sulphuric medium. Usual impedance techniques gave informations on the number of elementary steps, on the number of adsorbed intermediates and an estimation of some rate constants through a fitting procedure by using a model of the reaction mechanism. In order to obtain complementary information on the interfacial phenomena, a quartz microbalance in quasi-steady-state and in sinusoidal regime was used in this study to reach new data about mass changes at the electrode. The results confirm the proposed three monoelectronic step model and give some informations on the molar weight of the chemical species involved in the reaction mechanism.