ELECTROCHEMICAL REDUCTION OF SILVER THIOSULFATE COMPLEXES .1. THERMODYNAMIC ASPECTS OF SOLUTION COMPOSITION

Deposition of silver from electrolyte solutions is of major importance in the industrial applications of photographic development and electr oplating. Prior to the kinetic study of the reduction of silver thiosu lphate complexes, the concentrations, activities and activity coeffici ents of all components formed in AgNO3-Na2S2O3-NaNO3 solutions are cal culated, starting from the measurement of the equilibrium potential. I n view of the high ionic strength of the solutions (greater than 0.1 m ol kg-1), the ion interaction model is applied for the estimation of t he activity coefficients, inevitably imposing the use of an iterative calculation routine. The activity coefficients are shown to comply wit h known thermodynamic laws, supporting the appropriateness of the mode l, together with the approximations.