THE DISSOLUTION BEHAVIOR OF SILVER IN AMMONIACAL SOLUTIONS WITH CUPRIC AMMINE

The dissolution behavior of silver in ammoniacal solutions with cupric ammine as an oxidant has been investigated using a rotating disk electrode. The rates of dissolution of silver were determined by an electrochemical means as well as a direct measurement of silver ions reported in the bulk solution as a function of time. The variables investigated included stirring speed, temperature, concentration of lixiviants, and pH of the solutions. The rate of dissolution under the conditions studied was controlled by an electrochemical reaction at the liquid/solid interface with an apparent activation energy of 48.07 kJ/mol. The rate was a half order with respect to the concentration of cupric tetra-ammine, Cu(NH3)4(2+). The results are explained in terms of a mixed potential theory.