Kinetics of silver dissolution in sulfide containing thiocarbamide electrolytes

Effective values of reaction order with respect to ligand P, transfer coefficient alpha, and exchange current i(0) at constant silver surface coverages theta by sulfide ions are measured. The employed solutions contained from 0.4 to 0.05 M thiocarbamide, 0.5 M HClO4, 10(-4) M AgNO3, and from 10(-5) to 10(-4) M Na2S. It is shown that the exchange current grows approximately linearly from 10(-5) to 1.5 x 10(-4) A/cm(2) at theta increase in the range from zero to 0.8, while alpha and P values grow negligibly in the ranges of 0.4-0.45 and 0.9-1.1, accordingly. The obtained results are compared with the data of similar studies of the gold behavior in acidic thiocarbamide solutions. The possible reasons for the different effects of sulfide ion chemisorption on the anodic dissolution of gold and silver in the studied solutions are discussed.