Investigations on silver sulfide

Abstract

The variability of the Ag/S ratio in silver sulfide has been studied with the help of electrochemical measurements. Silver sulfide coexisting with metallic silver at 200°C contains a silver excess of 2.0×10 -3 g-atom Ag/mole Ag2S, whereas silver sulfide coexisting with liquid sulfur has very nearly ideal stoichiometric composition. The variability of the Ag/S ratio in βAg2S at 160°C is of the order of 3×10-6 g-atom Ag/mole Ag2S. The interdiffusion coefficient of silver in Ag2S at 220°C is about 3×103 times greater than the self-diffusion coefficient of silver in Ag2S. A thermodynamic calculation gives the result that the transformation temperature of Ag2S coexisting with metallic silver is about 1.7°C lower than the transformation temperature of Ag2S coexisting with liquid sulfur in accordance with observations made by Kracek.