A kinetic study of the silver-mercury contact reaction

Abstract

The solid-liquid diffusion couple technique was employed to determine the interdiffusion coefficient of the gamma phase in the Ag-Hg contact reaction. Diffusion coefficients were calculated with the aid of an equation given by Wagner. The composition range of the gamma phase was determined to be between 55.3 and 57.5 at% by electron microprobe analysis, and values for the average interdiffusion coefficient of the gamma phase were found to beD _av(cm²sec⁻¹)=3.181×10⁻⁵exp (−32539 (J mol⁻¹)/RT) in the temperature range 40 to 115° C. The amalgamation reaction between silver and liquid mercury proceeded with the formation of gamma phase and a solid solution of Ag-Hg. The growth of gamma phase followed a parabolic rate law. The penetration of liquid mercury into grain boundary of the gamma phase caused the gamma to be crumbled off. The possibility of short-circuit diffusion is discussed.