On diffusion of metals in mercury

Abstract

The method of determination of diffusion coefficients of metal in Hg was studied again. The effect of the radius of the amalgam electrode on the experimental results of diffusion coefficients was investigated. The diffusion coefficients of metal in Hg are independent of the concentrations of amalgams. Diffusion of metals in complex amalgams was investigated. When there is no interaction of metals in a complex amalgam, the diffusion will not be affected by the existence of other components. When interaction of components exists, with the formation of only a small quantity of insoluble intermetallic compounds, the diffusion will not be markedly affected, but the concentration of the metal in liquid phase will be reduced. The linearity of the i vs. t −1/2 plot will be broken in the case of formation of a large quantity of insoluble intermetallic compounds. Pt dissolved in Hg affects the determination of diffusion coefficients of Zn and Tl. The relation between diffusion coefficients of metals in Hg and atomic radii was further examined. Diffusion of metals in Hg satisfactorily obeys the Einstein-Sutherland equation ( n≈4) where the “effective radii” of diffusing particles should be used instead of the atomic radii. The i-t −1/2 plot used by Kao and Chang and the it 1/2− t 1/2 plot used by Stevens and Shain were compared. These two plots are intrinsically identical and give mutually agreeing results, but the i-t −1/2 plot is simpler to use.