Electromigration and self-diffusion in ionic melts

Abstract

An experimental technique is described for glass-fibre-paper electrophoresis and diffusion experiments with radio-active tracers in fused salts. It has been found that for the system NaNO₃+KNO₃ the ionic mobility of NO^–₃ is independent of composition, while the ionic mobilities of Na⁺ and K⁺ decrease when going from NaNO₃ to KNO₃ in such a way that in NaNO₃, Na⁺ is moving faster than K⁺, and in KNO₃ K⁺ is the faster moving ion.

The diffusion coefficients of Na⁺ and of K⁺ also decrease from NaNO₃ to KNO₃, but the former always remains larger than the latter one. Cationic and anionic transport numbers tend to become equal if the temperature is raised. There is no linear dependence of the logarithm of the ionic mobilities and the diffusion coefficients as a function of the reciprocal absolute temperature. The Nernst-Einstein parameter is always less than unity.