Mutual diffusion in solutions of alkali metal halides Aqueous LiF, NaF and KF at 25 °C

Abstract

A Taylor dispersion tube has been used to measure mutual diffusion coefficients (interdiffusion coefficients) for binary aqueous solutions of LiF (from 0.002 to 0.050 mol dm⁻³), NaF (0.002 to 0.900 mol dm⁻³) and KF (0.002 to 8.00 mol dm⁻³) at 25 °C. The Taylor results together with previously reported activity and density data are used to evaluate resistance coefficients for the mutual diffusion of aqueous NaF and KF. Diffusion coefficients, resistance coefficients and relative viscosities of the fluoride solutions are compared with the corresponding quantities for aqueous solutions of LiCl, LiBr, NaF, NaCl, NaBr, NaI, KCl, KBr, KI, RbCl and CsCl. In contrast to the resistance coefficients of aqueous KCl, KBr, KI, RbCl and CsCl solutions which are relatively insensitive to changes in composition, the resistance coefficients of concentrated LiCl, LiBr, NaCl, NaBr, NaI and KF solutions increase sharply with increasing salt concentration as a consequence of the higher viscosities of these solutions.