Solvation effects on the conductivity of concentrated electrolyte solutions

Abstract

The Falkenhagen–Leist–Kelbg equation for the conductivity of electrolyte solutions has been extended to include the effect of solvation on the concentration of the salt. Two equations have been derived, both of which have only two freely adjustable parameters at any temperature: Λ0 the molar conductance of the salt at infinite dilution and H0, a solvation number parameter for the salt. In one of these equations H0 is assumed to be independent of concentration. In the other, H0 is assumed to be dependent on concentration and an explicit concentration dependent formula is derived for H0. Conductance data for the alkali halide salts in the 0.5 to 10 m concentration range and 0 to 60 °C temperature range were found to be adequately reproduced by both these equations, but with the variable hydration parameter equation yielding better fits to the data. The H0 parameters from the fixed hydration parameter equation are found to be similar to those obtained from the analysis of activity coefficient and other data whereas the variable hydration parameter equation yields H0 parameters which are much larger.