Vapor pressure measurements on non-aqueous electrolyte solutions. Part 2. Tetraalkylammonium salts in methanol. Activity coefficients of various 1-1 electrolytes at high concentrations

Abstract

Precise vapor pressure data for solutions of Et4NBr, Bu4NBr, Bu4Nl, Bu4NClO4, and Am4NBr in methanol at 25°C in the concentration range 0.04<m[mol-(kg of solvent)−1]<1.6 are communicated and discussed. Polynomials in molalities are given which may be used for calculating precise vapor pressure depressions of these solutions. Osmotic coefficients are calculated by taking into account the second virial coefficient of methanol vapor. Discussion of the data at low concentrations is based on the chemical model of electrolyte solutions taking into account non-coulombic interactions; ion-pair association constants are compared to those of conductance measurements. Pitzer equations are used to reproduce osmotic and activity coefficients at high concentrations; the set of Pitzer parameters b=3.2, α1 = 2.0, and α2 = 20.0 is proposed for methanol solutions.