Activity Coefficients in Quaternary Systems at 298.15 K: RbCl + MeOH + EtOH + H2O and CsCl + MeOH + EtOH + H2O Systems

Abstract

Activity coefficients of RbCl or CsCl in methanol + ethanol + water were determined at 298.15 K by the cells containing ion-selective electrodes (ISEs). The molalities of RbCl and CsCl are up to approximately 1 mol·kg–1 in the mixed solvents, and the mass fractions of five aqueous MeOH/EtOH mixtures studied were (5/5, 10/5, 5/10, 10/10, and 15/15) %. The experimental data were optimized using the extended Debye–Huckel, the Pitzer, and the modified Pitzer equations. The results of the apparent standard electromotive force E0* of the three equations are in good agreement. The mean activity coefficients and the standard Gibbs energy of transfer of RbCl or CsCl from pure water to mixed solvents (MeOH + EtOH + water) were also calculated.