Thermodynamic investigation of RbF + Rb2SO4 + H2O and CsF + Cs2SO4 + H2O ternary systems by potentiometric method at 298.2 K

In this paper, the potentiometric method was carried out to investigate the thermodynamic properties of the RbF + Rb2SO4 + H2O and CsF + Cs2SO4 + H2O ternary systems over total ionic strengths from (0.01–0.70) mol·kg−1 for different ionic strength fractions yB of Rb2SO4/Cs2SO4 with yB = 0.00, 0.30, 0.60 and 0.90, at 298.2 K. The Harned model and the Pitzer model were used to correlate the experimental data. The Harned coefficients and the Pitzer mixing parameters were evaluated by multiple linear regression technique. Moreover, the mean ionic activity coefficients of RbF/CsF and Rb2SO4/Cs2SO4, the osmotic coefficients, and the excess Gibbs energies of the studied systems were calculated, respectively. Thermodynamic properties, such as mean activity coefficients, osmotic coefficients and excess Gibbs free energies, of the RbF + Rb2SO4 + H2O and CsF + Cs2SO4 + H2O ternary systems were investigated by potentiometric method at 298.2 K. The Harned rule and the Pitzer model were used to correlate the experimental data. [Display omitted] •Thermodynamic properties of RbF + Rb2SO4 + H2O and CsF + Cs2SO4 + H2O ternary systems were studied.•The exprimental data were fitted using Harned rule Pitzer model.•The activity coefficients, the osmotic coefficients, and the excess Gibbs free energy were calculated.