Mean Activity Coefficients of NaCl in the Ternary System NaCl–SrCl₂–H₂O at 288.15 K Determined by the Cell Potential Method and Their Application to the Prediction of Phase Equilibria

Mean activity coefficients for NaCl in the mixed salt solution NaCl–SrCl2–H2O at 288.15 K were determined from cell potential measurements of the cell: Na-ISE |NaCl (m1), SrCl2 (m2)| Cl-ISE at total ionic strengths ranging from 0.0100 to 4.0000 mol kg–1. Different ion strength fractions (yb) of SrCl2 were used. The ionic interaction parameters of the Pitzer model were fitted. In addition, the mean activity coefficients of NaCl and SrCl2, along with the Gibbs free energy, the osmotic coefficient, and the water activity of the solution, were calculated. Furthermore, the solubilities of salts in the NaCl–SrCl2–H2O system at 288 K were predicted, and the results are in agreement with the experimental values from the literatures. Through linear regression, this work obtained the parameters (θNa+·Sr2+=0.11147, ψNa+·Cl−·Sr2+=−0.02470) at 288.15 K and other parameters at temperatures reported in the literature, and the relationship equations for the parameters of the mixed ions of the Pitzer model at temperatures ranging from 273 to 328 K have been established. The solubilities at various temperatures are calculated and compared with experimental values from the literatures. The predicted results show that the ion interaction parameter equation of the Pitzer model at 273 ∼ 328 K is reliable.