The solid–liquid phase equilibria of the ternary system KBr–LiBr–H2O at 273 and 308 K were determined by the isothermal dissolution equilibrium method. On the basis of the obtained experimental data, the stable phase diagrams of ternary system KBr–LiBr–H2O at 273 and 308 K were plotted, respectively. The results show that the ternary system is a simple cosaturated type at two different temperatures, and there is neither a solid solution nor a double salt in the system. Both of the phase diagrams include one invariant point, two univariant curves, and two crystalline regions (where the solids are LiBr·2H2O and KBr, respectively). The crystalline area of KBr is much larger than that of LiBr·2H2O, indicating that the solubility of KBr is much smaller than that of LiBr in the ternary system. The mass fraction of KBr in the equilibrium liquid phase is obviously reduced, which indicates that LiBr has a strong salting-out effect on KBr.

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In this work, the studies of thermodynamic mean activity coefficients of KCl in the KCl−SrCl 2 −H 2 O ternary system have been made. A cell without liquid junction battery cell, K−ISE|KCl(m A ), SrCl 2 (m B )|Cl−ISE, was used to study the activity coefficients in this mixed system KCl− SrCl 2 −H 2 O at 288.15 K by the electromotive force method. The total ionic strengths ranges are 0.0100−1.0000 mol•kg −1 with different ionic strength fractions y b of SrCl 2 , that is, y b = (0, 0.2, 0.4, 0.6, and 0.8). The results show that the K−ISE and Cl−ISE have a good Nernst response. Accordingly, the electromotive forces of the mixed system were measured by using the ion selective electrode listed above, and the mean activity coefficients are also determined with Nernst equation. Using the activity coefficient data, the mixed ion interaction parameters θ K,Sr and ψ K,Sr,Cl of Pitzer equations at 288.15 K were fitted by Matlab with linear regression method, respectively. Furthermore, those parameters were applied to calculate the values of the mean activity coefficients of SrCl 2 . Finally, the osmotic coefficients, water activity, and the excess Gibbs free energy of this system were evaluated by Pitzer's equations.

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In this article, research on the thermodynamic mean activity coefficients for the ternary system (NaCl–SrCl2–H2O) has been carried out. A cell without a liquid junction can be expressed as sodium–ISE|sodium chloride (m A), strontium chloride (m B)|chlorine–ISE. It is used to determine the activity coefficients in these mixtures at 278.15 K by the cell potential method. Then, the total ionic strengths are I = 0.0100–3.0000 mol·kg–1 with different y b (ionic strength fraction) = (0.0, 0.2, 0.4, 0.6, and 0.8). The relationship diagrams between γ±NaCl (mean activity coefficients of NaCl) and y b (ionic strength fraction) were plotted. Mixed interaction parameters θNa,Sr and ψNa,Sr,Cl of this system in Pitzer equations at 278.15 K were fitted by using the determined activity coefficients and multiple regression method. In addition, those obtained parameters were also used to calculate γ±SrCl2 (mean activity coefficients of SrCl2) by the Pitzer equations. Accordingly, the osmotic coefficients, water activity, and excess Gibbs free energy in the mixtures were studied in detail.