No abstract

The (solid + liquid) phase equilibria of the NaBr + KBr + SrBr2 + H2O quaternary system and two subsystems (NaBr + SrBr2 + H2O and KBr + SrBr2 + H2O) were studied at T = 323 K using the isothermal dissolution method. With the solubility values of each system, the stable phase diagrams of these systems were drawn. It shows that there is neither solid solution nor double salt in the diagrams. The three systems are all of the hydrate type I, and only one invariant point is found in the phase diagrams of the three systems.

The mean activity coefficient of NaCl in NaCl− SrCl 2 −H 2 O was measured at 308 K by the electromotive force method. The total ion strength range of the mixed solution was 0.0100−1.0000 mol•kg −1 , and the ion intensity fraction of y b of SrCl 2 , i.e., y b = (0.8, 0.6, 0.4, 0.2, 0). A liquid-free electrochemical cell (Na-ISE | NaCl(m 1 ) SrCl 2 (m 2 )| Cl-ISE) was used to determine the electromotive force of a NaCl single salt and mixed solution. According to experimental data, the activity coefficient diagrams were drawn. The experimental results show that the measured activity coefficients are accurate and reliable, and the average activity coefficient of NaCl decreases with the increase of the ion strength of SrCl 2 . Using the measured average activity coefficient of NaCl, the parameters of the mixed ion action of the Pitzer equation θ Na + •Sr 2+ and φ Na + •Cl − •Sr 2+ are fitted. Furthermore, the Pitzer equation is used to calculate the average activity coefficents of SrCl 2 , the water activities a w , osmotic coefficients Φ, and Gibbs free energies G E of the mixed system.