Solid–Liquid Phase Equilibria in the Ternary Systems NaCl–ZnCl2–H2O and CaCl2–ZnCl2–H2O at 323 K

This paper describes the results of the solid–liquid equilibria phase diagram in the two ternary systems sodium chloride–zinc chloride–water and calcium chloride–zinc chloride–water at 323 K using the method of isothermal dissolution equilibrium. Integrated with the determined equilibrated liquid phase and humid residue composition, the phase diagrams of the two systems were generated. At the same time, the invariant points, the univariant solubility curves, and the solid crystalline phase regions are displayed and discussed. The results of the experiment testify that the types of two ternary systems are classified as complex owing to the formation of a double salt. The phase diagram of the ternary system NaCl–ZnCl2–H2O at 323 K is constituted of two eutectic points, three univariant solubility curves, and three solid crystalline phase regions corresponding to NaCl, ZnCl2, and 2NaCl·ZnCl2. The phase diagram of the ternary system CaCl2–ZnCl2–H2O at 323 K includes two eutectic points, three univariant solubility curves, and three solid crystalline phase regions corresponding to CaCl2·2H2O, CaCl2·ZnCl2·2H2O, and ZnCl2. The experimental densities of the equilibrium solution were measured using a density bottle method. Based on the Laliberte model, the theoretical density of each saturated solution was calculated. The results show that the model gives worse prediction for two ternary systems with stronger interactions between components.