Solid–Liquid Phase Equilibria in the Aqueous Systems (CaCl2 + SrCl2 + H2O) and (NaCl + CaCl2 + SrCl2 + H2O) at 288.15 K

The solubilities of the ternary system (CaCl2 + SrCl2 + H2O) and the quaternary system (NaCl + CaCl2 + SrCl2 + H2O) at T = 288.15 K and P = 0.1 MPa were investigated experimentally with the method of isothermal dissolution equilibrium, and the corresponding phase diagrams were plotted. Compared with the phase diagram of the ternary system (CaCl2 + SrCl2 + H2O) at 291.15 K, which only includes one crystallization region of a completely miscible solid solution (Ca,Sr)Cl2·6H2O, there were also the pure single salts CaCl2·6H2O and SrCl2·6H2O found in the ternary system at 288.15 K besides the crystallization of the solid solution (Ca,Sr)Cl2·6H2O. The solid solution of (Ca,Sr)Cl2·6H2O was also formed in the quaternary system (NaCl + CaCl2 + SrCl2 + H2O) at 288.15 K, and there were four crystalline fields in the quaternary system, which correspond to the single salts NaCl, SrCl2·6H2O, CaCl2·6H2O, and the solid solution (Ca,Sr)Cl2·6H2O, respectively. On the basis of the analyses of the phase diagrams of (CaCl2 + SrCl2 + H2O) and (NaCl + CaCl2 + SrCl2 + H2O) at 288.15 K, CaCl2·6H2O and SrCl2·6H2O can be separated from each other through avoiding crystallization in the solid solution crystallization region in the systems, and SrCl2·6H2O and NaCl can be produced using CaCl2 as the salting-out agent directly.