(Solid + liquid) phase equilibria in the quaternary systems LiCl–Li2SO4–MgCl2–MgSO4–H2O and KCl–K2SO4–MgCl2–MgSO4–H2O at 288.15 K

The experimental solubility of LiCl–Li 2 SO 4 –MgCl 2 –MgSO 4 –H 2 O and KCl–K 2 SO 4 –MgCl 2 –MgSO 4 –H 2 O systems was measured at 288.15 K. The corresponding stable phase diagrams and water content diagrams were plotted by experimental results. Double salt was formed in both two systems. There are six phase fields, nine univariant solution curves and four invariant points in the phase diagram of LiCl–Li 2 SO 4 –MgCl 2 –MgSO 4 –H 2 O system. And the diagram of another system has seven invariant points and eight crystallization regions. By using multiple linear regression method, parameter Ψ Li,Cl,SO4 and the solubility equilibrium constants of double salt KCl·MgSO 4 ·3H 2 O were obtained by solubility data fitting at 288.15 K. The equilibrium solubility of salts in above systems at the same temperature was predicted with Pitzer's electrolyte solution model and mathematical calculation software. The results indicate that the predicted data are in correspondence with experiments.