Solubility prediction for the HCl–MgCl2–H2O system at 40 ∘C and solubility equilibrium constant calculation for HCl ⋅ MgCl2 ⋅ 7H2O at 40 ∘C

The component solubilities of the HCl–MgCl2–H2O system at 40 ∘C were calculated by using Pitzer’s ion-interaction model and the solubility equilibrium constant of HCl⋅MgCl2⋅7H2O at 40 ∘C was evaluated according to the solubility data for the HCl–MgCl2–H2O system at −19.8, 0, 20, 25 and 50 ∘C. This study can provide the parameters necessary for solubility prediction for the HCl–LiCl–MgCl2–H2O system at 40 ∘C and supply a theoretical basis for the manufacturing process which was proposed by Gao and employed to extract MgCl2⋅6H2O from salt lake brine.