Measurements and Calculations of Stable Phase Equilibria in Ternary Systems MgSO4(Rb2SO4) + Cs2SO4 + H2O at T = 298.2 K

Abstract

The components (solubilities and densities) in aqueous stable equilibria systems Cs2SO4 + MgSO4 + H2O and Rb2SO4 + Cs2SO4 + H2O at T = 298.2 K have been studied by the isothermal dissolution equilibrium method. The wet residue method and the X-ray diffraction method were used to confirm the solid phase compositions. The ternary system Cs2SO4 + MgSO4 + H2O is a complex saturated type, with the commensurate double salt Cs2SO4·MgSO4·6H2O formed at the investigated temperature. There are two two-salt cosaturation invariant points, with the coexisting solid phases corresponding to commensurate type saturation points E1 (MgSO4·7H2O + Cs2SO4·MgSO4·6H2O) and E2 (Cs2SO4·MgSO4·6H2O + Cs2SO4), three monovariant curves, and three crystallization fields in the system of Cs2SO4 + MgSO4 + H2O. The ternary system Rb2SO4 + Cs2SO4 + H2O with solid solutions formed contains two cosaturated points, with the equilibrium solid phases of the saturation points F1 and F2 corresponding to [(Rb, Cs)2SO4] + Cs2SO4 and Rb2SO4 + [(Rb,...