Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

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 assist with X-ray diffraction method was 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 2 two-salt cosaturation invariant points, 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 co-saturated points, the equilibrium solid phases of the saturation points F1 and F2 are corresponding to [(Rb, Cs)2SO4] + Cs2SO4 and Rb2SO4 + [(Rb, Cs)2SO4], respectively, three monovariant curves, and three crystallization fields, is also a complex type at 298.2 K. Furthermore, under the investigated temperature, the Pitzer model was applied to calculate the solubilitites of these two ternary systems. Compared the predicted solubilities with the experimental solubilities, the results both indicated good consistency.