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

ABSTRACT

Solubilities, densities, refractive indices, and pH values in the ternary system (MgSO4 + Mg2B6O11 + H2O) at (288.15, 298.15 and 308.15) K and 0.1 MPa were determined with the isothermal dissolution equilibrium method for the first time. Based on the experimental data, the phase diagrams and the physicochemical property diagrams (density, refractive index and pH value) versus composition of magnesium sulfate were plotted. It was found that there are all one invariant point, two univariant curves and two crystallization regions corresponding to inderite (Mg2B6O11*15H2O, Inde) and epsomite (MgSO4*7H2O, Eps). The area of the crystallization region of inderite is larger than that of epsomite at three temperatures, and this result demonstrates that the solubility of inderite is lower than that of epsomite. A comparison of the phase diagrams at (288.15, 298.15 and 308.15) K shows that the area of Inde and Eps are all increased with the increasing of temperature. Neither solid solution nor double salts were formed in the ternary system at three temperatures. The density and refractive index in the ternary system at three temperatures change regularly with the increasing of magnesium sulfate content in solution. The densities and refractive indices were further correlated with the empirical equations, and the calculated values at the three temperatures agree well with the experimental results.