SOLID-LIQUID STABLE PHASE EQUILIBRIA OF THE TERNARY SYSTEMS MgCl2 + MgB6O_(10)+ H2O AND MgSO4 + MgB6O_(10) + H2O AT 308.15 K

摘要

The solubilities and the relevant physicochemical properties of the ternary systems MgCl2 + MgB6O_(10) + H2O and MgSO4 + MgB6O_(10) + H2O at 308.15 K were investigated using an isothermal dissolution method. It was found that there is one invariant point, two univariant curves, and two crystallization regions of the systems. The systems belong to a simple co-saturated type, and neither double salts nor solid solutions were found. Based on the extended HW model and its temperature-dependent equations, the single-salt Pitzer parameters β~(o), β~(1), β~(2) and C for MgCl2, MgSO4, and Mg(B6O7)(OH)6, the mixed ion-interaction parameters θ_(CL,B6O_(10) θ_(SO4,B6O_(10)Ψ_(Mg,Cl,B6O_(10) Ψ_(Mg,SO4,B6O_(10)of the systems at 308.15 K were fitted ,In addition, the average equilibrium constants of the stable equilibrium solids at 308.15 K were obtained by a method using the activity product constant. Then the solubilities of the ternary systems are calculated. The calculated solubilities agree well with the experimental values.