Metastable Phase Equilibrium in the Aqueous Ternary System K2SO4+MgSO4+H2O at (288.15 and 308.15) K

Abstract

The metastable solubilities and densities of the aqueous ternary system K2SO4+MgSO4+H2O at (288.15 and 308.15) K were determined with the isothermal evaporation method. Using the experimental results, the metastable phase diagram and the densities versus composition diagram were plotted. In the metastable phase diagrams of the ternary system at (288.15 and 308.15) K, there are in all two invariant points, three univariant solubility curves, and three metastable crystallization regions corresponding to arcanite (i.e., anhydrous potassium sulfate, K2SO4), picromerite (K2SO4⋅MgSO4⋅6H2O) and epsomite (MgSO4⋅7H2O) that are formed in the metastable equilibrium system. A comparison of the stable and metastable phase diagrams at each temperature shows that the metastable regions of magnesium sulfate are obvious, and the crystallizing regions of epsomite and arcanite are much larger than those in the stable phase diagram. The densities of the system changed regularly with the magnesium sulfate content. The resulting information can be used to recover potassium or remove magnesium. The calculated densities using an empirical equation agree well with the experimental results.