Solid–Liquid Equilibria in the Quinary system Na+, K+//Cl–, Br–, SO42––H2O at 373 K

Solid–liquid equilibria in the quinary system Na+, K+//Cl–, Br–, SO42––H2O at 373 K were measured by the isothermal solution saturation method, and the equilibrium solid phases, solubilities and densities of saturated solutions were determined experimentally. Using the experimental results, the dry salt phase diagrams, water diagrams, and the densities versus composition diagrams were plotted (saturated with Na2SO4 and K2SO4, respectively). The experimental results show that there is solid solution formed in the quinary system Na+, K+//Cl–, Br–, SO42––H2O at 373 K. The two projected phase diagrams of this system all consist of one univariant curve, two crystallization fields, and have no invariant point. Saturated with the salt Na2SO4, the crystallization forms are the double salt Na2SO4·3K2SO4 (Gla) and the solid solution Na(Cl,Br); the two crystallization forms are Na2SO4·3K2SO4 (Gla) and the solid solution K(Cl,Br) saturated with the salt K2SO4.