Investigation of Solid–Liquid Equilibria on the System Na+, K+//Cl–, SO42––H2O and Na+, K+// SO42––H2O at 313.15 K

Abstract

Solid–liquid equilibria on the reciprocal quaternary system (Na+, K+//Cl–, SO42––H2O) and its ternary system (Na+, K+// SO42––H2O) at 313.15 K are studied with the method of isothermal solution saturation. The solubilities and physical properties (nD, η, ρ) of saturated solutions in the two systems are determined. The phase diagram of the ternary system at 313.15 K includes two invariant points, three invariant curves, and three fields of crystallization of single salts corresponding to K2SO4, Na2SO4·3K2SO4, Na2SO4. The two invariant points are cosaturated with two salts, that is (K2SO4 + Na2SO4·3K2SO4) and (Na2SO4 + Na2SO4·3K2SO4), respectively. The reciprocal quaternary system at 313.15 K is divided into seven univariant curves, three invariant points cosaturated with three-salts and five crystallization fields. A double salt Na2SO4·3K2SO4 can be proven to exist in the reciprocal quaternary system (Na+, K+//Cl–, SO42––H2O) and the ternary system (Na+, K+// SO42––H2O) under phase equilibrium conditions a...