(Solid + liquid) equilibria in the quinary system [formula omitted] at 288 K

Abstract

The solubilities and densities of the solid–liquid equilibrium in the quinary system Na +, Mg 2+, K + SO 4 2 − , B 4O 7 2−–H 2O at 288 K were studied experimentally using the method of isothermal solution saturation. On the basis of the experimental data, the dry salt phase diagram, water content diagram and Mg 2+ content diagram of the quinary system were constructed. In the equilibrium phase diagram of the quinary Na +,Mg 2+, K + SO 4 2 − , B 4O 7 2−−H 2O system at 288 K, there are seven invariant points, fourteen univariant curves, and eight fields of crystallization (saturated with MgB 4O 7⋅9H 2O) corresponding to Na 2B 4O 7⋅10H 2O, K 2B 4O 7⋅4H 2O, K 2SO 4, Na 2SO 4⋅10H 2O, MgSO 4⋅7H 2O, K 2SO 4⋅MgSO 4⋅6H 2O, Na 2SO 4⋅MgSO 4⋅4H 2O, and Na 2SO 4⋅3K 2SO 4. The experimental results show that sulfates have larger solubilities than borates in the quinary Na +, Mg 2+, K + SO 4 2 − , B 4O 7 2−–H 2O system at 288 K.