(Solid + liquid) equilibria in the quinary system Na+,Mg2+,K+SO42−,B4O72−-H2O at 288 K

The solubilities and densities of the solid-liquid equilibrium in the quinary system Na+, Mg2+, K+SO42−, B4O72−-H2O 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 Mg2+ content diagram of the quinary system were constructed. In the equilibrium phase diagram of the quinary Na+,Mg2+, K+SO42−, B4O72−−H2O system at 288 K, there are seven invariant points, fourteen univariant curves, and eight fields of crystallization (saturated with MgB4O7⋅9H2O) corresponding to Na2B4O7⋅10H2O, K2B4O7⋅4H2O, K2SO4, Na2SO4⋅10H2O, MgSO4⋅7H2O, K2SO4⋅MgSO4⋅6H2O, Na2SO4⋅MgSO4⋅4H2O, and Na2SO4⋅3K2SO4. The experimental results show that sulfates have larger solubilities than borates in the quinary Na+, Mg2+, K+SO42−, B4O72−-H2O system at 288 K.