Study On Equilibria In Quinary System Li⁺, K⁺, Mg²⁺//SO₄^2-, B₄O₇^2--H₂O At 288K

Phase equilibria of reciprocal quinary system Li+, K+, Mg2+ //SO42-, B4O72--H2O and three quaternary systems (two simple quaternary systems Li+, K+, Mg2+//B4O72--H2O and Li+, Na+, K+//SO42--H2O; one reciprocal quaternary system Li+, K+//SO42-, B4O72--H2O) at 288K were studied by isothermal solution equilibrium method. Solubilities and densities in the solution of above listed were determined experimentally. According to the experimental data, the equilibrium phase diagrams and density-composition diagrams of the quaternary systems were plotted. The phase diagram, corresponding water content diagram and corresponding Mg2+ content diagram of the quinary system at 288K ( saturated with MgB4O7·9H2O ) were also plotted.The simple quaternary system Li+, K+, Mg2+//B4O72--H2O was simple eutectic type and no double salt or solid solution was found. In the phase diagram, the quaternary system has one invariant point, three univariant curves, and three fields of crystallization Li2B4O7·3H2O, K2B4O7·4H2O and MgB4O7·9H2O. The experimental results show that K2B4O7·4H2O had strong salting-out effect on Li2B4O7·3H2O .The double salt KLiSO4 was found in the reciprocal quaternary system Li+, K+//SO42-, B4O72--H2O at 288K. The quaternary system has three invariant points, seven univariant curves, five fields of crystallization Li2B4O7·3H2O, Li2SO4·H2O, K2B4O7·4H2O, K2SO4 and KLiSO4. The experimental results show that Li2SO4·H2O had strong salting-out effect on other salts.The double salt K3Na(SO4)2, Na3Li(SO4)2·6H2O, KLiSO4 and the triple salt Li2NaK(SO4)2 were found in the reciprocal quaternary system Li+, K+,Na+//SO42--H2O at 288K. The quaternary system has six invariant points, twelve univariant curves, seven fields of crystallization K2SO4, KLiSO4, K3Na(SO4)2, Na3Li(SO4)2·6H2O, Na2SO4·10H2O, Li2SO4·H2O and Li2NaK(SO4)2.The double salt K2SO4·MgSO4·6H2O and KLiSO4 were found in the reciprocal quinary system Li+, K+, Mg2+ //SO42-, B4O72--H2O at 288K. The quinary system has six invariant points, nine univariant curves, seven fields of crystallization K2B4O7·4H2O, Li2SO4·H2O, Li2B4O7·3H2O, K2SO4, MgSO4·7H2O, K2SO4·MgSO4·6H2O and KLiSO4. The salt Li2SO4·H2O had the biggest solubilities and strong salting-out effect on other salts.