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

Phase equilibria of the reciprocal quinary system Li⁺,Mg²⁺//Cl^-,SO₄^2-,B₄O₇^2-- H₂O and its subsystems (Including two simple quaternary systems Mg²⁺//Cl^-,SO₄^2-,B₄O₇^2--H₂O and Li⁺//Cl^-,SO₄^2-,B₄O₇^2--H₂O , two reciprocal quaternary systems Li⁺,Mg²⁺//SO₄^2-, B₄O₇^2- -H₂O and Li⁺,Mg²⁺//Cl^-, B₄O₇^2--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 quaternary system Mg²⁺//Cl^-,SO₄^2-,B₄O₇^2--H₂O was of 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 MgB₄O₇·9H₂O,MgCl₂·6H₂O and MgSO₄·7H₂O.The quaternary system Li⁺//Cl^-, SO₄^2-,B₄O₇^2--H₂O was of 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 LiCl·H₂O,Li₂SO₄·H₂O and Li₂B₄O₇·3H₂O. The experimental results show that LiCl·H₂O had very strong salting-out effect on Li₂B₄O₇·3H₂O and Li₂SO₄·H₂O.The quaternary system Li⁺, Mg²⁺//SO₄^2-, B₄O₇^2- -H₂O was of simple eutectic type and no double salt or solid solution was found. In the phase diagram, the quaternary system has two invariant points, five univariant curves, and four fields of crystallization Li₂SO₄·H₂O,Li₂B₄O₇·3H₂O,MgSO₄·7H₂O and MgB₄O₇·9H₂O. The experimental results show that the double salt LiCl·MgCl₂·7H₂O forms in the quaternary system Li⁺,Mg²⁺//Cl^-,B₄O₇^2--H₂O at 288K. The quaternary system has three invariant points, seven univariant curves, and five fields of crystallization LiCl·H₂O,Li₂B₄O₇·3H₂O,LiCl·MgCl₂·7H₂O,MgCl₂·6H₂O and MgB₄O₇·9H₂O. The experimental results show that the double salt LiCl·MgCl₂·7H₂O forms in the quaternary system Li⁺,Mg²⁺//Cl^-,B₄O₇^2--H₂O at 288K.In stable equilibrium phase diagram of the quinary system Li⁺,Mg²⁺,// Cl^-,SO₄^2-,B₄O₇^2--H₂O at 288K, there are the double salt LiCl·MgCl₂·7H₂O , four invariant points, nine univariant curves, and six crystallization fields (saturated with MgB₄O₇·9H₂O): LiCl·H₂O,Li₂SO₄·H₂O,Li₂B₄O₇·3H₂O,MgCl₂·6H₂O,MgSO₄·7H₂O and LiCl·MgCl₂·7H₂O.The salt LiCl·H₂O had the biggest solubilities and very strong salting-out effect on other salts, especially for Li₂SO₄·H₂O.