Studies On The Metastable Phase Equilibrium In Quinary System Li⁺, Na⁺, (K⁺)//CO₃^2-, B₄O₇^2-, (Cl^-)-H₂O At 273K

In this paper, the phase equilibria of two quinary systems Li⁺, Na⁺, K⁺//CO₃^2-, B₄O₇^2--H₂O and Li⁺, Na⁺//Cl-, CO₃^2-, B₄O₇^2--H₂O at 273 K were studied using an isothermal evaporation method. Its subsystems, one ternary system Na₂CO₃-Na₂B₄O₇-H₂O and two quaternary systems Li⁺, Na⁺//Cl-, CO₃^2--H₂O and Li⁺, Na⁺//Cl-, B₄O₇^2--H₂O were also studied at 273 K. The salts'solubility and the density of the solution in these systems were determined. According to the experimental data, the equilibrium phase diagram and density-composition diagram of the ternary system were plotted. The equilibrium phase diagrams and water content diagrams of quaternary systems were finished. The stereo phase diagram, the projected phase diagram (saturated with Li₂CO₃), density-composition diagrams, water content diagrams, and sodium content diagram of the quinary systems were also plotted.The ternary system Na₂CO₃-Na₂B₄O₇-H₂O at 273 K is of simple eutectic type, no double salt or solid solution was found. Salt sodium carbonate has salting-in effect on salt sodium borate.The two quaternary systems Li⁺, Na⁺//Cl-, CO₃^2--H₂O and Li⁺, Na⁺ // Cl-, B₄O₇^2- - H₂O at 273 K are all of simple eutectic type and no double salt or solid solution is formed. LiCl was strongly salting-out effect Li₂CO₃, Li₂B₄O₇ and NaCl. Na₂B₄O₇ has salting-in effect on Li₂B₄O₇.The phase diagram of the quinary system Li⁺, Na⁺, K⁺//CO₃^2-, B₄O₇^2--H₂O at 273 K consists of seven crystallization fields, nine univariant curves and four invariant points. The seven crystallization fields correspond to Li₂CO₃ , K₂CO₃·3/2H₂O, Na₂CO₃·10H₂O, LiBO₂·8H₂O, Na₂B₄O₇·10H₂O,K₂B₄O₇·4H₂O and K₂CO₃·Na₂CO₃·12H₂O. The coexisted salts of the invariant points are Li₂CO₃+ LiBO₂·8H₂O+ K₂B₄O₇·4H₂O+ Na₂B₄O₇·10H₂O, Li₂CO₃+ Na₂CO₃·10H₂O+ K₂B₄O₇·4H₂O+ Na₂B₄O₇·10H₂O, Li₂CO₃+ Na₂CO₃·10H₂O+ K₂CO₃·3/2H₂O+ K₂CO₃·Na₂CO₃·12H₂O and Li₂CO₃+ Na₂CO₃·10H₂O+ K₂CO₃·3/2H₂O+ K₂CO₃·Na₂CO₃·12H₂O, respectively. There is obviously salting-in effect among borate in the system. Potassium carbonate (K₂CO₃) has strong salting-out effect on borate salt in the system.The phase diagram of the quinary system Li⁺, Na⁺//Cl-, CO₃^2-, B₄O₇^2--H₂O at 273 K consists of six crystallization fields, six univariant curves and four invariant points. The six crystallization fields correspond to Na₂CO₃·10H₂O, LiBO₂·8H₂O, Na2B2O4·10H₂O, LiCl·H₂O, NaCl and Li₂CO₃. The coexisted salts of the invariant points are Li₂CO₃+ Na₂CO₃·10H₂O+ NaCl+ Na₂B₄O₇·10H₂O, Li₂CO₃+ LiBO₂·8H₂O+ NaCl+ LiCl·H₂O, Li₂CO₃+ NaCl+ LiCl·H₂O+ Na₂B₄O₇·10H₂O. LiCl was strongly salting-out effect NaCl and Na₂CO₃.