Stable Phase Equilibria in the Quinary System Li+,Na+,Mg2+//Cl–,B4 $${\text{O}}_{7}^{{2 - }}$$ –H2O at 273 K

The isothermal dissolution method was used to study the stable phase equilibria in the quinary system Li+,Na+,Mg2+//Cl–,B4 $${\text{O}}_{7}^{{2 - }}$$ –H2O at 273 K. The dry salt diagram, sodium diagram and water diagram in the quinary system were plotted respectively when Sodium chloride (NaCl) is saturated. The experimental results show that a complex salt lithium carnallite (LiCl·MgCl2·7H2O) is formed in the system. The dry base diagram of this system saturated with NaCl consists of four invariant points, nine univariate curves, and six crystalline regions. The crystalline regions are lithium borate trihydrate (Li2B4O7·3H2O), sodium borate decahydrate (Na2B4O7·10H2O), magnesium borate nonahydrate (MgB4O7·9H2O), lithium chloride dihydrate (LiCl·2H2O), magnesium chloride hexahydrate (MgCl2·6H2O), and the double salts lithium carnallite (LiCl·MgCl2·7H2O), among which sodium borate decahydrate (Na2B4O7·10H2O) has the largest crystalline area that shows that Na2B4O7·10H2O is the easiest to precipitate.