The solid-liquid equilibria in the quinary system Na^＋, K^＋//CI^-, SO4^2-, B4O7^2- -H2O at 298 K had been studied experimentally using the method of isothermal solution saturation. Solubilities and densities of the solution of the quinary system were measured experimentally. Based on the experimental data, the dry-salt phase diagram and water content diagram of the quinary system were constructed, respectively. In the equilibrium diagram of the quinary system Na^＋, K^＋//CI^-, SO4^2-, B4O7^2- -H2O at 298 K, there are five invariant points F1, F2, F3, F4 and F5; eleven univariant curves ELF1, E2F2, E3F3, E4F5, E5F2, E6F4, E7F5, F1F4, F2F4 F1F3 and F3F5, and seven fields of crystallization saturated with Na2B407 corresponding to Na2SO4, Na2SO4·10H2O, NazSO4-3K2SO4 （Gla）, K2SO4, K2B4O7·4H2O, NaC1 and KC1. The experimental results show that Na2SO4＂3KzSO4 （Gla）, K2SO4 and K2B4O7·4H2O have bigger crystallization fields than other salts in the quinary system Na^＋, K^＋//CI^-, SO4^2-, B4O7^2- -H2O at 298 K.
1 Introduction The underground brine resources distributing widely in Sichuan Basin,China have drawn worldwide attention due to their unusual element abundance and excellent quality.
