Solubilities of Salts in Quaternary System KBr-K2SO4-K2B4O7-H2O and Quinary System KCl-KBr-K2SO4-K2B4O7-H2O at 373 K

The underground brines are large reserves of valuable mineral resources. Aiming at the underground brines of western Sichuan Basin, the phase equilibria of quinary system KCl-KBr-K2SO4-K2B4O7-H2O and its quaternary subsystem KBr-K2SO4-K2B4O7-H2O were studied by using the method of isothermal dissolution equilibrium at 373 K. The phase diagrams, water content diagrams and density-composition relationship diagrams of above two systems were plotted by using the experimental data, respectively. The results show that the quaternary system KBr-K2SO4-K2B4O7-H2O belongs to a simple type; it consists of three univariant curves, one invariant point and three crystallization regions (K(2)B(4)O(7)4H(2)O, K2SO4, and KBr). The equilibrium phase diagram (saturated with K2SO4) in the quinary system KCl-KBr-K2SO4-K2B4O7-H2O is a type of solid solution, and there are two crystallization regions (K(2)B(4)O(7)4H(2)O, solid solution K(Cl,Br)) (saturated with K2SO4), one univariant curve and no invariant point.