Study On Equilibria In Quinary System Na⁺, K⁺//Br^-, SO₄^2-, B₄O₇^2--H₂O At 323K

Phase equilibria of reciprocal quinary system Na+,K+//Br-, SO42-,B4O72--H2O at 323 K and its subsystems which included two ternary systems and four quaternary systems:K2B4O7-K2SO4-KBr-H2O, Na2B4O7-Na2SO4-NaBr-H2O, Na+, K+//Br-, B4O72--H2O and Na+, K+//Br-, SO42--H2O, were studied by isothermal solution equilibrium method. The solubilities and densities of listed above at a specifically temperature were mensurated. According to the experimental data, the equilibria phase diagrams and density-composition diagrams of the relevant system were plotted. Equilibrium phase diagrams and corresponding water content diagrams of quaternary systems were finished. The phase diagram, corresponding water content diagram and corresponding Na+content diagram of the quinary system at 323 K (saturated with Na2B4O7) were also plotted.The experimental results show that the ternary system Na2SO4-NaBr-H2O at 323 K was of simple eutectic type and no double salt or solid solution was found. In the phase diagram, the ternary system has one invariant point, two univariant curves, two fields of crystallization [Na2SO4 and NaBr·2H2O]. The experimental results show NaBr had the salting-out effect on Na2SO4.The experimental results show that the ternary system Na2B4O7-NaBr-H2O at 323 K was of simple eutectic type and no double salt or solid solution was found. In the phase diagram, the ternary system has one invariant point, two univariant curves, two fields of crystallization [Na2B4O7·10H2Oand NaBr·2H2O]. The experimental results show NaBr had the salting-out effect on Na2B4O7·10H2O.The quaternary system Na2B4O7-Na2SO4-NaBr-H2O at 323 K 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, three fields of crystallization [Na2B4O7·10H2O, Na2SO4 and NaBr·2H2O]. The experimental results show that NaBr had the salting-out effect on Na2B4O7·10H2O and Na2SO4.The quaternary system K2B4O7-K2SO4-KBr-H2O at 323 K 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, three fields of crystallization [KBr, K2B4O7·4H2O and K2SO4]. The experimental results show that KBr had the salting-out effect on K2B4O7-4H2O and K2SO4.There is no double salt in the quaternary system Na+, K+//Br-, B4O72--H2O at 323 K. In the phase diagram, this quaternary system has two invariant points, five univariant curves, four fields of crystallization [Na2B4O7·10H2O, K2B4O7·4H2O, NaBr·2H2O, and KBr].The double salt Na2SO4·3K2SO4 forms in the quaternary system Na+, K+//Br-, SO42--H2O at 323 K. In the phase diagram, this quaternary system has three invariant points, seven univariant curves, five fields of crystallization [NaBr·2H2O, Na2SO4, K2SO4, KBr and Na2SO4·3K2SO4].In stable equilibrium phase diagram of quinary system Na+, K+//Br-, SO42-, B4O72--H2O at 323 K, there are the double salt Na2SO4-3K2SO4, four invariant points, nine uninvariant curves, and six crystallization fields (saturated with Na2B4O7): [Na2SO4, NaBr·2H2O, K2SO4, Na2SO4·3K2SO4 (Gla), K2B4O7-4H2O and KBr].