Study On Equilibria In Quinary System Na⁺, K⁺//Cl^-, SO₄^2-, B₄O₇^2--H₂O At 323 K And 298 K

Phase equilibria of reciprocal quinary system Na+, K+// Cl-, SO42-, B4O72--H2O at 298 K and 323 K and its subsystems which included two simple eutectic type systems: K2B4O7 - K2SO4 - KCl - H2O and Na2B4O7 - Na2SO4 - NaCl - H2O, Na+, K+ //SO42-, B4O72--H2O at 298 K, 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 298 K ( saturated with NaCl) were also plotted.The experimental results show that the quaternary system Na2B4O7 - Na2SO4 - NaCl - 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 NaCl]. The experimental results show NaCl had the salting-out effect on Na2B4O7·4H2O and Na2SO4 .The quaternary system K2B4O7 - K2SO4 - KCl - 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 [KCl, K2B4O7·4H2O and K2SO4]. The experimental results show that KCl had the salting-out effect on K2B4O7·4H2O and K2SO4 .There is no double salt in the quaternary system Na+, K+// Cl-, 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, NaCl and KCl].In stable equilibrium phase diagram of quinary system Na+, K+// Cl-,SO42-, B4O72--H2O at 323 K, there are the double salt Na2SO4·3K2SO4, nine uninvariant curves, four invariant points, six crystallization fields (saturated with Na2B4O7): [Na2SO4, NaCl, K2SO4, Na2SO4·3K2SO4(Gla), K2B4O7·4H2O and KCl].In stable equilibrium phase diagram of quinary system Na+, K+ //Cl-, SO42-, B4O72--H2O at 298 K, there are the double salt Na2SO4·3K2SO4 ,eleven uninvariant curves, five invariant points, and seven crystallization fields (saturated with Na2B4O7): [Na2SO4, Na2SO4·10H2O, Na2SO4·3K2SO4(Gla), K2SO4,K2B4O7·4H2O, NaCl and KCl].