Studies On Equilibria In Quinary System Na⁺, K⁺∥Cl^-, SO₄^2-, B₄O₇^2--H₂O At373K

Phase equilibria of reciprocal quinary system Na⁺, K⁺∥Cl^-，SO₄^2-, B₄O₇^2--H₂O at373K and phase equilibria of quaternary system Na⁺//Cl^-, Br^-, SO₄^2--H₂O at348Kwere determinded by isothermal solution quilibrium. Subsystems of the reciprocalquinary system which included two ternary systems, K⁺//SO₄^2-, B₄O₇^2--H₂O, Na+, K+//SO₄^2--H₂O and three quaternary systems, K⁺∥Cl^-，SO₄^2-, B₄O₇^2--H₂O, Na⁺, K⁺//Cl^-, SO₄^2--H₂O and Na⁺, K⁺//SO₄^2-, B₄O₇^2--H₂O, were studied by isothermal solutionequilibrium method. The solubilities and densities of system listed above at373Kwere mensurated, also the solubilities and densities of quaternary system listed at348K were mensurated. According to the experimental data, the equilibria phase diagramsand density-composition diagrams of the relevant system were plotted. Equilibriumphase diagrams and corresponding water content diagrams of quaternary systemswere finished. The phase diagram, corresponding water content diagram andcorresponding Na+content diagram of the quinary system at373K （saturated withNa₂B₄O₇） were also plotted.The experimental results show that the ternary system K⁺//SO₄^2-, B₄O₇^2--H₂O at373K is of simple eutectic type and no double salt or solid solution is found. Inthe phase diagram, the ternary system has one invariant point, two univariant curves,two fields of crystallization [K₂B₄O₇4H₂O and K₂SO₄].The experimental results show that the ternary system Na⁺, K⁺//B₄O₇^2--H₂O at373K is of simple eutectic type and no double salt or solid solution is found. In thephase diagram, the ternary system has one invariant point, two univariant curves, twofields of crystallization [K₂B₄O₇4H₂O and Na₂B₄O₇5H₂O].The quaternary system K⁺∥Cl^-，SO₄^2-, B₄O₇^2--H₂O at373K is of simple eutectictype and no double salt or solid solution is found. In the phase diagram, the quaternarysystem has one invariant point, three univariant curves, three fields of crystallization[KCl, K₂B₄O₇4H₂O and K₂SO₄].There is no double salt in the quaternary system Na⁺, K⁺∥Cl^-，SO₄^2-, B₄O₇^2-at 373K. In the phase diagram, this quaternary system has two invariant points, fiveunivariant curves, four fields of crystallization [Na₂B₄O₇5H₂O, K₂B₄O₇4H₂O, NaCland KCl].The double salt Na₂SO₄3K₂SO₄forms in the quaternary system Na⁺, K⁺//B₄O₇^2--H₂O at373K. In the phase diagram, this quaternary system has three invariantpoints, seven univariant curves, five fields of crystallization [Na₂B₄O₇5H₂O, Na₂SO₄,K₂SO₄, K₂B₄O₇4H₂O and Na₂SO₄3K₂SO₄].In stable equilibrium phase diagram of quinary system Na+, K+//Cl-, SO42-,B₄O₇^2--H₂O at373K, the double salt Na₂SO₄3K₂SO₄forms, there are four invariantpoints, nine uninvariant curves, and six crystallization fields （saturated with Na₂B₄O₇）:[Na₂SO₄, Na₂B₄O₇5H₂O, K₂SO₄, Na₂SO₄3K₂SO₄, K₂B₄O₇4H₂O and KCl].The quaternary system Na⁺//Cl^-, Br^-, SO₄^2--H₂O at348K is of simple eutectictype and contained solid solution. In the phase diagram, The quaternary system hasone invariant point and two crystallization fields: Na（Cl, Br） and Na₂SO₄. Theexperimental results show that the sodium bromide has the salting-out effect onsodium chloride.