Liquid-solid equilibria in the quinary system Na+, K+‖Br−, SO42−, B4O72−−H2O at 298 K

Abstract

Solid-liquid equilibria in the quinary system Na⁺, K⁺‖Br⁻, SO₄²⁻, B₄O₇²⁻−H₂O at 298 K were measured by isothermal solution saturation method. The solubilities of salts and the densities of saturated solutions in the system were determined. Using the experimental data, phase diagram, Na⁺ content diagram, water content diagram and density-composition diagram were constructed, respectively. The double salt Na₂SO₄ · 3K₂SO₄ (Gla) was found in the quinary system Na⁺, K⁺‖Br⁻, SO₄²⁻, B₄O₇²⁻−H₂O at 298 K. In the phase diagram, there are eleven univariant curves, five invariant points and seven crystallization regions saturated with Na₂B₄O₇ · 10H₂O, where the solids are Na₂SO₄, K₂SO₄, Na₂SO₄ · 3K₂SO₄ (Gla), Na₂SO₄ · 10H₂O, NaBr · 2H₂O, KBr and K₂B₄O₇ · 4H₂O. NaBr · 2H₂O has the highest concentration and strong salting-out effects on other salts.