Study On The Metastable Equilibrium Of The Quinary System Li⁺, K⁺//CO₃^2-, SO₄^2-,B₄O₇^2--H₂O At 273K

An experimental study on metastable equilibria at 273 K in the quinary system Li⁺, K⁺//CO₃^2-, SO₄^2-, B₄O₇^2- -H₂O and it's subsystem Li⁺//CO₃^2-,SO₄^2-, B₄O₇^2--H₂O,K⁺//CO₃^2-,SO₄^2-, B₄O₇^2--H₂O and Li⁺, K //CO₃^2- SO₄^2- -H₂O were done by isothermal evaporation method. Metastable equilibrium solubilities and densities of the solution were determined experimentally. According to the experimental data, the metastable equilibrium phase diagrams and the density composition diagrams were plotted.The experimental results of the metastable equilibria show that the double salt K₂SO₄·Li₂SO₄ form in the quinary system Li⁺, K⁺//CO₃^2-, SO₄^2-, B₄O₇^2- -H₂O at 273K. In the metastable phase diagrams, the quinary system has four invariant points, nine univariant curves, six fields of crystallization (saturated with Li₂CO₃ ): LiBO₂·8H₂O, K₂B₄O₇·4 H₂O,K₂CO₃·3/2H₂O,K₂SO₄,K₂SO₄·Li₂SO₄ and Li₂ SO₄·H₂O.The metastable phase diagram of system Li // CO₃^2-SO4^2-, B₄O₇^2- -H₂O is simple total saturated type. The metastable phase diagram of the quaternary system has one invariant point, three univariant curves, three fields of crystallization: Li₂CO₃, Li₂SO₄·H₂O, LiBO₂·8H₂O. The salt LiBO₂·8H₂O has the largest crystallization field. The salt Li₂SO₄·H₂O has the smallest crystallization field.The metastable phase diagram of system K⁺// CO₃^2-,SO₄^2-, B₄O₇^2- -H₂O is simple total saturated type. The metastable phase diagram of the quaternary system has one invariant point, three univariant curves, three fields of crystallization :K₂CO₃·3/2H₂O, K₂SO₄, K₂B₄O₇·4H₂O. The salt K₂SO₄ has the largest crystallization field. The salt K₂CO₃·3/2H₂O has the smallest crystallization field.The double salt K₂SO₄·Li₂SO₄ form in the quaternary system Li⁺, K⁺//CO₃^2-, SO₄^2- -H₂O at273K.In the metastable phase diagram, the quaternary system has three invariant points, seven univariant curves, five fields of crystallization:K₂SO₄, Li₂SO₄·H₂O, Li₂CO₃ , K₂CO₃·3/2H₂O and double salt K₂SO₄·Li₂SO₄. The salt K₂CO₃·3/2H₂O has the smallest crystallization field. The salt Li₂CO₃ has the largest crystallization field.Using the solubilities data of quaternary systems at 273K, the single salt ion-interaction parameters and corresponding ion-interaction mixing parameters for Pitzer's equations were fitted by multiple linear regression methoed. Equilibrium constant of salts for liquid+solid equilibrium at 273K were evaluated with Pitzer's model . The solubilities of quinary system were calculated with Pitzer's equations. Corresponding discussion of prediction results was finished.