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Thermodynamics of the aqueous sodium and potassium sulfate system at the temperature 200C and 400C

S.Attia-Essaies, L.Zayani, D.Ben Hassen-Chehimi, M.Trabelsi-Ayadi

The diagram of the ternary system Na+, K+/SO4 2- - H2O was established at 20°C and at 40°C by means of analytical measurements. In the equilibrium phase diagram of Na+, K+/SO4 2--H2O at 20°C there are two invariant points, three univariant curves and three regions of crystallization: K2SO4, Na2SO4.10H2O and NaK3(SO4)2. The compositions (%w/w) of the invariant points are respectively 5.41%ofNa2SO4/10.20%ofK2SO4 and 22.38%ofNa2 SO4/5.72% of K2SO4. At 40°C the system presents two invariant points, three univariant curves and three regions of crystallization containingK2SO4, Na2SO4 or NaK3(SO4)2.The composition (%w/w) of the invariant points are respectively 6.03%ofNa2SO4/12.82%ofK2SO4 and 30.65%ofNa2SO4/5.98% ofK2SO4.