Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Solubilities and physicochemical properties (density and refractive index) for the ternary system (Na+//SO42-, BO2- - H2O) at (288.15 and 308.15) K and 101.325 kPa were studied by isothermal dissolution equilibrium method. Phase diagrams and diagrams of the physicochemical properties (density and refractive index) were plotted against the concentration of sodium sulfate. For both temperatures, the phase diagrams contained one invariant point, two univariant curves, and two crystallization regions corresponding to sodium metaborate tetrahydrate (NaBO2*4H2O, Nb) and mirabilite (Na2SO4*10H2O, Mir) at 288.15 K, and Nb and thenardite (Na2SO4, Th) at 308.15 K, respectively. The area of the crystallization region of sodium metaborate tetrahydrate was enlarged with increasing of temperature, and the solid phase of mirabilite transformed into the thenardite when the temperature increases from 288.15 K to 308.15 K. The physiochemical properties including density and refractive index of the system at (288.15 and 308.15) K were similarly increased first and decreased later with increasing of sodium sulfate concentration in the equilibrium solution. The experimental data for the density and refractive index were correlated by the empirical equations, and the calculated and the experimental values agreed well.