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With the isothermal dissolution equilibrium method and wet-residue method, the solubility data as well as physicochemical properties including density, refractive index, and pH value of the two ternary systems (NaCl + NaBO 2 + H 2 O) and (Na 2 SO 4 + NaBO 2 + H 2 O) at 298.15 K and 0.1 MPa have been experimentally determined, and the relatively phase diagrams have been established for the first time. In the ternary system (NaCl + NaBO 2 + H 2 O), two invariant points, three univariant curves, and three crystallization regions corresponding to sodium chloride (NaCl), sodium metaborate tetrahydrate (NaBO 2 •4H 2 O), and a congruent double salt teepleite (NaCl•NaBO 2 •2H 2 O) were detected. While in the ternary system (Na 2 SO 4 + NaBO 2 + H 2 O), there are one invariant point, two univariant curves, and two crystallization regions corresponding to NaBO 2 •4H 2 O and mirabilite (Na 2 SO 4 •10H 2 O). The physicochemical properties (density, refractive index, and pH value) in the two systems present a regular variation versus that with the changes of sodium metaborate concentration in the solution. Moreover, on the basis their empirical equations, the calculated values of refractive index and density are consistent with the experimental data.

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Solubilities and physicochemical properties (density and refractive index) for the ternary system (Na+//SO4 2–, BO2 –-H2O) at (288.15 and 308.15) K and 101.325 kPa were studied by the 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 the increase of temperature, and the solid phase of mirabilite transformed into thenardite when the temperature increased from 288.15 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 the increase of sodium sulfate concentration in the equilibrium solution. The experimental data of the density and refractive index were correlated using the empirical equations, and the calculated and experimental values agreed well.