Solid-Liquid Phase Equilibria in the Aqueous System Containing Potassium,Magnesium,and Borate at 308.15 K

Experimental studies on the solubility, density, refractive index, and pH value in the aqueous system containing potassium, magnesium, and borate at 308.15 K were determined with the method of isothermal dissolution equilibrium. Based on the experimental results, the diagrams of solubility, density, refractive index, and pH value in this system were plotted. We found that there were one eutectic point and two crystallization regions corresponding to the large area of inderite (L + Mg2B6O11·15H2O) and the relatively small area of potassium borate tetrahydrate (L + K2B4O7 ·4H2O), respectively. Neither double salt nor solid solution was found in this system. The physicochemical properties (density, refractive index, and pH value) in solution at 308.15 K changed regularly with increasing potassium borate concentration. The calculated values of density and refractive index using empirical equations of the aqueous system were in good agreement with the experimental values.