Solubilities, Densities, Refractive Indices, and pH Values of the Aqueous Ternary Systems (LiCl + LiB5O8 + H2O) and (Li2SO4 + LiB5O8 + H2O) at 288.15 K and 101 kPa

Solubilities, densities, refractive indices, and pH values of the ternary systems (LiCl + LiB5O8 + H2O) and (Li2SO4 + LiB5O8 + H2O) at 288.15 K and 101 kPa were studied using the isothermal dissolution method and wet residue method. From the experimental data, the phase diagrams and the diagrams of the physicochemical properties including density, refractive index, and pH value against composition were plotted. The results show that the two systems belong to a simple saturation type, and no double salt or solid solution formed at 288.15 K. For the two systems, there are both in one invariant point, two isothermal dissolution curves, and two crystallization regions including lithium pentaborate pentahydrate (LiB5O8·5H2O, Lb5), lithium chloride dihydrate (LiCl·2H2O, Lc2, in the former), and lithium sulfate monohydrate (Li2SO4·H2O, Ls1, in the latter). It was found that the area of the crystallization region of Lb5 was larger than those of Lc2 in the former system and Ls1 in the latter system, and the results indicated that the solubility of lithium pentaborate was lower in the two systems. The densities and refractive indices in the two ternary systems at 288.15 K increased first and then decreased with the increase in LiCl and Li2SO4 concentrations in the solution. However, the pH values present a contrary trend, which decreased first and then increased. The calculated values of density and refractive index using empirical equations for the two ternary systems agree well with the experimental values.