Eutectic Temperature, Density, and Solubility of H3BO3–H2O, Na2B4O7–H2O, and NaBO2–H2O Binary Systems

This study aims to measure the solubility and binary eutectic point parameters (temperatures, densities, and compositions) of H3BO3–H2O, Na2B4O7–H2O, and NaBO2–H2O solid–liquid equilibrium systems. Eutectic temperatures were determined using multichannel thermometers equipped with high-precision Pt25 (±0.004 °C) sensors, whereas densities of the eutectic points were measured using a density meter equipped with an oscillating high-precision U-tube (±0.00005 g/cm3) sensor. Chemical compositions of the binary eutectic point samples were analyzed using an ICP-OES instrument. Eutectic parameters, that is, temperature, density, and composition of the H3BO3–H2O binary system were determined to be −0.61 ± 0.01 °C, 1.0114 ± 0.0005 g/cm3, and 2.37 ± 0.07 wt% respectively. Similarly, the same eutectic parameters were measured as −0.30 ± 0.01 °C, 1.0116 ± 0.0004 g/cm3, and 1.05 ± 0.06 wt% for the binary system of Na2B4O7–H2O, whereas eutectic parameters of the NaBO2–H2O binary system were found to be −6.11 ± 0.01 °C, 1.1823 ± 0.0004 g/cm3, and 13.40 ± 0.09 wt%.