Measurement and correlation for solubilities of isophthalic acid and m-toluic acid in binary acetic acid + water and acetic acid + m-xylene solvent mixtures

In this study, the solubilities of isophthalic acid (IPA) and m-toluic acid (m-TA) in binary acetic acid (HAc) + (water or m-xylene) solvent mixtures were measured by using a synthetic method at atmospheric pressure. The mole fraction of HAc in the corresponding solvent mixtures ranges from 0.0000 to 1.000. The measured data show that within the temperature range studied, the solubilities of IPA and m-TA increase with increasing temperature at constant solvent composition. At a given temperature, the solubilities of IPA and m-TA decrease with the decreasing mole fraction of HAc in HAc + water solvent mixtures; whereas the “maximum-solubility effect” was observed in HAc + m-xylene solvent mixtures, and that with the mole fraction of HAc at 0.8761 has the best dissolving capacity for IPA at constant temperature. The experimental solubilities were well correlated by both the nonrandom two-liquid (NRTL) and Apelblat equations, and the calculated solubilities agree satisfactorily with the measured results. Furthermore, the thermodynamic functions including dissolution enthalpy, entropy and Gibbs energy were obtained from the solubility data by using the van't Hoff equation.153