(R,S)-Mandelic acid in pure and binary solvents solubility measurement and its correlation with thermodynamic models

Abstract

In this study, The solubility of (R,S)-mandelic acid in different solvents, including mono-solvent (H2O, methanol, ethanol, n-propanol, isopropanol) and binary solvents (methanol + H2O, ethanol + H2O, n-propanol + H2O, isopropanol + H2O, n-butanol + H2O), using analytical stirred-flask method and weight analysis method to determine the compositions of the saturated solutions at the atmospheric pressure. We found that the experimental solubility values increased with the rising of temperature accordingly. The experimental solubilities were correlated by the Ideal model, Apelblat model, λh (Buchowski) model, Wilson model, NRTL model. The results have shown that the Wilson model is the best model, which correlates the solubility of (R, S)-mandelic acid in the mono-solvent and binary solvents and fits well with experimental data. In addition, the thermodynamic properties of dissolution were calculated according to Van’t Hoff equation and experimental solubility, including Gibbs energy, entropy and enthalpy. The result confirms that the dissolution process in all solvents is always endothermic and entropy driven.