Solubility of Gallic Acid, Vanillin, Syringic Acid, and Protocatechuic Acid in Aqueous Sulfate Solutions from (293.15 to 318.15) K

The solubility of gallic acid, vanillin, syringic acid, and protocatechuic acid in aqueous solutions of various concentrations of sodium sulfate was determined from (293.15 to 318.15) K at atmospheric pressure using a thermostatted reactor and HPLC analysis. Results showed a salting-out effect on the solubility of the tested phenolic compounds. The solubility data were accurately correlated to a semiempirical equation. The temperature dependence of the solubility data were used to estimate thermodynamic properties such as Gibbs free energy (Δsol G o), molar enthalpy of dissolution (Δsol H o), and molar entropy of dissolution (Δsol S o).