Solubility of Gallic Acid, Catechin, and Protocatechuic Acid in Subcritical Water from (298.75 to 415.85) K

Abstract

The solubility of gallic acid hydrate, protocatechuic acid, and (+)-catechin hydrate was measured between 298.75 K and 415.85 K using a dynamic flow apparatus. The aqueous solubility of gallic acid hydrate was found to vary between 12.6 g·L−1 at 298.75 K and 2870 g·L−1 at 415.85 K. The aqueous solubility of protocatechuic acid at the same temperatures varied between 29.4 g·L−1 and 1180 g·L−1, respectively, while that of (+)-catechin hydrate varied between 2.26 g·L−1 and 576 g·L−1, respectively. The aqueous solubility of the phenolic compounds was found to increase exponentially with temperature. The temperature dependence of the aqueous solubility of the phenolic compounds was estimated using empirical correlations based on the data presented in this work. The thermodynamic properties such as standard molar enthalpy, standard molar entropy, and standard molar Gibbs energy of solution were also calculated from the solubility data.