Experimental Measurement and Correlation of Solubility Data and Thermodynamic Properties of Protocatechuic Acid in Four Organic Solvents

Abstract

Using a thermostated reactor and UV/vis spectrophotometer analysis, the solubility of protocatechuic acid (PA) in ethanol, methanol, methyl acetate, and ethyl acetate was measured from (293.15 to 318.15) K at atmospheric pressure. The effect of solvent type and temperature on the solubility are discussed. The relative solubility of protocatechuic acid in different solvents was determined in descending order to be xmethanol > xethanol > xmethyl > xethyl. The experimental solubility data of the solutes (PA) in four pure solvents was correlated with the modified Apelblat equation and semiempirical Buchowski–Ksiazczak λh equation. Dissolution standard molar enthalpy ΔsolH° (kJ·mol–1), Gibbs energy ΔsolG° (kJ·mol–1), and entropy ΔsolS° (J·mol–1·K–1) of protocatechuic acid were estimated using the solubility data: