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 x(methanol) > x(ethanol) > x(methyl) > x(ethyl). The experimental solubility data of the solutes (PA) in four pure solvents was correlated with the modified Apelblat equation and semiempirical Buchowski-Ksiazczak lambda h equation. Dissolution standard molar enthalpy Delta H-sol degrees (kJ.mol(-1)), Gibbs energy Delta(sol)G degrees (kJ center dot mol(-1)), and entropy Delta S-sol degrees (J center dot mol(-1) center dot K-1) of protocatechuic acid were estimated using the solubility data.