Solubility measurement and thermodynamic model correlation of propyl gallate in pure and binary solvents from T = (293.15 to 333.15) K

Abstract

The solid−liquid equilibrium data of propyl gallate in nine pure solvents and binary solvent mixtures of ethanol + n-propanol were measured over the temperature range from (293.15 to 333.15) K by using a gravimetric method under atmospheric pressure. The experimental result proved that the rising temperature led to increased solubility of the propyl gallate in all selected solvents. For pure solvents, the solubility of propyl gallate increased according to the following order: ethanol < isobutanol < ethyl acetate < methanol < n-butanol < methyl acetate < isopropanol < n-propanol < acetone. For ethanol + n-propanol mixture solvents, the solubility of propyl gallate decreased with the increase of ethanol mass fraction. The experimental solubility in each selected solvent were correlated with a series of equations, including the modified Apelblat equation, Van't Hoff equation, λh equation, NRTL equation and Wilson equation. Computational results showed that all five selected models well fitted the experimental data. Hansen solubility parameters (HSP) were also applied to explain the solubility behavior of propyl gallate. In addition, the Van't Hoff equation was used to estimate the dissolution enthalpy (∆H°sol), dissolution entropy (∆S°sol) and Gibbs energy (ΔG°sol) of propyl gallate in selected solvents.