Thermodynamic properties of betulinic acid in THF + water mixed solvents at different temperatures

• The solubilities of betulinic acid in the THF + water were determined at different temperatures.
• The highest solubility value is obtained in the pure THF.
• The thermodynamic properties of the solution process and the crystal habit of betulinic acid were discussed.

The solubilities of betulinic acid in binary solvent mixtures of THF + water in the temperature range of (278.2–318.2) K were determined by an analytical method. The solubility of betulinic acid in a binary solvent mixture increased with the increase of molar fraction of THF and the temperature. The solubilities data were correlated with a semi-empirical equation. The calculated solubilities showed good agreement with the experimental data. According to the Van’t Hoff equation and the Gibbs equation, the thermodynamic properties for the solution process including Gibbs energy, enthalpy, and entropy were obtained. The crystal habit of betulinic acid changes in morphology at different solvent mixtures was observed using SEM.