Solubility Measurement and Thermodynamic Correlation of 4-(Hydroxymethyl) Benzoic Acid in Nine Pure Solvents and Two Binary Solvent Mixtures at (283.15–323.15) K

The solubility of 4-(hydroxymethyl) benzoic acid (p-HMBA) in nine pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol, ethyl formate, ethyl acetate, isopropyl acetate, and butyl acetate) and two different binary solvents (methanol + water and ethanol + water) was measured by a gravimetric method at temperatures ranging from 283.15 to 323.15 K under atmospheric pressure (p = 0.1 MPa). The results reveal that the solubility of pHMBA increases with increasing temperature in all investigated solvents. Under an isothermal condition, the solubility of p-HMBA increases monotonously with the increase of the mole fraction of methanol in binary solvents of methanol and water. However, the solubility of p-HMBA increases first and then decreases with the increase of ethanol in the binary solvent mixtures of ethanol and water and reaches its maximum value when the mole fraction of ethanol is 0.8. The solubility data were correlated with the modified Apelblat equation and lambda h model. All of the models gave satisfactory correlation results. The results presented in this paper would be helpful to the further crystallization and separation process of p-HMBA.