Solubility Behavior of Salicylic Acid in Aqueous Alcohol Mixtures: Interplay of Temperature, Solvent Composition, and Thermodynamic Modeling.

Salicylic acid is widely used in pharmaceutical and cosmetic applications, where reliable solubility data are critical for optimizing crystallization-based purification processes. While literature reports values for neat solvents, comprehensive measurements in binary water-alcohol mixtures over the full composition range remain scarce. In this work, the mole fraction solubility of salicylic acid was experimentally determined in the binary mixtures of water + methanol, water + ethanol, and water +2-propanol over the entire solvent composition range at temperatures from 283.2 to 323.2 K at atmospheric pressure using a gravimetric method. The experimental data were analyzed using analytical solutions of groups (ASOG), PC-SAFT, and PSRK thermodynamic models to describe the solid-liquid equilibrium behavior. PC-SAFT showed the best overall performance, yielding the lowest deviations, followed by PSRK and ASOG. The solubility increases monotonically with temperature in all systems, indicating an endothermic dissolution process. In mixed solvents, the solubility decreases sharply with an increasing water mole fraction, supporting the antisolvent effect of water. This behavior is associated with solvent polarity and specific solute-solvent interactions. Alcohols act as effective cosolvents, increasing solubility as the solvent polarity decreases. The new data sets fill important gaps in the literature and provide a consistent basis for thermodynamic modeling, supporting the improved design of crystallization and separation processes involving salicylic acid.