Thermodynamic models for determination of the solubility of sulfanilic acid in different solvents at temperatures from (278.15 to 328.15) K

Data on corresponding solid-liquid equilibria of sulfanilic acid in different organic solvents are essential for industrial design and further theoretical studies. In this study, the solubilities of sulfanilic acid were measured in methanol, ethanol, 2-propanol, acetone, acetonitrile, formic acid, and acetic acid with the temperature range of (278.15 to 328.15) K by the analytical stirred-flask method under atmospheric pressure. For the temperature range investigated, the solubility of sulfanilic acid in the solvents increased with increasing temperature. The thermodynamic models, such as the van't Hoff model, the modified Apelblat model, and the Buchowski-Ksiazaczak λh model were investigated to describe the experimental data. It was found that the modified Apelblat model was the most suitable for predicting the solubility behavior of sulfanilic acid with increasing temperature. The calculated thermodynamic parameters indicated that in each studied solvent the dissolution process of sulfanilic acid is endothermic.