Stearic acid solubility in mixed solvents of (water + ethanol) and (ethanol + ethyl acetate): Experimental data and comparison among different thermodynamic models

Abstract

In this study, the mole fraction solubility of stearic acid (SA) in ethanol, ethyl acetate and (water + ethanol) and (ethanol + ethyl acetate) solvents mixtures at atmospheric pressure from T = (298.15 to 330.15) K was estimated via a gravimetric method. The correlation of solubility data was performed with the van't Hoff, modified Apelblat and λh models in two binary solvent mixtures. While in mono-solvents, the van't Hoff, modified Apelblat, λh, Wilson, and NRTL models were employed. By comparing the models, we found that modified Apelblat equation and the van't Hoff equation fit the experimental data best. 5.94 × 10−2and 8.50 × 10−3 are the limit of the relative average deviation (RAD) as well as the root-mean-square deviation (RMSD) for the experimental and calculated solubility for the two binary solvent mixtures. Likewise, the dissolution enthalpy and dissolution entropy of stearic acid in the corresponding systems were predicted and the results demonstrated that the procedure for the dissolution in the mixed solvents is endothermic. The experimental solubility and mathematically calculated solubility can be usefully applied to the final crystallization and/or purification process of SA synthesis and to pharmaceutical formulation development of SA.