Measurement and Correlation of Solubility of Benzothiazolium Ionic Liquids in Ethanol + Ethyl Benzoate YaoTian DuKaifeng 2020 The solubilities of benzothazolium-based ionic liquids (ILs) [HBth]­[BF<sub>4</sub>], [HBth]­[CH<sub>3</sub>SO<sub>3</sub>], and [HBth]­[<i>p</i>-TSA] in binary ethanol + ethyl benzoate solvents were measured using the equilibrium method with the temperature range from 233.2 to 293.7 K at atmospheric pressure. Results of these measurements were correlated by both λ<i>h</i> equation and the modified Apelblat equation. It was found that both models gave satisfactory correlation results. In the λ<i>h</i> model, the average relative deviations were 0.7145, 0.7845, and 0.8119% for [HBth]­[BF<sub>4</sub>], [HBth]­[CH<sub>3</sub>SO<sub>3</sub>], and [HBth]­[<i>p</i>-TSA], respectively. Interestingly, the parameters of λ and <i>h</i> for the λ<i>h</i> model and <i>A</i>, <i>B</i>, and <i>C</i> for the modified Apelblat model were simultaneously expressed as functions of solvent composition (<i>x</i><sub>sol</sub>) for the first time. Furthermore, solubilities of these three ILs in the binary system were predicted through these two sets of self-created correlation equations with ideal performances. The total average relative deviations were less than 2.2% for both models. These successful in-depth correlations and validated prediction results have guaranteed the accuracy of experimental solubility data and provide us a reliable method for accurate solubility prediction at any temperature with any solvent composition. This developed calculation method in this report lays a foundation for accurate industrial recovery of ILs and gives us valuable guidance for the design of the specific purification process to acquire desired purity of the product in industrial production.