Solid–liquid phase equilibrium and thermodynamic analysis of prothioconazole in mono-solvents and binary solvents from 283.15 K to 313.15 K

Solid-liquid phase equilibrium solubility of prothioconazole in seven mono-solvents and (2-propanol ± cyclohexane, 1-butanol ± cyclohexane) binary solvent mixtures was determined by gravimetric method from 283.15 K to 313.15 K at atmospheric pressure. The solubility of prothioconazole increased with increasing temperature in all tested solvents. In mono-solvents, the solubility values at a fixed temperature ranked as: 1-butanol > 1-propanol > 2-propanol > methanol > 2-butanol > acetonitrile > toluene. In binary solvent systems, the maximum solubility values were achieved at a certain solvent composition. The Apelblat equation, λh equation and NRTL model were employed to correlate the solubility data in mono-solvents, and the Apelblat equation in two binary solvent mixtures. The selected thermodynamic models can all give acceptable results. Furthermore, the apparent standard Gibbs free energy, enthalpy and entropy for the dissolution of prothioconazole were calculated, which indicates that the dissolution process of prothioconazole is an endothermic and entropy favorable process.