Solubility and thermodynamic studies of procaine hydrochloride in propylene glycol + 2-propanol binary mixtures at different temperatures

In the present work, the solubility of procaine-HCl was determined in propylene glycol (PG) +2-propanol mixtures at temperatures of 298.2–313.2 K. The maximum solubility of procaine-HCl in mole fraction unit was 1.84 × 10 −2 in neat PG at 313.2 K and the minimum solubility was 3.55 × 10 −4 in neat 2-propanol at 298.2 K. The experimental solubility data were correlated with some linear and non-linear cosolvency models ( i.e. , the van't Hoff, the Jouyban-Acree, the Jouyban-Acree- van't Hoff and modified Wilson) and their accuracy was investigated with the mean relative deviations of the back-calculated solubility data against experimental values. The results showed a high accuracy with MRDs % <7.0 % for the investigated models. Moreover, for thermodynamic studies, the Gibbs energy, enthalpy, and entropy were calculated utilizing the van't Hoff and Gibbs equations. It should be noted that this study provides, for the first time, the determination of experimental solubility data for procaine-HCl in PG + 2-propanol.