Thermodynamics of solubility of isatin in Carbitol + water mixed solvent systems at different temperatures

Thermodynamics of solubility of natural pharmacologically active compound isatin in various Carbitol + water mixed solvent systems was studied. The solubilities of isatin were measured at T = (298.15 to 338.15) K at atmospheric pressure using an isothermal method. The measured solubility data of isatin was correlated and regressed by three semiempirical models. The values of root mean square deviations were observed less than 0.040 by all three semiempirical models. The mole fraction solubility of natural isatin was found to be highest in pure Carbitol (5.20 × 10− 1 at 298.15 K) and lowest in pure water (5.13 × 10− 5 at 298.15 K) at T = (298.15 to 338.15) K. The resulting data of Van't Hoff and Krug analyses showed an endothermic, spontaneous and an entropy-driven dissolution of isatin in all Carbitol + water mixed solvent systems.