Solid-liquid equilibrium solubility, thermodynamic properties, and solvent effect of flavoxate hydrochloride in twelve pure solvents ranged from 278.15 K to 323.15 K

The mole fraction solubility data of flavoxate hydrochloride in twelve experimentally selected solvents were measured at atmospheric pressure by the laser monitoring method. The experimental temperature range was 278.15 to 328.15 K. The solubility of flavoxate hydrochloride showed a nonlinear increase with temperature increase. At a fixed experimental temperature, the order of solubility is: ethylene glycol > methanol > 2-methoxyethanol ≈ dimethyl sulfoxide >  N -Methyl-2-pyrrolidone > water > 2-propoxyethanol > 2-ethoxyethanol > ethanol >  n -butanol >  n -propanol > acetonitrile. Also, solubility data were correlated by two semi-empirical models and three activity coefficient models. From the average relative deviation and root mean square deviation data of the five models, it can be seen that the Modified Apelblat model has the best correlation. Furthermore, in this work, the effect of solvent on the solubility of flavoxate hydrochloride was analyzed using the KAT-LSER model. Furthermore, the thermodynamic parameters (Δ dis G 0 , Δ dis H 0 , Δ dis S 0 ) of the dissolution process of flavoxate hydrochloride were calculated by the Van’t Hoff model. The data indicate that the dissolution process of flavonoid hydrochloride in twelve experimentally selected solvents is endothermic and entropy-driven.