The solubility of sorafenib free base (SFB) and sorafenib tosylate (ST) in five monosolvents and binary solvents of 2-propanol + 1,4-dioxane was measured over the temperature ranged from 283.15 to 333.15 K by using a UV spectroscopy method. The solubility of SFB and ST in different monosolvents increases with increasing temperature, while in the binary solvents, the solubility shows the maximum value at 0.50 and 0.75 2-propanol mole fraction for SFB and ST, respectively. The Apelblat model and the CNIBS/R-K model were applied to correlate the solubility data, which shows that the two selected thermodynamic models could give satisfactory results. Moreover, mixing thermodynamic properties of enthalpy, entropy, and Gibbs free energy of SFB and ST were obtained based on the nonrandom two-liquid model for further understanding of the mixing behavior.

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