The solubility of aspirin in four binary solvents of ethanol + methyl cyclohexane, n-propanol + methyl cyclohexane, acetone + methyl cyclohexane, and ethyl acetate + methyl cyclohexane was measured by the gravimetric method at temperatures from T = 283.15 to 323.15 K. The solubility of aspirin in all mixed solvents increased with the increase of temperature and decreased with the increase of the mole fraction of methyl cyclohexane. The solubility data of aspirin was correlated by the CNIBS/R–K model, Jouyban–Acree model, and nonrandom two-liquid (NRTL) model. Also, the average relative deviation (ARD) of all models was lower than 5%. The results indicated that these models fit the solubility data well. Besides, the mixing thermodynamic properties of aspirin in four binary solvent mixtures were investigated on the basis of the solubility data and the NRTL model. The results showed that the mixing process of aspirin is a spontaneous process and follows the increase of entropy principle.

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