By using the synthetic method, the solubilities 120 of benzoic acid in binary methylbenzene + benzyl alcohol Solvent mixtures at (301.05 to 355.65) K and in binary: methylbenzene + benzaldehyde solvent mixtures at (301.05 to 354.45) K were determined at atmospheric pressure. The Studied mass fractions of benzyl alcohol and benzaldehyde in the corresponding binary solvent mixtures range from 0.0 to 1.0. It was found that the measured solubilities increase with the increase of temperature at constant solvent composition. For the ternary system benzoic acid + methylbenzene + benzyl alcohol; the results show that the binary methylbenzene + benzyl alcohol-solvent mixture with the mass fraction of benzyl alcohol at 0.80 has the best dissolving capacity for benzoic acid at constant temperature. However, for the ternary system benzoic acid + methylbenzene + benzaldehyde, the results show that the binary methylbenzene + benzaldehyde solvent mixture with the mass fraction of benzaldehyde of 0.20 has the best dissolving capacity for benzoic acid at constant temperature. The experimental data were correlated by both the nonrandom two-liquid (NRTL) and the Apelblat equations, and the correlated solubilities agree satisfactorily with the experimental observations. By coupling the Apelblat equation with the Clark and Glew equation, the thermodynamic functions for the two studied solid liquid equilibrium systems, including dissolution enthalpy, entropy, Gibbs energy, and isobaric heat capacity, were calculated and discussed.