The influence of the extraction conditions on the distribution coefficient of m-cresol were investigated. The equilibria of m-cresol extraction from an aqueous solution by the tri-n-octylamine sulfate salts (TOA salts) in an organic solvent were examined. Sulfuric acid first reacted with tri-n-octylamine (TOA) to form TOA salts; then m-cresol was extracted into the organic phase from the aqueous phase by the TOA salts. The model of the equilibrium of the chemical reaction of TOA and sulfuric acid to form the TOA salts was constructed by modifying the Wilson model (Wilson, 1967). The predictions of the developed model were fairly consistent with the experimental data, and it was applied to the reaction systems in benzene at various temperatures to predict the extraction of m-cresol. The number of water molecules associated with the various TOA salts, which reflect the extraction capability of m-cresol, was determined.