The osmotic virial model and the Flory-Huggins model, with the Debye-Huckel equation as an electrostatic term, have been used to correlate the liquid-liquid equilibrium data for an aqueous solution of polyoxyethylene cetyl ether surfactant (abbreviated as Brij 58) and three inorganic salts (containing NH4H2PO4, (NH4)(2)HPO4, and Brij58-KH2PO4) at 298.15 K. The results have shown that the maximum absolute deviation from experimental data is less than 0.6% and 1.4% for the osmotic virial model and the Flory-Huggins theory, respectively. These models are in good agreement with experimental data.