In this work liquid-liquid equilibria (LLE) in the system containing 1-butanol-water-sodium nitrate at temperatures of 25 and 35 degrees C has been investigated experimentally and theoretically. The extended UNIQUAC model has previously been used for correlation of liquid-liquid equilibrium in aqueous salt systems containing alcohols. In that model the excess Gibbs energy consists of two terms, the original UNIQUAC term and Debye-Huckel term which considers the alcohol as a non-electrolyte solute. In this work, a modified extended UNIQUAC model is used by taking into account mixed solvent theories. The model consists of three terms, the original UNIQUAC term, a Pitzer-Debye-Huckel term and a Born term. The model has been found to give a satisfactory description of LLE data obtained in this work, with an average absolute deviation of less than 0.5 in calculated mass percent compared to experimental data. (C) 2010 Elsevier B.V. All rights reserved.