A model for salty water-acetonitri le mixtures at 298.15 K was proposed based on three different contributions: chemical, physical and electrostatical. The first two were accomplished by ERAS model and the third was achieved by analyzing several proposals: Debye-Huckel, Hepler and a modified ERAS model. In order to test the model values, densities for the mixtures were measured with a vibrating-tube densimeter and the excess molar volumes were determined. The salts molar concentrations varied from 0.001 to 0.004, covering the entire composition range for water-acetonitrile. For each system, the three model approaches was applied. The modified ERAS model provides the best results. (C) 2011 Elsevier B.V. All rights reserved.