Densities and speeds of sound for aqueous solutions of ionic liquids having 1-butyl-3-methylimidazolium as cation and chloride, bromide, iodide, acetate, tetrafluoroborate, and trifluoromethanesulfonate as anions were accurately measured at various concentrations and temperatures. The data were used in evaluating thermodynamic properties as apparent molar volumes and apparent molar isentropic compressions. Infinite dilution values of these properties were determined using appropriate extrapolation procedures utilizing Debye-Huckel limiting law for electrolyte solutions. Apparent molar isobaric expansions at infinite dilutions were also evaluated from the temperature dependence of apparent molar volumes. The results were interpreted in terms of ionic liquid-water interactions. (C) 2012 Elsevier Ltd. All rights reserved.