The densities of binary and ternary mixtures were measured for the system 1-ethyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide ([EMIM](+)[BETI](-)) + methanol or + acetone and [EMIM](+)[BETI](-) + methanol + acetone, respectively, at T = (298.15, 303.15, and 313.15) K, and the speed of sound data for the binary system 1-ethyl-3-methylimidazolium diethyleneglycol monomethylethersulfate ([EMIM](+)[CH(3)(OCH(2)CH(2))(2)OSO(3)](-)) + methanol were measured at T = 298.15 K. The excess molar volumes were calculated from the experimental densities and were fitted to the Redlich-Kister equation for the binary system. The excess molar volumes, V(m)(E), for the binary system ([EMIM](+)[BETI](-) + methanol) were positive for low mole fractions of methanol, and for the binary system ([EMIM](+)[BETI](-) + acetone), excess molar volumes were negative throughout the whole composition range. The ternary excess molar volumes were negative for all three temperatures. The isentropic compressibility for the binary system ([EMIM](+)[CH(3)(OCH(2)CH(2))(2)OSO(3)] + methanol) was negative over the entire composition range. The results have been interpreted in terms of the intermolecular interactions between the ionic liquid and the organic solvents.