Density, Speed of Sound, and Derived Thermodynamic Properties of Ionic Liquids [EMIM]+[BETI]− or ([EMIM]+[CH3(OCH2CH2)2OSO3]− + Methanol or + Acetone) at T = (298.15 or 303.15 or 313.15) K

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.