Densities, speeds Of Sound, and refractive indices of the binary mixtures Of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]) with acetone, methyl acetate, and ethyl acetate were experimentally measured over the whole range of compositions Lit T = (278.15 to 328.15) K and a pressure of 0.1 MPa. From these experimental data, excess molar volumes, excess isentropic compressibilities, molar refractions, and deviations in refractive indices have been calculated and fitted to an extended version of the Redlich-Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine-Flory-Patterson theory has been used to speculate on the cause of the volumetric variations for these Mixtures.