Densities, speeds of sound, and refractive indices of the binary mixtures of BMIM PF6 (1-butyl-3-methyl imidazolium hexafluorophosphate), HMIM PF6 (1-hexyl-3-methylimidazolium hexafluorophosphate), OMIM PF6 (1-methyl-3-octylimidazolium hexafluorophosphate), and MMIM CH3SO4 (1,3-dimethylimidazolium methyl sulfate) with 2-butanone, ethylacetate, and 2-propanol were determined from (293.15 to 303.15) K. Excess molar volumes, changes of refractive index on mixing, and deviations in isentropic compressibility were calculated for the above systems. The liquid−liquid equilibrium data of the binary mixtures ionic liquid + 2-propanol were carried out, and they were compared with the correlated values obtained by means of the NRTL and UNIQUAC equations.