Densities and speeds of sound and their excess properties for 1-butyl-3- methylimidazolium Hexafluorophosphate (Bmim) (PF6) with 1-Butanol over the entire range of mole fraction are reported at temperature 303.15 K and atmospheric pressure. Isentropic and excess isentropic compressibility for ionic liquid with 1-Butaanol were calculated from the experimental results. The excess values are fitted to the Redlich−Kister polynomial equation to estimate the binary coefficients and standard error between the experimental and calculated values. The measured speeds of sound were compared to the values obtained from Schaaffs' collision factor theory, Jacobson's intermolecular free length theory of solutions and Nomoto’s relation. In addition, the experimentally obtained refractive indices were compared to the calculated values using Lorentz-Lorenz, Dale-Gladstone and Eykman mixing rules. The theoretical results obtained from these relations fairly agrees within the experimental precision. Further, the molecular interactions involved in IL binary mixture system were studied.
