Volumetric and Speed of Sound of Ionic Liquid, 1-Butyl-3-methylimidazolium Hexafluorophosphate with Acetonitrile and Methanol at T = (298.15 to 318.15) K

We report the density (ρ) and speed of sound ( u ) data for 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) + methanol and ([BMIM][PF 6 ]) + acetonitrile binary mixtures over the entire range of their compositions at T = (298.15 to 318.15) K. From these data, excess molar volume and isentropic compressibility deviation values have been calculated and fitted to the fourth-order Redlich−Kister equation. The excess molar volume values ( V E ) for acetonitrile mixtures are more negative than methanol mixtures. Isentropic compressibility deviation values (Δκ s ) in methanol mixtures are more than acetonitrile mixtures. The results have been interpreted in terms of ion−dipole interactions and structural factors of the ionic liquid and these organic solvents.