A volumetric and viscosity study for the mixtures of 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid with acetonitrile, dichloromethane, 2-butanone and N,N-dimethylformamide

The densities and viscosities for mixtures of 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid with acetonitrile, dichloromethane, 2-butanone and N,N-dimethylformamide have been determined at 298.15 K. From these measurements, it was found that viscosities of the mixtures can generally be described by an exponential equation. Their densities are linear functions of the mass fraction of the ionic liquid in the mixtures. These physical properties can be predicted as a function of the concentration of ionic liquid provided that the properties for pure components are known. The excess molar volume V-m(E) and the excess logarithm viscosities (ln eta)(E) were calculated and fitted to the Redlich-Kister polynomials. It is shown that the values of V-m(E) are negative but those of (ln eta)(E) are positive. Surprisingly, the minimum in V-m(E) and the maximum in (ln eta)(E) are observed at about the same mole fraction of the ionic liquid, xapproximate to0.3. The results are discussed in terms of the ion-dipole interactions between the cations of the ionic liquid and the organic solutes.