New measurements have been made for the viscosity of the room-temperature ionic liquid 1-butyl- 3-methylimidazolium hexafluorophosphate ([BMIM]PF6) between (0 and 80) °C with a falling-body viscometer. High-pressure measurements were made at (25, 35, 50, 60, and 70) °C. The overall uncertainty is estimated at ± (2 to 3) %. Atmospheric pressure densities obtained with a vibrating tube densimeter are also reported for temperatures between (0 and 90) °C with an overall uncertainty estimated at ± 0.00005 g·cm-3. The viscosity behavior is qualitatively different from that of molecular liquids, with isotherms being best fitted as functions of the applied pressure rather than as functions of the molar volume. Modified Litovitz and Vogel−Fulcher−Tammann equations have been used to incorporate both the temperature and pressure dependence. Interestingly, the T 0 parameter of the VFT equation appears to be independent of pressure within the state point range of the data, but the Angell strength parameter increases with increasing pressure.

The viscosities of the ionic liquids 1-methyl-3-hexylimidazolium hexafluorophosphate, [HMIM]PF6, and 1-butyl-3-methylimidazolium bis(trifluorosulfonyl)imide, [BMIM][Tf2N], have been measured between (0 and 80) °C and at maximum pressures of 238 MPa ([HMIM]PF6) and 300 MPa ([BMIM][Tf2N]) at 75 °C with a falling-body viscometer. The overall uncertainty is estimated at ± 2 %. Modified Litovitz and Vogel−Fulcher−Tammann (VFT) equations are used to represent the temperature and pressure dependence. The Angell equation relating the strength factor D, the VFT parameter T 0, and the glass temperature T g is confirmed. Densities between (0 and 90) °C at atmospheric pressure with an overall uncertainty estimated at ± 0.000 05 g·cm-3 are also reported.

The viscosities of the ionic liquids 1-methyl-3-octylimidazolium hexafluorophosphate, [OMIM]PF6, and 1-methyl-3-octylimidazolium tetrafluoroborate [OMIM]BF4, have been measured between (0 and 80) °C and at pressures to 176 MPa ([OMIM]PF6) and 224 MPa ([OMIM]BF4) with a falling-body viscometer. The overall uncertainty is estimated at ± (2 to 3) %. Modified Litovitz and Vogel−Fulcher−Tammann equations are used to represent the temperature and pressure dependence. The T 0 parameter for the latter is found to be consistent with Angell's relationship linking T 0 and the strength parameter D with the glass temperature T g. Densities between (0 and 90) °C at atmospheric pressure are also reported for both substances. These have an overall uncertainty estimated at ± 0.00005 g·cm-3. The in-built viscosity correction for the Anton-Paar DMA5000 densimeter was confirmed using high-viscosity reference standards to an upper limit of 16 Pa·s.