| Abstract
| - The viscosity of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) has been measuredbetween (0 and 80) °C with a falling-body viscometer. High-pressure measurements were made at (10, 25, 50,and 75) °C to a maximum pressure of 300 MPa. The expanded uncertainty is estimated at ± 2 %. ModifiedLitovitz and Vogel−Fulcher−Tammann (VFT) equations are used to represent the temperature and pressuredependence. The Angell equation relating the strength parameter D, the VFT parameter T0, and the glass temperatureTg is again confirmed. Comparing D for the salts [BMIM]PF6, [HMIM]PF6, [OMIM]PF6, [BMIM]BF4, [OMIM]BF4, and [BMIM][Tf2N], we find D([BMIM]+) < D([HMIM]+) < D([OMIM]+) where the anion is common andD([Tf2N]-) < D(BF4-) < D(PF6-) where the cation is common. Densities and thermal expansivities between (0and 90) °C at atmospheric pressure with overall uncertainty estimated at ± 0.000 05 g·cm-3 and ± 0.02·10-3K-1 are also reported. The densities are compared with our previously published values for [BMIM]PF6, [HMIM]PF6, [OMIM]PF6, [OMIM]BF4, and [BMIM][Tf2N].
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