Measurement and Correlation of High-Pressure Densities and Atmospheric Viscosities of Ionic Liquids: 1‑Butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide), 1‑Allyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide, 1‑Ethyl-3-methylimidazolium Tetracyanoborate, and 1-Hexyl-3-methylimidazolium Tetracyanoborate

Four ionic liquids, [bmpyr]­[Tf2N] (1-butyl-1-methylpyrrolidinium bis­(trifluoromethylsulfonyl)­imide), [amim]­[Tf2N] (1-allyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide), [emim]­[TCB] (1-ethyl-3-methylimidazolium tetracyanoborate), and [hmim]­[TCB] (1-hexyl-3-methylimidazolium tetracyanoborate), were studied. High-pressure densities were measured at pressures up to 200 MPa and at temperatures of 312−433 K. Densities and viscosities at atmospheric pressure were measured over a temperature range of 293 to 373 K, and average relative deviation (ARD) of correlation with Vogel–Fulcher–Tammann equation for viscosity were within 0.08%. Correlation of the density data with the Tait equation could be obtained to within 0.02% ARD. Isobaric expansivities calculated from the Tait equation were constant or decreased slightly with increasing temperature in accordance with trends commonly reported for ionic liquids. Parameters for the ε*-modified Sanchez–Lacombe equation of state are tabulated that allow correlation of the ionic-liquid high-pressure densities to within an ARD of less than 0.08%.