Volumetric behaviour of six ionic liquids from TÂ =Â (278 to 398)Â K and up to 120Â MPa

In this paper the volumetric behaviour of the ionic liquids 1-butyl-1-methylpyrrolidinium tetracyanoborate, 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, 1,3-dimethylimidazolium dimethylphosphate, 1-ethyl-3-methylimidazolium hexylsulfate, and trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate is reported. Density was measured over the temperature range (278.15 to 398.15) K up to 120 MPa by means of a high pressure densimeter based on the vibrating tube principle. Experimental values were correlated as a function of temperature and pressure by means of the Tammann-Tait equation obtaining standard deviations lower than 3 × 10−4 g · cm−3. From this correlation, isothermal compressibility and isobaric thermal expansivity are obtained by differentiation. Furthermore, two group contribution methods proposed by Gardas and Coutinho and by Jacquemin et al. are applied to these fluids to analyse their prediction abilities to determine densities, as well as an equation proposed by Kiselev et al. to obtain isothermal compressibility at 0.1 MPa.