Experimental density measurements are reported, and the derived thermodynamic properties, such as the isothermal compressibility, the isobaric expansivity, and the thermal pressure coefficient are presented as Supporting Information for several imidazolium-based ionic liquids (ILs), namely, 1-ethyl-3-methyl-imidazolium bis-(trifluoromethylsulfonyl)imide [C 2 mim][NTf 2 ], 1-heptyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C 7 mim][NTf 2 ], 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C 8 mim][NTf 2 ], 1-ethyl-3-methylimidazolium tetrafluoroborate [C 2 mim][BF 4 ], and 1-butyl-3-methyl-imidazolium tricyanomethane [C 4 mim][C(CN) 3 ] in the pressure (0.10 < p/MPa < 30.00) and temperature (293.15 < T/K < 393.15) domains. These ILs were chosen to provide an understanding of the influence of the cation alkyl chain length and the anion influence on the properties under study. Experimental densities are correlated with the Tait equation with an average absolute deviation (AAD) less than 0.04 %. Experimental densities are in good agreement with the densities obtained by some recent predictive methods proposed in the literature.

This work addresses the experimental measurements of the pressure (0.10 < p/MPa < 10.0) and temperature (293.15 < T/K < 393.15) dependence of the density and derived thermodynamic properties, such as the isothermal compressibility, the isobaric expansivity, the thermal pressure coefficient, and the pressure dependence of the heat capacity of several imidazolium-based ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium tetrafluoroborate, [ . These ILs were chosen to provide an understanding of the influence of the cation alkyl chain length, the number of cation substitutions, and the anion influence on the properties under study. The influence of water content in the density was also studied for the most hydrophobic IL used, [omim]- [PF 6 ]. A simple ideal-volume model was employed for the prediction of the imidazolium molar volumes at ambient conditions, which proved to agree well with the experimental results.

In the present work, experimental density measurements are reported along with the derived thermodynamic properties, such as the isothermal compressibility (κ T ), the isobaric expansivity (R p ), and the thermal pressure coefficient (γ V ) for imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based ionic liquids (