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(p,ρ,T) data of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTf2] at T = (283.15 to 373.15) K and pressures up to p = 100 MPa are reported with an estimated experimental relative combined standard uncertainty of Δρ/ρ = ± (0.01 to 0.08) % in density. The measurements were carried out with a newly constructed Anton Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, toluene and aqueous NaCl solutions. An empiric equation of state for fitting of the (p,ρ,T) data of [EMIM][NTf2] has been developed as a function of pressure and temperature. This equation was used for the calculation of the thermal properties of IL, such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient, and internal pressure.

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The densities of five BMIMBF 4 (1-butyl-3-methylimidazolium tetrafluoroborate) + ethanol binary mixtures with compositions of (0.0701, 0.3147, 0.5384, 0.7452, and 0.9152) mole fraction BMIMBF 4 and of pure BMIMBF 4 have been measured with a vibrating-tube densimeter. Measurements were performed at temperatures from 298 K to 398 K and at pressures up to 40 MPa. The total uncertainty of density, temperature, pressure, and concentration measurements were estimated to be less than 0.1 kg · m −3 , 15 mK, 5 kPa, and 10 −4 , respectively. The uncertainties reported in this article are expanded uncertainties at the 95% confidence level with a coverage factor of k = 2. The measured densities were used to study derived volumetric properties such as excess, apparent, and partial molar volumes. It is shown that the values of excess molar volume for BMIMBF 4 + ethanol mixtures are negative at all measured temperatures and pressures over the whole concentration range. The effect of water content on the measured values of density is discussed. The volumetric (excess, apparent, and partial molar volumes) and structural (direct and total correlation integrals, cluster size) properties of dilute BMIMBF 4 + ethanol mixtures were studied in terms of the Krichevskii parameter. The measured densities were used to develop a Tait-type equation of state.

-Pressure-density-temperature (p,ρ,T) data of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf 2 ] at T = (273.15 to 413.15) K and pressures up to p =140 MPa are reported with an estimated experimental relative combined standard uncertainty of Δρ/ρ = ±(0.01 to 0.08)% in density. The measurements were carried out with a newly constructed Anton-Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, aqueous NaCl solution, methanol, toluene and acetone. An empirical equation of state for fitting the (p,ρ,T) data of [BMIM][NTf 2 ] has been developed as a function of pressure and temperature. This equation is used for the calculation of the thermophysical properties of the ionic liquid, such as isothermal compressibility, isobaric thermal expansibility, thermal pressure coefficient, internal pressure, isobaric and isochoric heat capacities, speed of sound and isentropic expansibility.

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