Thermophysical properties of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide at high temperatures and pressures

(p,ρ,T) data of ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [HMIM][NTf2] 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 are carried out with a newly constructed Anton-Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, aqueous NaCl solutions, methanol, toluene and acetone. An empiric equation of state for fitting of the (p,ρ,T) data of [HMIM][NTf2] has been developed as a function of pressure and temperature. This equation is used for the calculation of the thermophysical properties of IL, such as isothermal compressibility, isobaric thermal expansibility, thermal pressure coefficient, internal pressure, isobaric and isochoric heat capacities, speed of sound and isentropic expansibility.