Densities and thermal conductivities of ionic liquids, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-octyl-3-methylimidazolium bromide, at pressures up to 20 MPa

Density and thermal conductivity values are reported for 1-hexyl-3-methylimidazolium chloride ([HMIM][ Cl]), 1-octyl-3-methylimidazolium chloride ([OMIM][Cl]), and 1-octyl-3-methylimidazolium bromide ([OMIM] [Br]) ionic liquids (ILs). The densities were measured using a vibrating tube densimeter over the temperature range 293-353 K, at pressures <= 20 MPa. The combined standard uncertainty in density was estimated to be 0.1%. The transient short hot-wire method was used to measure the thermal conductivities over the temperature range 294-335 K at pressures <= 20 MPa. The combined standard uncertainty in thermal conductivity is estimated to be 3.0% for [HMIM][Cl] and [OMIM][Cl], and 4.8% for [OMIM][Br]. The measured densities agreed with some of the available literature values, within their experimental uncertainties. The thermal conductivities of these halide-type ILs are in the same range as those of other ILs and have a very small temperature and pressure dependence as it is for other ILs. The deviations of the experimental values at 293.15 K and 0.1 MPa from the predicted values proposed by Koller et al. were in good agreement for these three ILs.