New experimental data on the density of 1-butyl-3-methylimidazolium tetrafluoroborate are reported, obtained with a constant-volume apparatus described here in detail. The measurements were conducted along eight isochores at temperatures from (354 to 240) K and at nominal pressures of 1 MPa and from (10 to 60) MPa with a 10 MPa step. The combined uncertainty at the 95 % confidence level of a density measurement is estimated to be less than 1 kg·m−3, i.e., 0.1 %. A Tait-type equation was developed describing the ρ(T, p) dependence. The equation is fitted to the data of the present work and to critically assessed data of other authors compiled from the literature. Values of the coefficient of isothermal compressibility and of isobaric thermal expansion for 1-butyl-3-methylimidazolium tetrafluoroborate were calculated from the correlation equation and compared with experimental data from the literature. An unusual decreasing dependence of the isobaric thermal expansion coefficient on temperature, observed by other authors, was confirmed.
Simple but highly accurate correlations have been developed for the thermodynamic properties (including density, heat capacity, and speed of sound), viscosity, thermal conductivity, and static dielectric constant of liquid water as a function of temperature at a pressure of 0.1MPa. The calculations may be simply extended to a pressure range from the saturation pressure to 0.3MPa. The temperature range covered in most cases is from 253.15to383.15K; this includes some temperatures where liquid water is metastable. These correlations are designed to reproduce the best available data, which in most cases are described by formulations issued by the International Association for the Properties of Water and Steam (IAPWS). The equations presented here are simple enough to be used in applications such as spreadsheets. They provide a convenient alternative to the more complicated IAPWS formulations in cases where only liquid properties at near-atmospheric pressure are of interest without increasing the uncertainty beyond that of the more complex formulations.
Experimental density data are reported for four 1-C n -3-methylimidazolium-based ionic liquids (n ) 2, 4, 6), three with trifluoromethanesulfonate and one with a tetrafluoroborate anion, at atmospheric pressure and at temperatures in the range of (268 to 356) K. The buoyancy method was employed, using the microbalance of the Kru ¨ss K100MK2 tensiometer. At each nominal temperature 40 evaluated buoyancy and temperature readings in two runs were taken in most cases. Averages of density and temperature values obtained at the individual nominal temperatures are presented with an estimated total standard uncertainty less than 0.3 kg • m -3 (2.5 • 10 -4 F) and 0.02 K, respectively. The 83 new experimental data points on the density-temperature relation of the four ionic liquids of interest are means calculated from about 3000 individual density readings, which have been altogether taken in the present study. Measurements on two samples of the same stated high purity from different suppliers were performed for two ionic liquids, to demonstrate the influence of the sample origin.
Experimental airÀliquid interfacial tension data and density data are presented for two ionic liquids with the 1-C n -3methylimidazolium cation, n = 2 and 4, and the dicyanamide anion. The measurements were performed at atmospheric pressure in the temperature range from (278 to 356) K using the Kr€ uss K100MK2 tensiometer. The accuracy of the surface tension measurements was confirmed by employing the Wilhelmy plate and the du No€ uy ring methods in parallel. The combined expanded uncertainty at 0.95 confidence level associated with the Wilhelmy plate method is estimated to be 0.1 mN 3 m À1 . The density data were obtained using a buoyancy method with an estimated expanded uncertainty at 0.95 confidence level of 3 3 10 À4 F. An analysis of the experimental density data, using a group contribution model, performed for eight ionic liquids with the 1-C n -3-methylimidazolium cation (n = 2, 4, 6) and tetrafluoroborate and trifluoromethanesulfonate and the dicyanamide anion indicates that the uncertainty arising from impurities present in the sample is dominant. The upper-bound estimate for the overall expanded uncertainty (k = 2) in the density measurements including the uncertainty stemming from impurities in the sample is equal to ( 0.002F. The model is capable of providing predictions for pure imidazolium-based ionic liquids with [BF 4 ], [CF 3 SO 3 ], and [N(CN) 2 ] anions.
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