The viscosity and density of diisodecyl phthalate (DIDP), with a nominal viscosity at T = 298 K and p = 0.1 MPa of 87 mPa·s, has been measured at temperatures from (298.15 to 423.15) K and pressures from (0.1 to 70) MPa. A vibrating wire viscometer, with a wire diameter of about 0.15 mm, was used for the viscosity measurements at pressures up to 70 MPa, and the results have an expanded uncertainty (k = 2), including the error arising from the pressure measurement, of between ± (2 and 2.5) %. The density was obtained from two vibrating tube densimeters, one for operation at p ≈ 0.1 MPa with an expanded uncertainty (k = 2) of about ± 0.1 % and the other one that functioned at pressures up to 70 MPa, with an expanded uncertainty (k = 2) of about ± 0.3 %. Measurements of density and viscosity at p = 0.1 MPa were conducted with three samples of DIDP each with different purity stated by the supplier and as a function of water mass fraction in the range (20 to 417)·10-6. The values obtained agreed within the estimated expanded uncertainties of the measurements. One sample was from the same lot and purity as that used by both Caetano et al. (J. Chem. Eng. Data 2005, 50, 1875−1878) and Harris and Bair (J. Chem. Eng. Data 2007, 52, 272−278) for their measurements of viscosity and density. The measured viscosity and density are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with the expanded (k = 2) uncertainties. The viscosities at p = 0.1 MPa agree with values reported in the literature within the combined estimated expanded (k = 2) uncertainties of the measurements while our densities differ by no more than ± 0.15 %. At p > 0.1 MPa the only other literature values are those reported by Harris and Bair. Deviations of their values from our smoothing equation increase with increasing pressure to be < ± 2 % at p < 1 MPa and between (−9 to 11) % at p = 50 MPa; these differences are within 2.5 times the combined uncertainty.

A vibrating wire viscometer has been developed with an electrically insulating tensioning mechanism. It has been used with two wires, one of diameter 0.05 mm the other of diameter 0.15 mm, to measure the viscosity of methylbenzene and two reference fluids with viscosities of (14 and 240) mPa·s at T = 298 K and p = 0.1 MPa at temperatures in the range from (298 to 373) K and pressures below 40 MPa, where the viscosity covers the range from (0.3 to 100) mPa·s with an uncertainty of < 0.6 %. The results so obtained differ from literature values by < 1 %. Measurements with the 0.150 mm diameter wire at T = 301 K demonstrate that the upper operating viscosity is 200 mPa·s with an uncertainty of about 3 %.

The viscosity, density, and electrical conductivity of 1-hexyl-3-methylimidazolium bis(trifluorosulfonyl)imide have been measured at temperatures from (288 to 433) K and at pressures up to 50 MPa. A vibrating wire viscometer was used for the measurements of viscosity that have an expanded uncertainty (k ) 2) of ( 2 %. The density was obtained from a vibrating tube densimeter with an expanded uncertainty (k ) 2) of ( 0.3 %. The electrical conductivity κ(f f∞) was determined from impedance measurements at frequencies in the range (0.5 to 10) kHz with an expanded (k ) 2) uncertainty of ( 2 %. All measurements were conducted with a sample distributed by NIST as part of an IUPAC project. The water mass fraction was determined before and after the measurements. The viscosity and density of a sample with initial water content of 7‚10 -6 were represented by interpolating expressions with standard deviations of 0.4 % and 0.03 %, respectively. Differences between the experimental and calculated values are comparable with the expanded (k ) 2) uncertainties. For temperatures that overlap the temperature range (288 to 433) K at p ) 0.1 MPa, literature values of density differ by e ( 0.2 % while the reported viscosities differ by e ( 7 % from these empirical representations of the measurements. There are no values of the viscosity at p > 0.1 MPa reported in the literature to compare our results. At p > 0.1 MPa, the literature values for density reported by Gomes de Azevedo (J. Chem. Thermodyn. 2005, 37, 888-899) deviate from our smoothing equation by less than -0.2 % at temperatures and pressure that overlap ours. The electrical conductivity was determined on a sample with initial water mass fraction of 90‚10 -6 . The results were represented within the expanded uncertainty by an empirical function against which the literature values differed by no more than ( 5 %.

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We have measured the viscosity and density of certified reference material S20, with a nominal viscosity at T ) 298 K and p ) 0.1 MPa of 29 mPa‚s, at temperatures in the range of (273 to 423) K and pressures between (0.1 and 275) MPa. A vibrating wire viscometer, with a wire diameter of about 0.15 mm, was used for the viscosity measurements at pressures up to 70 MPa, and the results have an expanded uncertainty (k ) 2) of ( 2 %, while a falling sinker viscometer was used for measurements at pressures up to 275 MPa with an expanded uncertainty (k ) 2) of ( 2.3 %. The density was obtained from vibrating tube densimeters with an uncertainty (k ) 2) of about ( 0.2 %. The measured viscosity and density are represented by interpolation expressions. Our equation represents the measured viscosities to within ( 2.3 % and the densities to within (0.2 %. These differences are comparable with the expanded uncertainty (k ) 2) of our measurements. The measurements extend the pressure range by 275 MPa and the temperature range by 50 K over which the viscosity and density of these fluids are provided by the supplier. These measurements complement those reported in the literature for S20, at pressures and temperatures exceeding the certified values, and extend the temperature range by 30 K and the upper pressure by 220 MPa. The viscosities reported here differ from values reported in the literature for batches different to that used here by less than ( 4.5 %, which is within the combined estimated expanded (k ) 2) uncertainties of the measurements and places a plausible bound on the certainty of η(T, p) for another batch of S20 that might be used as a calibrant for other instruments.