Measurement of the viscosity and density of a reference fluid, with nominal viscosity at T = 298 K and p = 0.1 MPa of 29 MPa·s, at temperatures between (273 and 423) K and pressures below 275 MPa

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 temperatur...