MEASUREMENTS OF THE (PRESSURE, DENSITY, TEMPERATURE) RELATION OF SULFUR-HEXAFLUORIDE (SF6) IN THE HOMOGENEOUS REGION AT TEMPERATURES FROM 321.15-K TO 333.15-K AND AT PRESSURES UP TO 8 MPA AND ON THE COEXISTENCE CURVE AT TEMPERATURES FROM 288.15-K TO 315.15-K

This paper presents accurate (p, ρ, T) measurements on pure sulphur hexafluoride (SF6) on four supercritical isotherms (321.15 K, 323.15 K, 328.15 K, and 333.15 K) at pressures from 0.5 MPa to 8 MPa. The measurements have been carried out to determine reference values for a new apparatus specially developed for (p, ρ, T) measurements in the immediate vicinity of the critical point. The total uncertainty of the measurements is <(|0.00015·ρ| to |0.00025·ρ|) for densities below 400 kg · m-3 and above 1000 kg · m-3. In the range from 400 kg · m-3 to 1000 kg · m-3 (critical density ρc = 742.0 kg · m-3) the total uncertainty was estimated to be |0.0001 · p| to |0.0002 · p|. The values for the second and third virial coefficients are also given, which have been determined from the (p, ρ, T) measurements at low densities. Furthermore, several measurements of the vapour pressure, the saturated-liquid density, and the saturated-vapour density in the temperature range from 288.15 K to 315.15 K have been carried out. The experimental results have been compared with the results of previous workers. © 1992 Academic Press Limited All rights reserved.