PVT measurements for toluene in the near-critical and supercritical regions

Abstract

The PVT relationships of toluene were measured in the near-critical and supercritical regions. Measurements were made using a constant-volume piezometer immersed in a precision thermostat. The volume of the piezometer VPT was corrected for both temperature and pressure expansions. The temperature was measured with a 10 Ω platinum resistance thermometer (PRT-10) with an uncertainty of 10 mK. Pressure was measured by means of a dead-weight gauge with an uncertainty of (0.0015 to 0.002) MPa. Uncertainties of the density measurements are estimated to be (0.05 to 0.10)%, depending on the experimental pressure and temperature. The volume of the piezometer VPT was calibrated using a reference fluid (water) with well-known PVT properties at various temperatures and pressures. Measurements were made along various near-critical and supercritical isotherms between (591 and 673) K at pressures from (4 to 36) MPa. The measured PVT data for toluene were compared with values calculated from equations of state and previous measurements of other authors. The accuracy of the method was confirmed by PVT measurements for pure water in the critical and supercritical regions.