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

The PVT relationships of toluene were measured in the near-critical and sup ercritical regions. Measurements were made using a constant-volume piezomet er immersed in a precision thermostat. The volume of the piezometer V-PT wa s corrected for both temperature and pressure expansions. The temperature w as measured with a 10 Omega platinum resistance thermometer (PRT-10) with a n uncertainty of 10 mK. Pressure was measured by means of a dead-weight gau ge with an uncertainty of (0.0015 to 0.002) MPa. Uncertainties of the densi ty measurements are estimated to be (0.05 to 0.10)%, depending on the exper imental pressure and temperature. The volume of the piezometer V-PT was cal ibrated using a reference fluid (water) with well-known PVT properties at v arious temperatures and pressures. Measurements were made along various nea r-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 v alues 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.