Experimental setup to measure critical properties of pure and binary mixtures and their densities at different pressures and temperatures: Determination of the precision and uncertainty in the results

We describe an experimental setup to measure critical properties and density as a function of pressure and temperature. Critical temperature and critical pressure (Tc, Pc) are measured with a flow apparatus, and detected by critical opalescence. Precision in measuring critical points for pure compounds and binary mixtures are characterized in terms of repeatability and confidence interval. The volumetric properties are determined with a high-pressure vibrating-tube density meter, calibrated from 278.15 to 318.15 K at pressures up to 200 × 105 Pa. Density values are validated for pure compounds by determining the absolute and relative root-mean-square deviations to CO2 data obtained from the Span and Wagner equations of state (EOS), and for binary mixtures by determining the relative mean standard deviation of density, s¯ρr. Both the critical and volumetric experimental results have been compared with literature data and values obtained from the Peng–Robinson and Patel–Teja cubical equations of state.