Measurement and correlation of the (pressure, density, temperature) relation of argon I. The homogeneous gas and liquid regions in the temperature range from 90 K to 340 K at pressures up to 12 MPa

Comprehensive (p, ρ, T) measurements on pure argon have been carried out in the single-phase region (638 values) and along the entire coexistence curve (98 values). The results reported in this first paper cover the homogeneous gas and liquid region in the temperature range from 90 K to 340 K at pressures up to 12 MPa. The total uncertainty of the measurements is <(31.5·10-4ρ3 to 32.0·10-4·ρ3) with the exception of the temperature range from 150.7 K to 170K (Tc = 150.687 K) at densities between 200 kg·m-3 and 700 kg·m-3. There, the total uncertainty in pressure is <(31.0 10-4·p3 to 32·10-4p3). A virial equation of state has been established to describe the investigated homogeneous gas region for densities up to 0.3ρc (ρc = 535.6 kg·m-3) with an uncertainty of <31.5·10-4ρ3. From this equation numerical values for the second and third virial coefficients have been calculated. The experimental results have been compared with the results of previous workers.