Thermodynamics of supercritical steam + carbon dioxide mixtures

Measurements of the excess enthalphy of steam + carbon dioxide have been made at temperatures from 363 to 698 K at pressures up to 6 MPa. Analysis of the measurements at low pressures yields values of the cross term second virial coefficient B₁₂. Evidence for a specific interaction between water and carbon dioxide is found, the enthalpy of association is ΔH = − 14 ±2 kJ mol⁻¹. The measurements at high pressures are fitted by the Peng-Robinson equation of state using values of the interaction parameter k_ij which are temperature dependent.