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Updated: Mar 22, 2026

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems
Published on: January 24, 2014
Concentration dependent refractive index of CO2/CH4 mixture in gaseous and supercritical phase
C Giraudet1, L Marlin2, D Bégué3
1Laboratoire des Fluides Complexes et leurs Réservoirs - UMR 5150, CNRS, Université de Pau et des Pays de l'Adour, 64600 Anglet, France.
Abstract:
Carbon dioxide (CO2)/methane (CH4) binary mixtures are investigated at pressure values up to 20 MPa at 303 K in order to investigate the pressure dependence of the optical concentration contrast factor, ∂n/∂c(P,T), through gaseous and supercritical phase. Refractive index is measured by means of a Michelson interferometer. Refractivities of the mixtures are found in good agreement with Lorentz-Lorenz predictions after density calculations by means of the AGA8-DC92 equation of state. Experimental polarizabilities of pure fluids are compared to quantum calculations of monomers and dimers for each pressure; it results that the quantity of dimers is small in the investigated thermodynamic conditions. Finally, by extending our experimental database with numerical simulations, we evidence that ∂n/∂cP,T presents a critical enhancement similar to heat capacity.
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