Measurement of relative diffusion coefficients and thermal diffusion factors of CO 2 isotopes in Ar and He

Abstract

The ratio of the diffusion coefficients of the two CO 2 isotopes with mass 44 and mass 46 against the noble gases Ar and He have been measured within 1 part in 10 4, using the change in concentration ratio of these CO 2 isotopes that occurs when natural carbon dioxide diffuses through an other gas (“Rayleigh diffusion”). The experiments have been performed at the temperatures 22 and 70°C. A comparison between the results and the Chapman-Enskog theory, especially with regard to the relation between the separately experimentally determined thermal diffusion factor and the temperature derivative of the diffusion coefficient is made.