Vibrational Relaxation in Carbon Dioxide/Water-Vapor Mixtures

Sound-absorption and -velocity measurements in carbon dioxide water-vapor mixtures have been made over the temperature range 23°–195°C. The measurements were made using plane progressive waves inside glass tube 1.73 cm in diameter. Values of the mixture relaxation time τ (AB) obtained from the data increase from 0.27× 10−8 sec at 23°C to 0.58× 10−8 sec at 195°C, displaying no minimum value as has been reported previously by other authors. The collision efficiency decreases slightly over this temperature range. Values of an average collision diameter calculated from the experimental data are in good agreement with values predicted by the Widom-Bauer theory, the basis of which is a chemical affinity between the CO2 and H2O molecules.