Ultrasonic Absorption in Mixtures of Methane with H₂, D₂ and He

In this paper an apparatus is described for making adsorption measurements on the basis of a pulse technique in the range of 50 kHz/atm to 3 MHz/atm. Two Sell-transducers are employed and the sound intensity at the receiving transducer is measured as a function of the path length to give the absorption coefficient. In the mixtures CH₄-H₂, CH₄-D₂ and CH₄-He the relaxation time is determined for several high methane concentrations. The relaxation times for vibrational deactivation of CH₄ dilute in M (M = H₂, D₂, He) were found by extrapolation. Within the experimental error of such measurements there is agreement with the results of other investigators. There is no indication of a non-linear behaviour of the reciprocal relaxation time as a function of the mole fraction.