Sound Dispersion in Substituted Methane—Inert Gas Mixtures

Abstract

Binary halomethane—noble gas mixtures were examined ultrasonically. The methanes used were CF₄, CHF₃, and CCl₂F₂ and the noble gases were Ar, Ne, and He. Results obtained show that the reciprocal relaxation times for these mixtures vary linearly with the concentration. Also, Ar—X collisions are less effective, He—X collisions are much more effective, and Ne—X collisions differ little from X—X collisions in vibrational energy transfer. X represents the dispersive gas. Theoretical values of Z₁₀^AB, the mean collision lifetime of an A molecule in an otherwise pure gas of B molecules, were calculated according to the Schwartz, Slawsky, and Herzfeld theory. Intermolecular potentials appropriate for the treatment of the data were examined, and it was found that the Lennard‐Jones 6:12 potential was appropriate for the noble gases, and the 7:28 form was appropriate for the halomethanes.