BINARY DIFFUSION IN COMPRESSED ARGON-METHANE MIXTURES

The rate of diffusion of CH4 through Ar has been measured at room temperature and at pressures from 20 to 150 atm. The diffusion takes place in a long narrow channel and is monitored by continuous measurements of the intensity of the 3.3μ absorption band of CH4. Each concentration vs. time curve for a diffusion run at a given pressure and temperature provides a series of in principle constant values for the binary diffusion coefficient D12. Deviations of constancy are observed and their probable cause is discussed. The product of D12 and the gas density, independent of pressure in elementary kinetic theory, should decrease by about 15% according to Enskog's theory; in reality the value of this product decreases by as much as 40% at the highest pressures. © 1969.