Coefficient of mutual diffusion
From AMS Glossary
coefficient of mutual diffusion
A quantity in the kinetic theory of gases that measures the tendency of gases to diffuse into one another in nonturbulent flow.
This diffusion coefficient is a property of the gases in question and of the assumed nature of the molecular impacts in the diffusion process.
Lettau, H. 1951. Compendium of Meteorology. 320–334.