Diffusion in three‐component gas mixtures

Abstract A solution to the Stefan‐Maxwell diffusion equations for equimolal countercurrent diffusion in a three‐component gas mixture is obtained which is similar in form to Gilliland's equation for diffusion of two gases through a third inert gas. The important features of both types of diffusion are investigated and the conditions under which the following phenomena occur are determined: (1) diffusion barrier (the rate of diffusion of a component is zero even though its concentration gradient is not zero); (2) osmotic diffusion (the rate of diffusion of a component is not zero even though its concentration gradient is zero); (3) reverse diffusion (a component diffuses against the gradient of its concentration). A generalized driving force which describes these phenomena is introduced, and approximate equations are developed which give the individual rates of diffusion directly.