THEORY OF DIFFUSION IN BINARY LIQUIDS
Section 17.4; Bird, Stewart and Lightfoot
This section involves a derivation of expressions for the liquid
diffusivities, specifically the empirical Wilkes-Chang
equation. Sample calculations are also shown using a programmed
function in MATLAB.
The cartoon below is a humorous presentation of the general concept of
diffusion. Bird, Stewart, & Lightfoot define diffusion as the
"movement of a chemical species from a region of high concentration to
a region of low concentration."
The graphic below exemplifies liquid diffusion in a simple system.
Here, a colored liquid solute is placed in the bottom of the container
(left) and solvent is poured over it. Over time, the solute spreads
throughout the solvent coloring the container with a bluish tint
(right).