THEORY OF DIFFUSION IN BINARY LIQUIDS
Section 17.4; Bird, Stewart and Lightfoot

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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).

• Derivation of Liquid Diffusivities (Shown here with a Maple Worksheet)
• Matlab Program, 'ldiff', for calculations (Shown here with in MATLAB code)