User:Brian P. Josey/Notebook/2010/07/12

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Wrapping Up Notes

Today will be the last day that I'll be posting notes on diffusion and everything else in my notebook.

The diffusion of solutes over a surface can be modeled mathematically as:

js = − PsΔc

where

• js is the flux of solutes over the surface,
• Ps is the permeability of the membrane to the solute, and
• Δc is the change from the higher concentration to the lower concentration

For a spherical surface, the relaxation of a concentration jump, is:

$- \frac {d(\Delta c)} {dt} = \frac {AP_s} {V} \Delta c$

with A being the area of the sphere, and V its volume.

Nernst Equation

There is a very interesting discussion of ions diffusion in solution while under the influence of a potential gradient. This is useful to understand because it is similar to what I am doing. For example, with simple common salt, when it dissolves in solution, it separates out into positively and negatively ions that can move depending on how the potential difference is set up.