Ficks law of diffusion

• proportional to the difference in partial pressure
• proportional to the area of the membrane
• inversely proportional to the thickness of the membrane

Fick's law is also important in radiation transfer equations. In this context it becomes inaccurate with the diffusion constant is low and the radiation becomes limited by the speed of light rather than by resistance of the material the radiation is flowing through. In this situation, one can use a flux limiter[?].

The exchange rate of a gas across a fluid membrane can be determined using this law together with Graham's law.

See also : lung -- alveoli