Navigation Links
Fick's law of diffusion


Fick's laws of diffusion describe diffusion.

Contents

History

Fick's laws of diffusion were derived by Adolf Fick in the year 1858.

Fick's First Law

Fick's First Law is used in steady state diffusion, i.e., when the concentration within the diffusion volume does not change with respect to time (Jin=Jout).

Where

  • J is the diffusion flux in dimensions of [parts length-2 time-1]
  • D is the diffusion coefficient in dimensions of [length2 time-1]
  • c is the concentration in dimensions of [parts length-3]
  • x is the position

Fick's Second Law

Fick's Second Law is used in non-steady state diffusion, i.e., when the concentration within the diffusion volume changes with respect to time.

Where

  • c is the concentration in dimensions of [parts length-3]
  • t is time
  • D is the diffusion coefficient in dimensions of [length2 time-1]
  • x is the position

A Biological Perspective

The first law gives rise to the formula

It states that the rate of diffusion of a gas across a membrane is

  • Constant for a given gas at a given temperature by an experimentally determined factor, K
  • Proportional to the surface area over which diffusion is taking place, A
  • Proportional to the difference in partial pressures of the gas across the membrane, P2 - P1
  • Inversely proportional to the distance over which diffusion must take place, or in other words the thickness of the membrane, D.

Fick's first law is also important in radiation transfer equations. However, in this context it becomes inaccurate when the diffusion constant is low and the radiation becomes limited by the speed of light rather than by the 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 by using this law together with Graham's law.

See also

References

  • W.F. Smith, Foundations of Materials Science and Engieering 3rd ed., McGraw-Hill (2004)

'"/>


(Date:4/11/2017)... 2017 Research and Markets has announced the ... to their offering. ... eye tracking market to grow at a CAGR of 30.37% during ... Market 2017-2021, has been prepared based on an in-depth market analysis ... and its growth prospects over the coming years. The report also ...
(Date:4/6/2017)... , April 6, 2017 Forecasts ... ANPR, Document Readers, by End-Use (Transportation & Logistics, Government ... Oil, Gas & Fossil Generation Facility, Nuclear Power), Industrial, ... Other) Are you looking for a definitive ... ...
(Date:4/5/2017)... KEY FINDINGS The global market for stem ... 25.76% during the forecast period of 2017-2025. The rise ... growth of the stem cell market. Download ... The global stem cell market is segmented on the ... cell market of the product is segmented into adult ...
Breaking Biology News(10 mins):
Other biology definition