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Diffusion

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Encyclopedia of Geochemistry

Part of the book series: Encyclopedia of Earth Sciences Series ((EESS))

Definition

Diffusion arises from random motions of particles in a fluid or solid. Here the particles can be neutral molecules or atoms, or charged cations or anions. The particle that diffuses through a medium or substance is called diffusant. Diffusion is a microscopic kinetic phenomenon that results in intermingling and homogenization of the chemical components in a substance. It is part of the mixing process that is not accounted for by the bulk flow or advection of the chemical system. The word “diffusion” originates from the Latin word “diffundere” which means to pour out or spread out.

Fick’s Laws of Diffusion

The spreading of diffusant in a medium can be quantified by applying the laws of diffusion which are established through observations of natural phenomenon and laboratory diffusion experiments. During diffusion, random motions of the particles in a chemically heterogeneous phase will redistribute its constituent from regions of high concentration to low concentration, which...

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Liang, Y. (2018). Diffusion. In: White, W.M. (eds) Encyclopedia of Geochemistry. Encyclopedia of Earth Sciences Series. Springer, Cham. https://doi.org/10.1007/978-3-319-39312-4_336

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