Diffusion

Name:
Diffusion
Detailed information:
The spontaneous mixing of one substance with another when in contact or separated by a permeable membrane or microporous barrier. The rate of diffusion is proportional to the concentration of the substances and increases with temperature. Diffusion occurs most readily in gases, less so in liquids, and least in solids. The theoretical principles are stated in Fick's laws. In gases, diffusion takes place counter to gravity, and the rate at which different gases diffuse into a particular gas (e.g., air) is inversely proportional to the square root of the density. For example, carbon dioxide and chlorine vapor will diffuse in air until a uniform mixture results. Diffusion occurs in the cell walls of plants and animals (osmosis). Many substances diffuse through a parchment membrane.See Dialysis; Diffusion, Gaseous; Osmosis.