Diffusionsmittel

Diffusionsmittel (diffusion medium) is a term used in German to describe any substance or phase that permits the diffusion of another substance. In diffusion processes, the diffusing species moves through the medium by random molecular motion, and the rate and extent of diffusion are governed primarily by Fick's laws, as well as by temperature, viscosity, and the size of the diffusing molecules.

Common examples of diffusion media include gases such as air, liquids such as water or organic solvents, gels such as agarose or polyacrylamide, and porous solids such as silica or polymer membranes. The choice of medium influences diffusion coefficients, which quantify how fast a substance spreads through the medium. In porous or heterogeneous media, factors such as tortuosity and porosity further modify diffusion behavior.

Applications range from basic teaching experiments, where dyes diffuse in agar plates to illustrate diffusion, to research in chemistry and biology for measuring diffusion coefficients. In materials science and engineering, diffusion media are important for processes such as membrane separation, battery and fuel-cell operation, and controlled release in pharmaceutics.

Measurement and analysis often involve diffusion cells or other experimental setups, and rely on models based on Fick's laws. Temperature control, concentration gradients, solvent properties, and molecular size are key parameters. Safety and handling depend on the specific medium used.