coefficiente di diffusione
The "Diffusion Coefficient" is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species (or the driving force for diffusion). Diffusivity is encountered in Fick's law and numerous other equations of physical chemistry.
Applicable units are those of quantitykind:DiffusionCoefficient
http://en.wikipedia.org/wiki/Mass_diffusivity
https://cdd.iec.ch/cdd/iec61987/iec61987.nsf/ListsOfUnitsAllVersions/0112-2---62720%23UAD031
The "Diffusion Coefficient" is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species (or the driving force for diffusion). Diffusivity is encountered in Fick's law and numerous other equations of physical chemistry.
$C_B \left \langle \nu_B \right \rangle = -D grad C_B$, where $C_B$ the local molecular concentration of substance $B$ in the mixture and $\left \langle \nu_B \right \rangle$ is the local average velocity of the molecules of $B$.
http://www.iso.org/iso/catalogue_detail?csnumber=31894