Defined by
where
is the amount of species
flowing through unit area in unit time and
is the
concentration gradient of species
. Different
diffusion coefficients may be defined depending on the choice of the frame of reference used
for
and
. For systems with more than two components, the flow of any component and hence its
diffusion coefficient depends on the concentration distribution of all components. The limiting differential
diffusion coefficient is the value of
extrapolated to zero concentration of the diffusing species:
Source:
PAC, 1972, 31, 577
(Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix
II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry)
on page 617
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.
![[ D i ] = lim c i → 0 D i](../../mathml/D01704-8.png){kind=small}
