## differential diffusion coefficient

Also contains definition of: limiting differential diffusion coefficient
https://doi.org/10.1351/goldbook.D01704
Defined by $D_{i} = \frac{-J_{i}}{\nabla c_{i}}$ where $$J_{i}$$ is the amount of species $$i$$ flowing through unit area in unit time and $$\nabla c_{i}$$ is the @C01227@ of species $$i$$. Different @D01716@ coefficients may be defined depending on the choice of the frame of reference used for $$J_{i}$$ and $$\nabla c_{i}$$. For systems with more than two components, the flow of any component and hence its @D01719@ depends on the concentration distribution of all components. The limiting differential diffusion coefficient is the value of $$D_{i}$$ extrapolated to zero concentration of the diffusing species: $[D_{i}]=\lim _{c_{i}\rightarrow 0}D_{i}$
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 [Terms] [Paper]