Talk:Mass diffusivity

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Mathematically Ambiguous Definition[edit]

I've never needed to look much into diffusion coefficients before, so I was confused when my "first impression" of the definition lead to the inverse of the correct units! The definition as stated would allow either grad(concentration)=D*Flux or D*grad(concentration)=Flux. Clicking on the link to Fick's Law clears this up, but perhaps it would be more appropriate to say that the diffusion coefficient is --defined-- by Fick's Law (and then give the eqn), rather than saying that it is "encountered in Fick's Law". I'll leave this edit to someone else, since this is a new topic for me.

Cheers, Catfisherguy 18:50, 18 July 2011 (UTC) — Preceding unsigned comment added by Catfisherguy (talkcontribs)

Requested move[edit]

The following is a closed discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was Move Parsecboy (talk) 00:44, 19 February 2009 (UTC)

This is NOT a biology article... please someone remove the tag --203.199.213.66 (talk) 08:59, 9 May 2008 (UTC)

Units are not necessarily right either, it's mass per time per area per driving force, so they units can vary greatly. —Preceding unsigned comment added by 64.113.87.104 (talk) 00:12, 18 September 2008 (UTC)

I agree that this article is not specific to biology at all. I am considering renaming it to Diffusivity of mass or perhaps to Molecular diffusivity of mass (so as not to mix it with eddy diffusivity of mass). After this, we could merge into it some of the relevant content found in article Fick's law of diffusion. Other suggestions welcome. Stan J. Klimas (talk) 00:46, 8 January 2009 (UTC)
I second the suggestion to move this to a new name. Biology is in no way the overarching area for this. I favor Mass Diffusivity, as this is the most common usage in my experience. It balances nicely with things like Thermal Diffusivity. Eddy diffusivity can stand on its own and be handled through disambiguation. The Fick's law of diffusion also needs some work, and I agree that some of that content should be moved here. Why don't we get started by saying here that we'll give this a few weeks for others to pipe in, and then take action in Mid January 2009 if there is no countering consensus. --Lacomj (talk) 02:08, 8 January 2009 (UTC)
Sounds good to me: move to "Mass diffusivity". By the way, the article Molecular diffusion also needs work. It seem that the topic of diffusion has not been very well covered in en.wikipedia so far. One could probably re-use some material from de.wikipedia. Stan J. Klimas (talk) 02:26, 8 January 2009 (UTC)
I noticed that the page was already moved once. Also, the target page is taken by a re-direct to this article. However, in my opinion, it does not change anything. The move is still the right thing to do, in my opinion. Stan J. Klimas (talk) 23:31, 11 February 2009 (UTC)
The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Unit incorrect?[edit]

Concerning the comment in the archive discussion above:

Units are not necessarily right either, it's mass per time per area per driving force, so they units can vary greatly. —Preceding unsigned comment added by 64.113.87.104 (talk) 00:12, 18 September 2008 (UTC)

It seems to me that the unit is correct, even when the diffusion process is described with chemical potential as the driving force (see Fick's law of diffusion for the definition of the symbols)

J_i = - \frac{D c_i}{RT} \frac{\partial \mu_i}{\partial x}

Not sure if there is any other possibility for units. Stan J. Klimas (talk) 09:22, 11 March 2009 (UTC)

Agreed. Scientific29 (talk) 13:50, 3 June 2014 (UTC)

Units[edit]

No units are called out for D for the gasses formula.

192.249.47.196 (talk) 22:25, 17 November 2009 (UTC)

Fixed. Scientific29 (talk) 13:47, 3 June 2014 (UTC)

Article title[edit]

"Mass diffusivity" is in my opinion a nonsense term. Mass cannot diffuse, because it is not a substance. Mass is a property of elementary particles (just like charge, spin, isospin, etc.). Particles diffuse in response to gradients in their chemical potentials (and carry their mass and other properties) with them. I therefore suggest the article be renamed "Particle Diffusion." Also, this article is written purely from a chemist's perspective. Semiconductor and solid state scientists concern themselves with diffusion of electrons and holes inside a crystal, which has nothing to do with molecules. A broader perspective would be useful. — Preceding unsigned comment added by Enginerd201 (talkcontribs) 19:22, 15 June 2011 (UTC)

Equation indices[edit]

I think that the indices 1,2 are incorrect in the equation following this sentence. Can someone please check? Thank you! 131.215.220.161 (talk) 18:45, 2 May 2014 (UTC)

"An approximate dependence of the diffusion coefficient on temperature in liquids can often be found using Stokes–Einstein equation, which predicts that:"

The indices on some of the variables were not properly subscripted, if that is what you mean. Otherwise, the equation appears correct at this time. Scientific29 (talk) 13:49, 3 June 2014 (UTC)