Talk:Ellingham diagram

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Chemistry (Rated Start-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Chemistry, a collaborative effort to improve the coverage of chemistry on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Start-Class article Start  This article has been rated as Start-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.

Delta-G constant?[edit]

WHY ΔG'remanins ΔG'. even when temperature is changing —Preceding unsigned comment added by (talk) 05:46, 15 August 2007 (UTC)


referring to the diagram at [1], the following article text is confusing: "but the ΔG of the oxidation always becomes more negative with higher temperature, and thus the reaction becomes more probable statistically. At a sufficiently high temperature, the sign of ΔG may invert (becoming negative) and the oxide can spontaneously reduce to the metal." -- (talk) 14:38, 26 December 2009 (UTC)

Who was Ellingham? Ellingham approximation?[edit]

Does anyone know something about Ellingham and when he/she introduced this diagram? Ideally we should give the original reference.

Also, the French Wikipedia has two relevant articles: one on the Ellingham diagram which is a shortened version of this one, and a second on the "Ellingham approximation" which is said to be that ΔH(T) and ΔS(T) are approximately constant over a wide range of T. This English article does make the equivalent statement that all Ellingham diagrams are basically straight lines, but is this really known as the Ellingham approximation? If someone has a source, it would be interesting to insert the fact in this article (though I think a second article is not necessary). Dirac66 (talk) 01:18, 16 October 2010 (UTC)

I've taught this material in a French university, and we do point out that the constancy of ΔH and ΔS with temperature (apart from at phase changes) is only an approximation. On the other hand, it's a pretty good one, and I don't think it is original to Ellingham. You can construct an Ellingham diagram without that approximation, but it's far more trouble than it's worth! I've never heard the term "Ellingham approximation", either in France or elsewhere.
I've collected together the information I could find about Harold Ellingham in a short stub article. Physchim62 (talk) 15:24, 31 December 2010 (UTC)
Good work on the biographical research - thank you. And I agree with your comments about the constancy of ΔH and ΔS. I'll put a note at fr:Discussion:Approximation d'Ellingham asking for a source for the term. Dirac66 (talk) 20:01, 31 December 2010 (UTC)

Diagram added[edit]

In response to the diagram request posted today, I have inserted a diagram from Commons which I found in the French article. I used (some of) the English caption in the Commons description, but there are still a few French words on the actual diagram which hopefully are simple enough for everyone.

There are also some more elaborate diagrams in the external links, but usually these cannot actually be copied into the article because of copyright problems. Dirac66 (talk) 17:36, 28 October 2010 (UTC)

Thanks! DMacks (talk) 18:51, 28 October 2010 (UTC)

It is commonly known that iron/chrome carbides are stable at lower temperatures in the presence of carbon monoxide than are the metals. The statement that chrome carbides are stable at high temperatures and that carbon can therefore not be used to form chrome metal, must be wrong. Could someone please prove me wrong or explain the fact that chrome ore is commonly reduced with carbon. In an article "Solid state reduction of chromite with CO", authors Xiao, Schuffeneger, Reuter, Holappa and Seppala, a photomicrograph is shown with chrome metal and no carbides in the immediate vicinity. — Preceding unsigned comment added by (talk) 16:12, 28 March 2013 (UTC)