Talk:Potassium ferricyanide

From Wikipedia, the free encyclopedia

	Chemistry Portal Potassium ferricyanide is within the scope of WikiProject Chemicals, which aims to improve Wikipedia's coverage of chemicals. To participate, help improve this article or visit the project page for details on the project.
	This article is also supported by WikiProject Chemistry.
Start	This article has been rated as Start-Class on the quality scale.
Mid	This article has been rated as Mid-importance on the importance scale.
Article Grading: The following comments were left by the quality and importance raters: (edit · refresh) Only basic content at present, and applications. Needs chemistry and refs.

[edit] Prussian blue

it was stated that it is the presence of iron (III) ions (Fe3+) that cause potassium hexacyanoferrate to form a blue complex. It is in fact iron (II) ions (Fe2+). This is a very important difference and quite a major error to make. I have corrected the article as such.

No you are incorrect. I think you need to be clear as to the difference between ferrous ferrate and ferric compounds. I have corrected the article from your blunder.

I think you are both inaccurate. Potassium hexacyanoferrate(II), AKA potassium ferrocyanide or yellow prussate, reacts with ferric iron to form ferric ferrocyanide, or Prussian blue. Potassium hexacyanoferrate(III), AKA potassium ferricyanide or red prussate, reacts with ferrous iron to form ferrous ferricyanide, or Turnbull blue. Aristaea 17:32, 13 June 2007 (UTC)

I think Aristea is correct, see Prussian blue, a better article than this one! Walkerma 16:32, 2 August 2007 (UTC)

The consensus (see Dunbar review cited in Prussian blue) is that Turnbull's Blue and Prussian Blue are the same. They differ only in terms of the reagents - the details of the mixing gives rise to differing particle sizes hence slightly differing colors. In other words, the same compound can be made by adding Fe(II) salts to [[Fe(CN)₆]^3- or, complementarily and more typically, by treating Fe(III) salts with [Fe(CN)₆]^4-:

a precipitation process:

4 [Fe(H₂O)₆]³⁺ + 3 [Fe(CN)₆]^4- → Fe₇(CN)₁₈ = (Fe³⁺)4([Fe(CN)₆]^4-)3

redox followed by precipitation:

4 [Fe(H₂O)₆]²⁺ + 4 [Fe(CN)₆]^3- → [Fe(CN)₆]^4- + Fe₇(CN)₁₈ = (Fe³⁺)4([Fe(CN)₆]^4-)3

At least I think this is the way it is. BTW, I noticed that we lack a page on "nonstoichiometric compound," which describes Prussian Blue.--Smokefoot 17:18, 2 August 2007 (UTC)

Of course, you're right Smokefoot - I was giving a very quick answer before running to lab. I was recalling books I read in my youth - some time ago - which differentiated the two in the way Aristaea described. I had heard of the "new" knowledge, but it slipped my mind. As Prussian blue makes clear, they are chemically the same, although they may well be called different things based on the method of preparation, which can make all the difference! (as with Purple of Cassius). Sorry for my mistake. Walkerma 01:41, 3 August 2007 (UTC)

[edit] density of negative what?

"It is also used with sodium thiosulfate (hypo) to reduce the density of negative where the mixture is known as Farmer's reducer."

Density of Negative what? I think this is incomplete and should be completed for when people like myself come on here to get information about a specfic property of the compound.

Alexzander

It's a photographic negative - I've reworded it, because it was very unclear. Walkerma 16:26, 2 August 2007 (UTC)