Talk:Chromic acid

Topic of Article

Maybe this article should be about Chromium trioxide with with a section on chromic and dichromic acids as side issues. Chromium trioxide is a stable and isolable compound, even though it is reactive with many other compounds. Chromic and dichromic acids do not seem to be isolable, however. Also, I would expect in an acidic solution the chromic/dichromic equilibrium to be pushed practically all the way to dichromic acid. H Padleckas 14:28, 2 May 2005 (UTC)

I don't mind too much, but I see your point that if we want to list properties in a table, it needs to be chromium trioxide or chromium(VI) oxide. We could make chromic acid a redirect to that, with a full coverage of chromic acid oxidations on this page. Good idea Walkerma 19:36, 23 May 2005 (UTC)

Chromia

I thought I'd drop a note here too that I requested in Talk:Chromia that the relations between several similar terms (that are also related to this article) be clarified. Chromia is about chromium(III) oxide, and Chromium trioxide currently redirects to Chromic acid (see also discussion above). Rl 16:41, 21 August 2005 (UTC)

Ethanol in contact with chromium trioxide will ignite

This is complete rubbish and should be removed from the article. Just in case, I dropped some CrO3 into ethanol ten minutes ago. No reaction.

If you carry on in this manner, Darwinian evolution will come into work to enhance the competence of future chemists. Physchim62 (talk) 13:39, 19 July 2006 (UTC)

Chromates

As suggested by their name, chromates tend to have very bright, bold coloration. If anyone has a photograph of any of the compounds described in this page, it would certainly make the article more readable and more interesting.

We have ammonium dichromate and potassium dichromate as images. Physchim62 (talk) 08:52, 3 November 2006 (UTC)

Cleaning

"Moreover, there are other cleaning methods that are just as effective, safer, and more environmentally friendly." Perhaps examples would be helpful/informative? Thelbert 16:19, 20 November 2006 (UTC)

I am also interested in knowing cleaning methods that are as effective as chromic acid. Off the top of my head I don't know any. Delmlsfan 03:23, 3 January 2007 (UTC)

Depends what you're trying to clean, but an alcoholic solution of potassium hydroxide (10–15%) is one that I use quite frequently. Glassware comes out of the solution very slippery, so it is best to have a bath of 5% hydrochloric acid handy to do the neutralising before rinsing. Physchim62 (talk) 08:31, 5 January 2007 (UTC)

Chromic acid formula mismatch

I just noticed that in this page the formula for chromic acid is H2CrO4 but in List of inorganic compounds page it is listed as "Chromic acid – CrO3".

It seems inconsistent. Welcome to inorganic chemistry! The usage is indeed sloppy and we should fix this. A series of compounds probably form when CrO₃ is added to water or when H⁺ is added to a solution of CrO₄^2- or Cr₂O₇^2-. Names for such solutions were coined years in advance of the corresponding characterization of their structural chemistry, which remains incomplete and complex because some of these species only exist as mixtures and only in solution. Titanic acid, molybdic acid, vanadic, etc. acids are even less well characterized. Having said all that, CrO₃ is not chromic acid in my book: it is the anhydride of chromic and polychromic acids. At least that is my perspective on this situation.--Smokefoot 03:59, 3 August 2007 (UTC)

That is correct IMO, but it is also true that CrO3 is commonly called chromic acid in industry (the first paragraph of the article already says that) and in old books. In the old times (19th century), chemists didn't differentiate between acids and anhydrides, and books gave formulas such as SO3 for sulfuric acid. While the no one calls SO3 sulfuric acid anymore (as far as I know), CrO3 is still sometimes called chromic acid. I've also heard organic chemists refer to CrO3 as chromic acid, although of course they mean the mixture of CrO3 + H2SO4 that is actually used (see Jones oxidation). --Itub 09:05, 3 August 2007 (UTC)

CrO3 dissolves in water to make a solution containing H+ and CrO4-- ions, which is a dilute solution of chromic acid. Interestingly, CrO3 shows acid properties without water being present e.g. CaO + CrO3 --> CaCrO4. It is an example of a "Lewis acid" which meets the (broader) definition of an acid suggested by the chemist G.N.Lewis in the 1920s. 2corner (talk) 11:46, 15 May 2009 (UTC)

Chromium(V)

When Chromium(VI) is reduced, it is usually to Chromium(III) not Chromium(V) which is very unstable.

I would like to see a reference to or evidence of Cr(V). 2corner (talk) 10:08, 25 November 2008 (UTC)

dichromic acid

I have not been able to find anything concrete about this species, but it has a CAS number 13530-68-2. I'll need to look at Gmelin or another specialist publication on chromium to get the citation needed. Petergans (talk) 15:13, 14 December 2010 (UTC)

Ball and stick model

The ball and stick model seems wrong to me. As far as I know, the coordination around Cr should be tetrahedral, and not square planar.--Albris (talk) 23:11, 16 December 2010 (UTC)

I agree, they are not drawn very well, but I always saw them as tetrahedral. It's not always easy to show the 3-D structure on a 2-D surface. Petergans (talk) 10:03, 17 December 2010 (UTC)

google description is corrupt

It looks like this:

SMILES. O[Cr](O)(=O)=O. O=[Cr](=O)(O)O. InChI. InChI=1S/Cr.2H2O.2O/h;2*1H2; ;/q+2;;;;/p-2 Yes Y Key: KRVSOGSZCMJSLX-UHFFFAOYSA-L Yes Y ...

StainlessSteelScorpion (talk) 17:29, 24 November 2013 (UTC)

Reprotection of magnesim and its alloys

one of the most important application of selenious acid is in re protection of magnesium and its alloys since 1960.

Please someone add this:

https://books.google.com/books?id=TO9dSoi0P6gC&pg=PA255&lpg=PA255&dq=selenious+acid+magnesium&source=bl&ots=DldP3lj4Ra&sig=VuJwWfr28e3OpyPuIY_Wq2EUenA&hl=en&sa=X&ved=0CCkQ6AEwAmoVChMIq-yOz4DjxwIVA70UCh1D3gI9#v=onepage&q=selenious%20acid%20magnesium&f=false

I am not familiar with the process.

Thank you in advance

update... oops... sorry.. it was for selenious acid!

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Confusing chromic acid, dichromic acid and chromium trioxide with each other

This article is ambiguous, because some data in this article actually refer not to chromic acid and dichromic acid, but to chromium trioxide, and those three compounds are not the same. For some data in this article, it is unclear which compound they refer to. I know, in old times and in old articles, even in some new articles across the Internet, chromium trioxide is incorrectly called chromic acid, but nowdays it is known those two species are two different compounds, thus, some data in this article are obsolete. And chromic acid and dichromic acid do not seem to be isolable, they exist only in a solution, where many species are found in equilibrium, including chromium trioxide. Chromium trioxide should not be called chromic acid on Wikipedia! Please someone clarify those ambiguities in this article. Bernardirfan (talk) 22:28, 9 January 2024 (UTC)

I will try to work on this article. The literature is thin and the opinions/fact ratio is high. I tend to remove content that I think is tangential or dubious, so feel free to object or reinstate. --Smokefoot (talk) 19:26, 10 January 2024 (UTC)

Thank you. Bernardirfan (talk) 23:02, 10 January 2024 (UTC)