Talk:Manganese dioxide

Smell

What does it smell like? --Homfrog^{Tell me a story!} 00:22, 20 October 2006 (UTC) MnO2 is a rock, and most rocks dont have vapor pressures, so one cannot smell them.--Smokefoot 00:25, 20 October 2006 (UTC)

Needs review

Even diamond has a vapor pressure, steel too.

Anyway, the "other oxides" section is not relevant. If someone could put up some stuff on the synthesis of MnO2 it would be better than the stuff on KMnO4. It smells like damp chalk btw. And it stains you fingers brown! Spgoo1 03:18, 23 July 2007 (UTC)

Chemical manganese dioxide The formulas claimed are not balanced, neither in atom count nor in oxidation numbers. It could be oxygen that is missing. Reference 2 seems somewhat old. 150.227.15.253 (talk) 08:34, 30 July 2010 (UTC)

For as far as I can see, the formulas are balanced, I presume you are talking about the N2O4 reaction. I count one Mn, 2 N, and 6 O on both sides. Also, the age of a reference does not invalidate it (it might be follow up references that do, but which are missed here). Could you please explain a bit further? --Dirk Beetstra ^{T C} 08:39, 30 July 2010 (UTC)

Unclear English

This article is hard to read due to poor English usage. Quoting one particularly incomprehensible section: "Forms of MnO2 useful as an oxidizing reagent is not a straightforwardly stoichiometric reagent, far from it. The method of reagent preparation, sample history, and solvents are serious considerations." I'd clean it up, but I have no idea what information those sentences are attempting to convey. 97.82.247.200 18:36, 10 September 2007 (UTC)

Thanks for pointing out the strange English. The section should be more comprehensible now.--Smokefoot 00:14, 11 September 2007 (UTC)

Move the article to Manganese dioxide?

The following discussion is an archived 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, I suppose. Duja► 14:40, 24 September 2007 (UTC)

---

We had a related discussion on Talk:Osmium tetroxide, where it was decided to move the article from "osmium(VIII) oxide" to osmium tetroxide. I recommend that we move this article to what people call this stuff, the dioxide. TiO₂ is named Titanium dioxide. Not sure that I have the administrative authority/power to make such a move. Please register your concerns if you have any on this move.--Smokefoot 00:20, 11 September 2007 (UTC)

I don't see why. Manganese(IV) oxide is less ambiguous and more accurate, apart from being IUPAC recommended. What would be accomplished by moving it? Loom91 13:44, 17 September 2007 (UTC)

We moved Osmium(VIII) oxide to what everyone calls that stuff - Osmium tetraoxide. Otherwise these articles are hostage to orthodoxy vs the more common terminology. And the term manganese (IV) oxide is in a sense ambiguous because the stoichiometry is not explicit. Professional journals and monographs refer to this material as manganese dioxide, not manganese(IV) oxide. For an analogous case, please see the discussion at Talk:Osmium tetroxide. There was no discussion for titanium dioxide. Thanks, --Smokefoot 01:55, 18 September 2007 (UTC)

But what is the benefit of a move? The header contains both names and manganese dioxide redirects here. The current title is IUPAC preferred and doesn't seem to present any problems as a title since, except for one other line, the text of the article refers to the compound as "MnO₂" which can be read however one wishes. — AjaxSmack 07:35, 18 September 2007 (UTC)

In response - what is the benefit of the primary name being more appropriate? This decision is not super important, but in the scheme of things, it seems that our priority would be to have the most useful and common name as the title and subsidiary names redirecting to that one name. One could have calcium(II) chloride as the master name and calcium chloride direct to it, so what's the problem with that? Nothing except that the hierarchy of the redirects makes a statement of prioritizing names - legacy naming vs the appropriate name, orthodoxy (IUPAC) and who got there first - or appropriateness. WE-chem has fairly consistently come down on not supporting IUPAC since the naming is unconventional and nonintuitiive, not to mention unused. But I sense that I am losing this argument. Oh well...--Smokefoot 13:15, 18 September 2007 (UTC)

I wasn't opposing the move request, just seeking more information. I was surprised that Wikipedia does not have a more fixed policy on naming but that's probably OK. Without clear guidance, WP:COMMONNAME is a good enough reason for the move. After all, the redirect argument works both ways. — AjaxSmack 19:24, 18 September 2007 (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.

Electrical Conductor or insulator?

Is metal oxides are electrical conductors rather than insulators?--Tohyf (talk) 04:08, 29 November 2007 (UTC)

NFPA Rating

OK, so I checked 3 different MSDS (Sigma Aldrich, J.T. Baker, Alfa Aesar). All differ in their NFPA rating: Sigma Aldrich: 0-0-0, J.T. Baker: 2-0-1 and Alfa Aesar: 2-0-2 Some confusion stems from the fact that some companies use a system that it very similar to NFPA. J.T. Baker calls theirs SAF-T-Data. In that system the rating is 3-0-3. But this is NOT the NFPA rating and should not be confused with it. I will change to 2-0-1.Xenofonos (talk) 20:56, 22 April 2008 (UTC)

Yes, I think this is a fairly general problem, but probably exacerbated in this case by the fact the MnO2 can be anything from fairly dead (pyrolusite) to a pretty reactive oxidant. I'll raise this with User:Physchim62, who is trying to bring some semblance of order to our safety data (though I think he hates NFPA ratings for precisely this reason!). Walkerma (talk) 02:23, 23 April 2008 (UTC)

Indeed I do! Sometimes NFPA 704 values can be found on the International Chemical Safety Card, but in this case they haven't been included. Health=2 seems a bit high to me, I would have classified it as a 1-0-1-OX, but this just goes to show the problems with the system: who do we believe?! Physchim62 (talk) 11:46, 23 April 2008 (UTC) Indeed, Reactivity=0 would also be reasonable for most forms of manganese dioxide, although the fact that it is an oxidant does make it more dangerous in certain fire circumstances (NFPA 704 is specifically designed for firefighting hazards). Physchim62 (talk) 17:27, 23 April 2008 (UTC)

Having just bought some Manganese dioxide from Spectrum Chemical, the label reads Health: 2, Flam 0, Reactivity 0, and the MSDS i printed out from "sciencelab.com" says 2,0,0 . These are some BIG discrepancies from what wiki reports (1,1,2 OX). From what I can tell this is a simple metal oxide, not likely to be an oxidizer. I think this should be corrected to 2,0,0. Also, ANY metal powders are dangerous in fire situations. 209.65.161.128 (talk) 15:11, 13 December 2011 (UTC)[user: A.DiNunno, chemist, Matco Services)209.65.161.128 (talk) 15:11, 13 December 2011 (UTC)

Have been doing some research into fire hazards of manganese dioxide, and this is the only location an NFPA fire hazard rating of 1 is given. This in spite of all comments above stating flammability = 0. Hoping to elicit discussion to confirm to correct the rating prior to making an arbitrary change. Oh, also, should a flash point be listed? Every definition of "flash point" I've ever read indicates it's a property of liquids, not solids. (not sure why my ISP and date info is not automatically being appended. 14:00, 20 October 2014).

Melting point

The melting point of MnO2 is specified to be 535C which is significantly lower comparing with other metal oxides. If possible, please provide references confirming this data.

If possible, please provide details on the decomposition process taking place at the melting point. Especially the reaction products are of interest. LSH0607 (talk) 12:59, 20 August 2009 (UTC)

It's not really a "melting point" but a decomposition temperature. The figure of 535 ºC seems to come from WebElements, although Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0462-8. gives the same figure. Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1219. ISBN 978-0-08-022057-4. gives "about 530 ºC". The decomposition products are oxygen and manganese(III) oxide (Mn₂O₃). If you heat Mn₂O₃ even further (to about 1000 ºC), you will get Mn₃O₄. Physchim62 (talk) 13:46, 20 August 2009 (UTC)

Mechanism of the decomposition of hydrogen peroxide catalysed by manganese dioxide

Manganese dioxide also catalyses the decomposition of hydrogen peroxide to oxygen and water:

2H₂O₂ → 2H₂O + O₂

2H₂O₂ + MnO₂ → 2H₂O + MnO₄

MnO₄ → MnO₂ + O₂ (the catalyst is regenerated)

The hereabove mentioned reaction was written without care and its electrical balance was incorrect. I have properly balanced the reaction, but I have no idea if the MnO₄ substance [implying Mn(VIII)] really exists or is sufficiently stable to be handled in the lab. Not to be confused with the permanganate anion: MnO₄^–. In the doubt, I have not deleted this dubious equation, but it should be carefully checked. Thanks for your help. Shinkolobwe (talk) 16:55, 16 May 2010 (UTC).

Use of managanese dioxide by early humans

This section was deleted; I think it has value, but I didn't want to just re-add it. I'm not sure how these things are done. This was the deleted section (of course it's in the changelog too).

Manganese dioxide is believed to have been used in prehistoric times to start a wood fire. MnO₂ lowers the combustion temperature of wood from 350 degrees Celsius to 250 degrees Celsius. Manganese dioxide powder has been a common find in Neanderthal archaeological sites. <ref> http://www.nature.com/articles/srep22159 </ref><ref> Heyes, P. et al., Selection and Use of Manganese Dioxide by Neanderthals. Scientific Reports 6 (22159 ), doi:10.1038/srep22159 (2016) </ref>

Intrepidus (talk) 15:28, 3 March 2016 (UTC)

Thank you for raising this issue, the section appears to have migrated to the article manganite, which is about the mineral form of MnO₂. --Smokefoot (talk) 16:43, 3 March 2016 (UTC)

Second the idea that this information should be in the manganese dioxide article. I added it myself, then after seeing in the history that it had already been added and deleted I deleted my edit, which pointed to the same article. If there is a section on its use as a pigment by early humans--and there should be, then use as a fire starting aid should definitely be included, as well. As the paper reports, the use of manganese dioxide to lower combustion is cognitively much higher on the scale than is its use as a pigment even if those using it were not specifically aware that the combustion point was being lowered. grifterlake (talk) 06:37, 4 March 2016 (UTC)

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Cave painting and Neanderthal stuff

We might move that material to pyrolucite, since the cave people used the mineral not refined form of MnO2 for their artwork.--Smokefoot (talk) 13:53, 26 July 2018 (UTC)

I just moved the history and neanderthal content to pyrolucite.--Smokefoot (talk) 14:46, 29 July 2018 (UTC)

Strange mineralogy

Natural manganese(IV) oxide occurs as three polymorphs: pyrolusite, RAMSDELLITE and AKHTENSKITE. Hollandite not only bears BARIUM in addition to manganese, but its structure is actually a separate case. References: (1) https://www.mindat.org/min-3359.html; (2)https://www.mindat.org/min-71.html; (3) http://cnmnc.main.jp/; (4) https://www.ima-mineralogy.org/Minlist.htm Eudialytos (talk) 19:36, 29 September 2021 (UTC)

Endothermic or endoergonic?

In the section "Reactions", sub-section "Reduction", one can read: "As a source of hydrogen chloride, Scheele treated sodium chloride with concentrated sulfuric acid.

E^o (MnO 2(s) + 4 H+ + 2 e⁻ ⇌ Mn²⁺ + 2 H 2O) = +1.23 V

E^o (Cl 2(g) + 2 e⁻ ⇌ 2 Cl⁻) = +1.36 V

The standard electrode potentials for the half reactions indicate that the reaction is endothermic at pH = 0 (1 M [H+

]), but it is favoured by the lower pH as well as the evolution (and removal) of gaseous chlorine".

My doubt is that the standard potential data do not indicate that the reaction is endothermic, but endoergonic, that is, with a positive value of the standard Gibbs' free energy variation ∆G°. Ekisbares (talk) 17:37, 14 June 2024 (UTC)

Good catch, this had been wrong since 2010 - just fixed. Preimage (talk) 13:58, 11 October 2024 (UTC)