Xenoid
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Potassium Manganite
Manganese compounds are a nightmare!
I am trying to get some information on potassium manganite (Ref. DerAlte's Permanganate thread) but I can't even find a consistant formula for this
chemical can anyone help? I have the following;
My copy of Mellor's Modern Inorganic Chemistry by Parkes;
Manganese dioxide, particularly in this form (hydrated, precipitated) reacts with alkali hydroxides to form manganites. Also when manganese dioxide is
fused with potassium hydroxide in absence of air, potassium manganite, K2MnO3, is believed to be formed. Calcium manganite, CaMnO3, was probably the
chief constituent of the "manganese mud" obtained in the (now obsolete) Weldon recovery process for chlorine.
Wikipedia;
Potassium manganite is the chemical compound with the formula K4MnO4. The brown-coloured manganite anion is a significant if often overlooked product
of the reduction of permanganate. This Mn(IV) species is produced by dissolving MnO2 in strongly alkaline solution. [MnO4]4- is the conjugate base of
the hypothetical acid Mn(OH)4. Alternatively, MnO44- can be generated by reduction of MnO43-.
A Blog Somewhere;
....the highest is given the prefix per as KMnO4 potassium permanganate, K2MnO4 potassium manganate, KMnO2 potassium manganite; the lowest valence
employs the prefix hypo- though sub was formerly used.
So we have K2MnO3, K4MnO4 and KMnO2 as formulae for potassium manganite.
Does anybody know the correct formula, I gather it is brown and insoluble.
Edit: To further complicate things "manganite" is a mineral ore of manganese, gamma MnOOH.
Regards, Xenoid
[Edited on 29-8-2007 by Xenoid]
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Sauron
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If I were you I would go with Mellor, and ignore Wiki and "some blog".
Stick to the chemical literature. Wiki is essentially web graffiti.
Here is an article from Industrial & Engineering Chemistry (ACS)
You might also wish to peek in Brauer's book in the forum library.
[Edited on 30-8-2007 by Sauron]
Attachment: ie50157a033.pdf (777kB)
This file has been downloaded 947 times
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Xenoid
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| Quote: | Originally posted by Sauron
If I were you I would go with Mellor |
Yeah! But unfortunately it's 50 years out of date. It was "Modern" in the 60's.
There has been a hell of a lot of chemistry done in the last 50 years, and I haven't really been part of it.
Regards, Xenoid
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Sauron
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Here's the link for ACS search (all their journals, all issues) for potassium manganite. First 100 returns out of a little less than 400, sorted by
relavence.
Every one of these can be accessed for free if only uou know the tricks taught in the References section.
http://pubs.acs.org/wls/journals/query/subscriberResults.htm...
[Edited on 30-8-2007 by Sauron]
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The_Davster
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Hmm, yes manganite seems very elusive, I have info on various oxoanions of manganese in the book in front of me (Housecroft and Sharpe, Inorganic
Chemistry), but unfortunatly, although it does cover the various oxoanions...they do not give names.
You know about permanganate and manganate, so what remains in this book is: (paraphrased)
[MnO4]3-:Blue and moisture sensitive, formed by reduction of permanganate in concentrated Na/KOH at 273K. Disproportionates manganate and MnO2 in
weakly basic solution and to permangante and MnO2 in acidic.
"[MnO4]4-":Reaction of Mn2O3 with CaCO3 at 1400K yield Ca2MnO4 which only formally contains [MnO4]4-, but its crystalization in a layered structure
each Mn(IV) centre is in octahedral MnO6 environment and isolated [MnO4]4- ions are not present.
This book seems exhaustive on manganese chemistry in tems of compounds, it even goes into permanganyl halides and manganyl halides, so would think
that 'manganite' is one of the compounds above. But I would not be completly surprised if it were not.
[Edited on 29-8-2007 by The_Davster]
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Xenoid
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| Quote: | Originally posted by Sauron
Here's the link for ACS search (all their journals, all issues) for potassium manganite. First 100 returns out of a little less than 400, sorted by
relavence.
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I had found the ACS site from your earlier post. The link you give does not include the search results. When I search for "potassium manganite" I only
get 27 (what appear to be) largely irrelevant results, how did you get 400!
Edit: The Brauer is great! I had been planning to download some of the books, this has spurred me on to doing it. No mention of manganites however!
Regards, Xenoid
[Edited on 29-8-2007 by Xenoid]
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Sauron
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1. set the boolean operators to OR instead of AND
2. Put "manganite" in the field for TITLE and ANYWHERE
3. Do not select journal or date range
4. Select 100 results (default is 10)
Click SEARCH
If you search for potassium manganite you get your 27 results, but I would not assume these are all irrelevant. As you can have them for free, what do
you have to lose? Just a little time like everyone on a peper chase.
Beats the hell out of Wiki and "some blog" anyway.
[Edited on 30-8-2007 by Sauron]
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DerAlte
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I agree with The_Davster. Being a transition metal nut, 'Manganites" are very hard to find believable information on. You'll find a whole sew of BS
in things like Ph D theses that purport to say important things, but there's no meat in them.
The Victorian chemists (Roscoe and Mendelyeev, e.g.) considered that there were a whole series of compounds of formula type RMnO2.{Basic anhydride}
with R an integer. The calcium manganite was produced in the weldon process for recycling the manganese otherwise lost in the process of Cl2
manufacture,
I have made the light blue hypomanganate Mn(V), MnO4- - - (Brauer describes how). It is not stable even at 0C and soon changes back to manganate(VI)
I have attempted to make Na2MnO3 with very strong NaOH (50%) and MnO2 but all I got a black substance that looks very much like the original MnO2
even on prolonged boiling. But the books say all manganites are black and insoluble.
Whatever they are, they are not of much general interest.
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woelen
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I also have been experimenting a lot with manganese, but I also never obtained anything, which satisfies the descriptions of manganite. I also read
things like MnO2 is amphoteric and dissolves in bases. Well, I tried it, but nothing at all, not even boiling bases.
The best I could obtain is a brown "solution", but I strongly suspect this to be a colloidal "solution". Also the blue manganate (V) has been elusive
for me. I tried to make this from KMnO4 in alkaline solution, and Na2SO3, but this gives a green manganate (VI) and after that, it becomes turbid and
brown.
I am inclined to think that manganite does not exist as soluble salt. Sure, there might be mixed oxides like CaMnO3, CuMnO3, but these are not the
interesting and water-soluble species I would expect. I lost my interest in the manganite stuff, simply because I believe they do not exist as soluble
salt, not even in 50% KOH or 40% NaOH.
Another interesting manganese (IV) species might be MnCl4, or complexes like MnCl6(2-). When you dissolve MnO2 in conc. HCl and keep this cool, then
you obtain a dark green/brown solution, which is clear. The same happens with KMnO4 in conc. HCl. Some chlorine is formed, and the manganese forms a
green compound in solution. The stuff definately does not easily go down to Mn(2+), as common text books suggest. On the other hand, when MnCl2 is
added to concentrated HCl, then no green solution is formed. I think this is a manganese (IV) species, also because, when it is formed from MnO2,
then no smell of chlorine can be observed. This is interesting stuff...
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not_important
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My references, some going back a half century or more, say that Mn(IV) is formed by dissolving MnO2 in concentrated hydrochloric acid, provided it is
kept cold. Heating or the laps of time leads to the production of Cl2 and Mn(II). KMnO4 in con. HCl can yield K2MCl6, supposedly adding concentrated
solutions of halides or sulfates to a cold solution of MnO2 in HCl can also form such salts.
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DerAlte
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MnO2 is usually said to be covalent O=Mn=O. As such is ought not to be basic, but older authorities sometimes call it "feebly" basic. 'MnCl4' always
looked deep brown to me, it is intersting to hear it can look green. Or is this part of the decompositon:
MnCl4 => MnCl3 (green, IIRC, rather unstable) => MnCl2 (pink, stable) (+Cl2 qt each step).
MnF4 is quite stable AFAIK. MnF3 is ar ed solid, reacts with H2O, decomposes at >600C(CRC). Compare MnCl3, which decomposes when heated in
solution.
Mn always seems to be unhappy unless surrounded by oxygen atoms! Eventhe Mn(II) salts are hard to keep from oxidation. As for manganites, as Woelen
says, if they do exist they are boring.
Regards, Der Alte.
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Xenoid
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| Quote: | Originally posted by DerAlte
As for manganites, as Woelen says, if they do exist they are boring.
Regards, Der Alte. |
There are quite a lot of references to manganites of the type A(1-x)B(x)MnO3 where A may be rare earths for example and B may be Sr, Ba etc. These
compounds are as Woelen says mixed oxides and can be formed by sintering the oxides at high temperature. They are apparently important
magneto-resistant compounds. But even here there is confusion, Woelen notes copper manganite (CuMnO3) but I also noted a reference to copper manganite
(CuMn2O4).
I am still confused!
Regards, Xenoid
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DerAlte
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I put them in the same class as ferrites (as used as magnetic materials) - basically just mixed oxides of manganese with some other metal. Or those
complicated silicates that many minerals are - some sort of intercrystalline structure that is homogeneous.
Regards, Der Alte
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