Micha
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KMnO4 crystals
Has anybody managed to grow a single crystal of KMnO4? Couldn't find much on the internet, sorry if this is repost, I am new here.
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LearnedAmateur
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Welcome to the forums, AFAIK you can't create a crystal of KMnO4 from aqueous solution because it will decompose. I made a Christmas tree decoration
using it once, a layer of green KNaMnO4 solution (addition of NaOH) on top of the purple solution. After a few days it had completely broken down
leaving a clear solution and brown-black precipitate of MnO2.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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unionised
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When you buy permanganate, what do you think it was crystallised from?
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Micha
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Well, what if you would paint them with transparent nail polish? It decomposes in water solutions to MnO2, and to decompose it to K2MnO4 you would
need some heat , alkali solution. I am anyway going to try it, I just want to know if someone tried it yet.
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Micha
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Well, as I think of it now, as you would wait for bigger crystals to appear, it would decompose in water solution into MnO2
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LearnedAmateur
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I'd always thought that water was removed during the synthesis from manganate, generating the solid that way. Like I said, in my experience it is
unstable in aqueous solution, at least at low concentrations anyway (low enough to be able to see through without shining a light).
All the permanganate products I've seen either come as a coarse powder, which is how I got it, or small crystals. I guess it could be crashed out of a
hot solution upon cooling as opposed to the usual method of crystal growth, letting the water evaporate over a period of days/weeks? I've never come
across a single crystal larger than a few millimetres, have you? I'd like to be proven wrong, as it would certainly be a cool crystal to own!
[Edited on 18-12-2017 by LearnedAmateur]
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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mayko
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I got these trying to purify some grungy eBay koi treatmen; there might have been some minor decomp but the main thing I learned was that filter paper
doesn't stand up to hot, concentrated permanganate 
 
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unionised
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Potassium salts- like permanganate and dichromate- are often preferred over the sodium for laboratory use even though they are more expensive, because
they generally have steeper solubility curves and are therefore easier to purify by recrystallisation
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