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Author: Subject: Purifying Potassium Permanganate
Meltonium
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[*] posted on 25-9-2016 at 15:49
Purifying Potassium Permanganate


So recently I ordered about 1.5kg of potassium permanganate off of Amazon. I read the MSDS for the product from the supplier and it says 60-100% KMnO4 with sodium sulfate contamination accounting for the majority of the other percentage. I tried to recrystallize some of it but there was a lot of MnO2 residue from the recrystallizing dish. Is there any way I can separate the Na2SO4 and the KMnO4 without a lot of decomposition?
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Texium (zts16)
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nezza
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[*] posted on 25-9-2016 at 23:38


Potassium permanganate is much less soluble in water than Sodium sulphate so initially I would try washing it with a few changes of slightly acidulated water (a drop of two of sulphuric acid to keep the pH down). Then you can try recrystallising it again in slightly acidulated water. KMnO4 is not very soluble in water (a couple of hundred grams per litre in hot water) so assuming you end up with 700g of KMnO4 you should try 2 or 3 l of water for the recrystallisation. Try doing these on a sample first with scaled down amounts to make sure it will work before committing the lot.



If you're not part of the solution, you're part of the precipitate.
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Deathunter88
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[*] posted on 26-9-2016 at 00:40


In my experience when an MSDS lists 60-100% of some ingredient they are purposefully being vague. If you look up some MSDS's for paint thinner some of them say "60-100% Hydrotreated light distillate (petroleum)." But really if you think about it what other thing can be part of paint thinner? So I think that the product you bought can be used as is, unless there is another reason for you to suspect high contaminations (color etc.) A link to the actual MSDS would be helpful though.
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byko3y
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[*] posted on 26-9-2016 at 03:16


If manganese dioxide precipitate is a problem, then you can just filter the solution using a sinistered glass filter.
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wg48
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[*] posted on 26-9-2016 at 06:12


Washing with even very dilute acid is very likely to make more manganese dioxide as it would produce permanganic acid which decomposes to manganese dioxide.

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[*] posted on 26-9-2016 at 06:46


I think acetone might be your answer. Try dissolving some in a minimum of acetone filtering and evaporating.
Low solubility would require an awful lot though.
Got a Soxhlet? perhaps you could leach it out with a Soxhlet, under partial vacuum if needed.

Sodium sulphate might only be common in those permanganate products described as "free flowing' . Perhaps you can find one without this anti-caking agent in it.

Or you could even try buying an actual reagent instead of a can of green sand filter regenerator, or whatever you bought.

Depending on just what you want it for, you might not need to eliminate the sodium sulphate.

[Edited on 26-9-2016 by Maroboduus]
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[*] posted on 27-9-2016 at 12:38


Amazon also sells Black Swan permanganate, which according to the company is 97% Potassium permanganate. A 3lb bottle is around $45 US.
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[*] posted on 27-9-2016 at 13:10


Depending on intended usage, just use it as-is.

What is the intended purpose that requires it to be free of sodium suphate ?

Alternatively, buy purer material off ebay :-

http://www.ebay.co.uk/itm/100-g-Potassium-permanganate-Kaliu...

It's not expensive enough to mess about with, although messing about with things is what it's all really about.




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[*] posted on 18-1-2020 at 03:32


@Meltonium - I know this is an old thread of yours, but did you ever find a decent way to purify the KMnO₄? I just purchased 2 pounds of technical grade, looking for a good way to purify it as well.

Quote: Originally posted by Maroboduus  
I think acetone might be your answer. Try dissolving some in a minimum of acetone filtering and evaporating.
Low solubility would require an awful lot though.
Got a Soxhlet? perhaps you could leach it out with a Soxhlet, under partial vacuum if needed.[Edited on 26-9-2016 by Maroboduus]

Using acetone and a soxhlet extractor seems like an interesting idea. You thinking just let the soxhlet run and eventually some purified KMnO₄ will precipitate out of the acetone in the bottom flask as it gets overly saturated? I may give this a shot ;)

Thanks!
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[*] posted on 18-1-2020 at 04:23


Quote: Originally posted by SuperOxide  
Using acetone and a soxhlet extractor seems like an interesting idea.


I could be worrying for nothing but heating acetone with potassium permanganate sounds like a potential fire bomb :o




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[*] posted on 18-1-2020 at 06:21


Quote: Originally posted by Sulaiman  
Quote: Originally posted by SuperOxide  
Using acetone and a soxhlet extractor seems like an interesting idea.


I could be worrying for nothing but heating acetone with potassium permanganate sounds like a potential fire bomb :o


I second that.

Also, the OP has probably sorted it out in the intervening few years.
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DavidJR
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[*] posted on 18-1-2020 at 08:26


Quote: Originally posted by Sulaiman  
Quote: Originally posted by SuperOxide  
Using acetone and a soxhlet extractor seems like an interesting idea.


I could be worrying for nothing but heating acetone with potassium permanganate sounds like a potential fire bomb :o


I've distilled acetone from potassium permanganate before and it's fine.
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[*] posted on 18-1-2020 at 10:30


Quote: Originally posted by DavidJR  
Quote: Originally posted by Sulaiman  
Quote: Originally posted by SuperOxide  
Using acetone and a soxhlet extractor seems like an interesting idea.


I could be worrying for nothing but heating acetone with potassium permanganate sounds like a potential fire bomb :o


I've distilled acetone from potassium permanganate before and it's fine.

So have I. It's a good way to strip (some) impurities out of the acetone.
But the relevant question is "Have you distilled acetone from permanganate that contains unspecified impurities?".
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