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Topic: Making Potassium Permanganate  (Read 7731 times)

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Offline Archy12345

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Making Potassium Permanganate
« on: February 17, 2013, 04:38:47 AM »
I've got plenty of MnO2 sitting around from batteries and such, and I want to try to make it a little more useful for organic reactions by making KMnO4.

I've heard of the common method for doing this by reacting dry MnO2 and dry KOH in air, but I don't have any KOH. I do however have lots and lots of KNO3.

I'm thinking of trying to do this electrolytically....
NO3- + 3e-  :rarrow: NO + (2O2-)
MnO2 + (2O2-:rarrow: MnO42- + 3e-

The NO bubbles off, and I'm left with K cations and permanganate anions.

If I use the manganese (IV) oxide as the anode, and then a carbon cathode, will this work?

Offline 408

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Re: Making Potassium Permanganate
« Reply #1 on: February 17, 2013, 06:32:01 AM »
The KOH method is fun!

Melt KOH over a torch, add MnO2 and KClO3.  Air oxidation is inefficient on anything except industrial scale.  You now have green potassium manganate.  Dissolve in water and add CO2 giving permanganate.  recryst.

Offline Archy12345

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Re: Making Potassium Permanganate
« Reply #2 on: February 17, 2013, 01:23:55 PM »
I don't have access to KOH though. That's my problem.

Offline billnotgatez

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Re: Making Potassium Permanganate
« Reply #3 on: February 17, 2013, 04:44:43 PM »
There are 2 links in this forum that suggest common sources.

http://www.chemicalforums.com/index.php?topic=8715.msg82682#msg82682
http://www.chemicalforums.com/index.php?topic=9326.0

Additionally, this site off this forum suggest some common sources (I used GOOGLE).

http://askville.amazon.com/primary-potassium-hydroxide/AnswerViewer.do?requestId=14780183

Notice that searching here sometimes gets you answers
and using GOOGLE and WIKI can also help (please read forum rules).

The problem with using some of the commercial products is you may have impurities. Using GOOGLE to find the MSDS can help to discover the impurities. You could use your knowledge of chemistry to reduce the impurities in commercial products.



Offline Wastrel

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Re: Making Potassium Permanganate
« Reply #4 on: February 19, 2013, 11:33:54 AM »
Potassium nitrate will work instead of KOH and it will contribute some oxygen, I think the reaction produces a lot of toxic NO2.  I'll add the details when I find them.  You may find that battery MnO2 contains a lot of graphite.

Offline Wastrel

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Re: Making Potassium Permanganate
« Reply #5 on: February 21, 2013, 05:14:58 PM »
I can't edit my previous post.

Mellor says fusing 1.5 parts KNO3 with 1 part MnO2 produces the manganate salt.  Water and CO2 will cause this to disproportionate as 408 said, filter MnO2 and separate permanganate and carbonate by fractional crystalisation.

Expect and plan for a lot of toxic NO/NO2.  Any carbon in the mix may cause significant problems.

Offline vmelkon

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Re: Making Potassium Permanganate
« Reply #6 on: February 25, 2013, 10:28:16 AM »
Just make sure you don't use battery MnO2 and NaOH.
Since I did not have KOH, I used NaOH. The MnO2 came from alkaline battery and the source of oxygen is KNO3. Nothing happened.

There is a long thread at sciencemadness.org. You need to clean the MnO2.
https://www.sciencemadness.org/whisper/viewthread.php?tid=8480

I don't know about the electrolytic method.

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