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Author: Subject: Removal of caked on MnO2 from round bottom flask?
itsallgoodjames
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[*] posted on 19-12-2020 at 16:16
Removal of caked on MnO2 from round bottom flask?


Is there an easy way to do this? I have been unable to wash it out with water, and I can't get a brush to reach all the inner surfaces. Thanks in advance for the help!

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Antigua
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[*] posted on 19-12-2020 at 16:21


Almost everything works... sodium bisulfite (so sodium metabisulfite too), dilute HCl, even some detergents with chelating agents apparentely.
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itsallgoodjames
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[*] posted on 19-12-2020 at 16:29


Oh, thanks. I wasn't aware it was so simple



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Bedlasky
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[*] posted on 19-12-2020 at 16:40


Oxalic acid or hydrogen peroxide are also good options.



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

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itsallgoodjames
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[*] posted on 19-12-2020 at 17:54


Doesn't MnO2 catalyze the decomposition of hydrogen peroxide?



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wg48temp9
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[*] posted on 19-12-2020 at 21:14


First try to remove the MnO2 by stuffing one or more plastic or foam scouring pads in to the flask. Then add sufficient water to swirl the pad around the flask or use a rod to force the pad/s against the surfaces that can not be reached directly. You may need a stout wire hook to fish the pads out when your finished.

PS: Yes H2O2 will be catalytically decomposed by MnO2.

[Edited on 12/20/2020 by wg48temp9]




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[*] posted on 19-12-2020 at 21:21


Vitamin C (ascorbic acid) will work just fine. Quick and easy to get from your local store too



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[*] posted on 19-12-2020 at 21:43


Quote: Originally posted by wg48temp9  
First try to remove the MnO2 by stuffing one or more plastic or foam scouring pads in to the flask. Then add sufficient water to swirl the pad around the flask or use a rod to force the pad/s against the surfaces that can not be reached directly. You may need a stout wire hook to fish the pads out when your finished.

PS: Yes H2O2 will be catalytically decomposed by MnO2.

[Edited on 12/20/2020 by wg48temp9]


Rather than a scouring pad, I'd use sand or rice. I've used them for years to clean out wine bottles (and the rice may act as a reducing agent, as well).




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[*] posted on 19-12-2020 at 21:48


Quote: Originally posted by Antigua  
Almost everything works... sodium bisulfite (so sodium metabisulfite too), dilute HCl, even some detergents with chelating agents apparentely.


Doesn't HCl form chlorine? I suppose in dilute solution none would really be released.




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[*] posted on 19-12-2020 at 23:37


Quote: Originally posted by DraconicAcid  
Quote: Originally posted by wg48temp9  
First try to remove the MnO2 by stuffing one or more plastic or foam scouring pads in to the flask. Then add sufficient water to swirl the pad around the flask or use a rod to force the pad/s against the surfaces that can not be reached directly. You may need a stout wire hook to fish the pads out when your finished.

PS: Yes H2O2 will be catalytically decomposed by MnO2.

[Edited on 12/20/2020 by wg48temp9]


Rather than a scouring pad, I'd use sand or rice. I've used them for years to clean out wine bottles (and the rice may act as a reducing agent, as well).


Sand will form microscopic scratches in the glass - not safe. Rice would be better.
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[*] posted on 20-12-2020 at 06:50


ive always used HCl to clean up MnO2. generates a bit of Cl2 but its extremely fast acting.
i guess metabisulfite would work well too, but havent tried
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[*] posted on 20-12-2020 at 06:59


Coarse salt and just enough soapy water to make it into a thick abrasive paste. Cap and shake, and it will remove hard crusty spots without damaging the glass like sand does. If you need it acidic, use dilute HCl. Works well even with organic solvents (e.g. black organic tars inside of RBFs), just use a chlorinated solvent or paint thinner instead of water.




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[*] posted on 20-12-2020 at 15:39


I would use HCl, and just do it outside if you don't want a dose of Cl2 up your nose. Good luck and let us know how it goes!
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[*] posted on 20-12-2020 at 17:01


Quote: Originally posted by itsallgoodjames  
Doesn't MnO2 catalyze the decomposition of hydrogen peroxide?


In neutral and alkaline solution yes. But in acidic solution it react with H2O2 to form Mn2+ and O2.




If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

"An old friend once told me something that gave me great comfort. Something he had read. He said that Mozart, Beethoven and Chopin never died. They simply became music." Dr. Robert Ford, Westworld
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[*] posted on 21-12-2020 at 05:50


Lemon juice also works- which is good to know if you get similar stains on your fingers.
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[*] posted on 28-12-2020 at 03:55


Some mild acids should work quite well.
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