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Author: Subject: Sintered Funnel Clogged with Cr2O3
jwrigly
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[*] posted on 7-8-2019 at 04:14
Sintered Funnel Clogged with Cr2O3


I've managed to clog one of my sintered funnels with Chromium Oxide. I've tried putting conc NaOH and conc HNO3 through it but there was no change. Is it possible to dissolve Cr2O3, or convert it into something soluble?

I've read that it should react with conc acid/alkali to produce complex ions. Does the acid / base need to be heated? Or is it a very slow process?
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ZetekitoxinAB
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[*] posted on 7-8-2019 at 13:14


Maybe try adding dropwise conc NaOH and 30% H2O2 alternately ? Perhaps the energetic decomposition of the hydrogen peroxide would help cleaning out the particles and maybe also convert Cr2O3 into soluble chromate. It might damage the funnel though, I am not sure.
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TheMrbunGee
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[*] posted on 7-8-2019 at 14:06


Quote: Originally posted by ZetekitoxinAB  
Maybe try adding dropwise conc NaOH and 30% H2O2 alternately ? Perhaps the energetic decomposition of the hydrogen peroxide would help cleaning out the particles and maybe also convert Cr2O3 into soluble chromate. It might damage the funnel though, I am not sure.


Looks like jwrigly does not have H2O2.

Try pushing water or soap water trough the filter form bottom, that may release some particles stuck.

Then you may leave some alkali solution to sit for few days in the funnel, maybe gravity drip alkali solution trough. Remember, that strong alkali solutions might damage the sintered glass. You may increase the concentration following formula:
(alkali concentration = willingness to have a clean nice filter - possibility to buy new one - financial status)

Leave it for few days. You might never have a nice clean filter again, but from another perspective - it is just metal oxide, not carbon (in my case)


Good luck!

[Edited on 7-8-2019 by TheMrbunGee]




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XeonTheMGPony
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[*] posted on 7-8-2019 at 17:43


Soaking in warm solution is the trick to allot of such issues.
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DavidJR
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[*] posted on 8-8-2019 at 13:49


I'd try EDTA.
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AJKOER
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[*] posted on 18-8-2019 at 06:05


The problem is not so such on dissolving the Cr2O3, but on what to do responsibly with the toxic waste produced in the process. Either strong H2O2 or HOCl (from like vinegar + Chlorine Bleach) should work with time.

See my comments and sources together with all WARNINGS in this prior SM thread https://www.sciencemadness.org/whisper/viewthread.php?tid=18... .
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[*] posted on 18-8-2019 at 12:12


Quote: Originally posted by AJKOER  
The problem is not so such on dissolving the Cr2O3, but on what to do responsibly with the toxic waste produced in the process. Either strong H2O2 or HOCl (from like vinegar + Chlorine Bleach) should work with time.

See my comments and sources together with all WARNINGS in this prior SM thread https://www.sciencemadness.org/whisper/viewthread.php?tid=18... .


Convert it back to Cr2O3
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woelen
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[*] posted on 19-8-2019 at 02:18


What might help is slowly pouring a hot alkaline solution of NaBrO3 or KBrO3 through the funnel. Maybe it also works with conc. NaOCl, to which additional NaOH is added.
As others already pointed out, strong alkalies may damage the sintered glass somewhat.
After this treatment it is very important to rinse with distilled water in order to remove any leftover alkali.

If after this treatment some Cr2O3 remains behind, then you can simply use it with that material trapped in it. Cr2O3 is nearly as inert as the funnel itself and if it is trapped, then it will not contaminate anything which you pour through it.




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S.C. Wack
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[*] posted on 20-8-2019 at 13:17


Glass is much more soluble in alkali than Cr2O3. I have mentioned that KMnO4 with conc. sulfuric acid/drain cleaner dissolves/+6's even the most dead burnt pigment, and sometimes "MnO2" will as well, but AFAIK no one has monetized this information with video or prepchem, so it must not exist.



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