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Author: Subject: How to remove brown stains off beaker
TriiodideFrog
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[*] posted on 15-11-2020 at 00:59
How to remove brown stains off beaker


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TriiodideFrog
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[*] posted on 15-11-2020 at 01:02


There seem to be some brown stains on the bottom of my beaker. Does anyone know how to remove it? Thanks in advance.
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EthidiumBromide
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[*] posted on 15-11-2020 at 01:20


If there was a concrete chemical causing these stains, then it would be easier to tell if there was a chemical method of removing the stains (for instance, stains from KMnO4/MnO2 easily come off with a mix of vinegar and 3% H2O2).
But being generic, see if you can brush them off with an old toothbrush or something like that.

[Edited on 15-11-2020 by EthidiumBromide]
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B(a)P
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[*] posted on 15-11-2020 at 02:10


What caused the stains?
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MidLifeChemist
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[*] posted on 15-11-2020 at 09:52


Soaking overnight in dilute hydrochloric acid has cleaned every stain on glassware I've had so far. But my stains are usually from metal salts. Iron (III) compound stains are often brown.

Unless I know the stain is from Iodine, then I use a Sodium thiosulfate solution. Iodine stains are often brown.

Of course, if it an organic material, Acetone may do the trick.

Good luck!

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DraconicAcid
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[*] posted on 15-11-2020 at 10:23


If it's organic, but acetone does not do the trick, a small amount of boiling nitric acid will rip it off like a bandaid. Just make sure you've got a fume hood.



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TriiodideFrog
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[*] posted on 26-11-2020 at 18:20


Thanks for the advice! The dumb brown stain came off. I think its a mixture of lithium salts and something organic.
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aromaticfanatic
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[*] posted on 26-11-2020 at 21:48


In case anyone else has issues, letting a hot NaOH solution sit in the glass will do the trick. It eats away a thin layer of the glass essentially creating a new surface.



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[*] posted on 27-11-2020 at 03:05


Quote: Originally posted by EthidiumBromide  

(for instance, stains from KMnO4/MnO2 easily come off with a mix of vinegar and 3% H2O2).
[Edited on 15-11-2020 by EthidiumBromide]


Actually very diluted mixture of H2SO4 and H2O2 (few mls of each per liter of water) is potent enough to remove not only MnO2 but PbO2, Fe(OH)3 and many other (transitional) metal oxides. Put there and check in a day.

[Edited on 27-11-2020 by teodor]
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Bedlasky
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[*] posted on 27-11-2020 at 03:39


Teodor: I had issues remove iron even with conc. HCl. Oxalic acid is the best for removing iron oxides.



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