Sciencemadness Discussion Board

Cleaning chromium(III) oxide stains from a flat bottom flask

andyloris - 22-10-2022 at 08:52

I tried disolving chromium(III) oxide in hydrochloric acid, however it didn't work and I was left with chromium(III) oxide stains in my flat bottom flask.

How do I clean them ?

Thanks in advance !

andyloris - 29-10-2022 at 09:15

Guess my flask is gonna stay green forever ...

Bedlasky - 29-10-2022 at 09:27

I don't have experience with this issue, but when I needed clean something from Fe(OH)3, oxalic acid always worked very well. Try that. Or maybe bleach will help - it oxidize Cr2O3 to water soluble chromate. If Cr2O3 is deposited as a thin layer on the glass, you can try 40% NaOH - it eat away very small amount of glass and Cr2O3 won't stick to it anymore (and maybe even dissolve in NaOH).

clearly_not_atara - 29-10-2022 at 10:20

Could try forming the oxalate complex with refluxing potassium hydrogen oxalate?

andyloris - 29-10-2022 at 12:21

Thanks !

macckone - 31-10-2022 at 08:55

If hypochlorite does not work, there is always chlorate and bromate.
Depending on how tenacious the chromium oxide is, bromate may be the agent you need.