I am using the KMnO4 method for estimating active carbon. My problem is that my glassware gets stained with I believe manganese oxide. Bleach doesn't remove it. Any ideas on how to get my glass ware clean again? And would it influence my results if I used the stained glass ware?
Only cleaning agent (with care!) would be concentrated hydrochloric acid. If this doesn't work, then throw away the glassware and buy new.
It is better use the same reaction type. It is oxidesed Mn then add some reducing agent to make it soluble. For example oxalic acid solution can be used.
The reason for stain formation in glassware surfaces is oxidation of MnO4 to MnO2. Therefore any chemical reaction dissolving the MnO2 can clean stains. Best chiase would be some asit addtion along with a reducing agent such as oxalate.
Ideally use hydroxylammonium sulfate ( a crystaline water soluble powder) as it reduces Manganese dioxide in its water soluble form.
https://www.researchgate.net/profile/M_Farooq_Wahab/post/KMnO4_staining_glass_ware_How_do_I_get_rid_of_it_manganese_oxide_I_believe/attachment/59d649b179197b80779a4224/AS%3A472199665590272%401489592581216/download/Glassware+Cleaning_Farooq.pdf
Thanks. This acidic H2O2 mix that M. Farooq Wahab recommended works wonders.
I put citric acid crystals in the stained utensi then added water and microwaved Till water was warm.
then I scrubbed it with lemon and let it sit for an hour.
got rid of the stain
Great, thanks. I must say the acidified H2O2 falso works well, but maybe your method is less hazardous.
Anélia Marais Hi Marais, could you please provide the protocol of H2O2 method? I reach the same problem, that method would be useful for me. Thank you
@ Van-Sieu Luc I tried to find the original article but could not. It is somewhere on this chat. Though, what I use is 3% H2O2 and then add a few drops of HCl. On around 4 litres that I make up, maybe 1ml of concentrated HCl. This cleans quite a lot of plastic and glassware. You can even use it for more than one batch of glassware over and over. You will see when it loses its 'strength'.
Use boiling water to remove mno2 then dip in acid bath for 1h and again in base bath for 1hr your glass apparatus will be cleaned completely from mno2
use any reducing agent like sodium bilsulfite/metabisulfite dissolve in water
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