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Hi Smee,
I make it up fresh each time. I use the recipe : 100mLs 0.01M KMnO4 + 17mLs conc Sulfuric acid. I just checked some I prepared on Wed, and it's gone clear already.
Cheers, Ellice.
It is better to make it fresh as oxidation with natural/artificial light will cause the Permanganate to be reduced to manganate (Brown) solution rendering the solution not fit for use.
Overnight storage can be performed by storing it in the fridge.
Cheers,
Robb.....
Dr Robert Crosdale. MRACI. NSS. NSSA. NASA.
Ph.D (Chem), Post Grad Ph.D (Physics), M.Ed, B.Sc (Hons), Dip. Appl. Sc. (Chem)
Lake Munmorah High School.
University of New England.
University of New South Wales.
University of Newcastle.
To understand the Universe from our perspective, we need to look towards our own backyard first for answers.
Make up the desired strength ie 0.01M and add a few squirts of concentrated acid. I actually can't remember whether I use HCl or H2SO4, maybe it doesn't matter.
I have done a search here and found a couple of recipes, but does anyone have a tried and true recipe for acidified potassium permanganate?
I need it for Friday, so should it be made up freshly on Friday morning?
TIA,
Helen
Regards
remlap12
science support and problem solver
My Chem teacher gets his students to acidify it themselves - 4mL 0.1M potassium permanganate (which I supply) and they add 2mL 1M sulfuric acid.
Too easy!
Hi. Just wanting to ask another question about this. What happens to the acidified potassium permanganate over time that necessitates making it up fresh? Does it just neutralise, so go back to unacidified, or does something else happen? Just wondering if I had some bottles of "acidified potassium permanganate" made up ages ago, can I just add some additional concentrated sulfuric acid to that freshly, or would that not work?
Also wondering, if this is not possible, what should I do with excess "acidified potassium permanganate" that is not able to be used anymore?
OK, have done a bit more research and I think it's the actual potassium permanganate that degrades over time. Does the acid accelerate this maybe? The non-acidified solution that we have is still nice and purple, but the dropper bottles labelled acidified are all clear with brown precipitate, so they're no good.
This from RiskAssess for KMnO4 >0.38M disposal - <60 mL/day may be diluted with 10 times the volume of water and poured down the drain. Larger volumes should be placed in a Manganese waste container.
Also from RiskAssess regarding the permanganate ion - Highly toxic to aquatic life, but reacts in sewer with organic
matter to form Mn(II) and MnO2.
For sulfuric acid <1.7M - <60 mL/day may be added slowly, with stirring, to 10 times the volume of water, then poured down the drain. Larger quantities should be placed in an Acid waste container.
So my advice is chuck it down the sink.
With regard to your original question of why this solution is made fresh - I have no idea. Hopefully someone will know and will post an answer.