RogueRose
International Hazard
Posts: 1593
Registered: 16-6-2014
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Drying KMnO4 (clumpy from humidity)
I am wondering if there is any special method that needs to be used to dry ~98+% KMnO4 that has gotten wet either from very slight water leakage or
from very high humidity. It used to be free flowing crystals and now I've been told that it is caked together in clumps (that can be broken up, it is
not a solid crystal).
Also, does this degrade the product much?
It is in a VERY thick 5 gallon bucket that seals perfectly tight. I was considering using one of those heat tapes (wrap pipes with them in the
winter) as I have 2 250w and 3 300W and 2 150w units so I could get a variety of wattages (all 110V). I figured I could wrap the bucket wit the
silicone heat tapes (surrounded by blankets of fiberglass insulation) and put a 1/4" hose barb on the lid attached to a vacuum. Then heat the bucket
to maybe 130-160F or more (decomp at 464F) and then draw vacuum at same time.
I could also have 100% dry air ready to push back into bucket when vacuum is turned off.
Another option is to dry air completely (run through my -20F freezer, then through dessicant) and then pump air through the bucket. This might
actually be easier though IDK. IDK if heating the bucket along with this cold dry air would draw out the most water and I wouldn't need to worry
about drying the air before it gets to the vacuum pump (not aspirator).
Any thoughts on this?
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woelen
Super Administrator
Posts: 8013
Registered: 20-8-2005
Location: Netherlands
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Mood: interested
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Just allow it to dry in a dish in a warm place (50 C or so).
Your KMnO4 most likely will have degraded a little bit. When it becomes humid, it slowly decomposes, giving MnO2, O2 and KOH. The KOH in turn is
converted to K2CO3 by CO2 from air.
If you make it perfectly dry again, then the degradation process will stop and if this process did not goo too far already, then the product still
will be perfectly fine for most uses.
I myself have a bottle of NaMnO4 and this has absorbed a lot of moisture from air and hardly any permanganate is left. Nearly 100% is converted to
MnO2 and Na2CO3. But, NaMnO4 is MUCH more sensitive to this kind of degradation than KMnO4. Yours most likely will still be fine.
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