avliet
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Is it possible to "rescue" KOH from K2C03?
Hello all,
As the subject line asks - is it possible to re-create or "rescue" KOH from K2CO3? If so, how?
I've got a big pile of (formerly) KOH that was let sit out unprotected from air and moisture, and I'd like to know what it would take to reformulate
it into KOH - if at all possible.
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Neil
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"Historically KOH was made by boiling a solution of potassium carbonate (potash) with calcium hydroxide (slaked lime), leading to a metathesis
reaction which caused calcium carbonate to precipitate, leaving potassium hydroxide in solution"
...goooo google. Search took 0.18 seconds.
http://en.wikipedia.org/wiki/Potassium_hydroxide
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avliet
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@Neil Thanks for the attitude - much appreciated.
Considering that I've seen all sorts of things online and run into several sets of bad instructions from "reliable" Youtube videos and other how-to
sites lately, I thought maybe I should come to a science based forum and ask for the info more directly. Didn't think my relevant, reasonable
question would prompt such a dick move.
Sorry to have wasted your 0.18 seconds.
Anyone else interested in having an intelligent discussion with someone whom would like to actually /learn/ what's going on in this process and maybe
how to perform the reaction safely?
Thank you.
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Neil
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If by how-to sites you mean E-How - it is nothing more then a larger and less researched version of the anarchist cook book.
As for using a search engine...
http://www.sciencemadness.org/talk/viewthread.php?tid=13487
http://www.sciencemadness.org/talk/viewthread.php?tid=14450
Of course you still have absolutely no idea how reliable their information is. Just because it's posted on a science forum does not make it
scientific, so even if you post and are answered you have no idea how safe/stupid/sane their information is.
Unless you spend time reading past posts by the reliant individuals you'll be little better then you were when you were trusting kewls on youtube.
Interestingly the best way to do this is to use a search engine....
Edit: No worries it was a well spent 0.18 seconds.
[Edited on 13-6-2011 by Neil]
[Edited on 13-6-2011 by Neil]
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UKnowNotWatUDo
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May I ask why you are intent on trying to reuse this particular KOH? I promise it will almost certainly be way more trouble than it's worth. If it has
already completely turned to potassium carbonate then the best way to remake the KOH would be to mix it with another hydroxide. Preferably one that
would precipitate out the carbonate with the cation from your hydroxide salt. The best example I can think if would be, as Neil already said, calcium
hydroxide. I can pretty much promise you that this will not be worth your time or efforts as the best case scenario is you end up with a dilute
solution of KOH contaminated with calcium carbonate.
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woelen
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I agree with the previous post. It is easier and cheaper to buy new KOH. You can keep this old stuff as a nice source of K-ions or as a generic medium
high pH compound. But for applications requiring pure KOH you best buy new.
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avliet
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@Neil, @UKnoNotWatUDo, @woelen,
Thank you for the input.
One would think that there should be a reasonably cheap, effective way to do this if commercial enterprises are doing essentially this process
already.
That said, I don't have time to mess with building up a process to do the job, so I'll take your advice(s) and pick up some more uncontaminated KOH.
@UKnowNotWatUDo,
The reasons I would prefer to use the current material are 1) it's available, and I have a significant quantity of it 2) KOH isn't exactly "cheap" 3)
It's a material I'll either have to store, give away, or dispose of otherwise, and having no use for Potassium Carbonate in particular, I would rather
convert it (if possible) to something useful than pay to dispose of it or spend time and effort that I don't really have hunting for someone whom
needs it.
@Neil,
My apologies for going a bit off the handle earlier. Your comment was relatively benign and, low blood sugars or not, it didn't warrant such a strong
response. My apologies - I trust your intent was well meaning.
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Neil
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There are cheap and effective ways to do this, same with the Haber process, Ostwald process, lead chamber process... You just need to do it
in several ton amounts several times a day 
Good luck and Welcome, no offense meant or taken.
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bbartlog
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You need a fairly dilute solution in order for the reaction to proceed. According to 'The soap maker's handbook':
'For the preparation of perfect caustic lyes, the potassium carbonate has to be dissolved in 10 to 12 parts of water, and the sodium carbonate in 8 to
10 parts..'
So your procedure would be to dissolve the K2CO3 in twelve times its weight of water, heat it to 80-90C, then in small portions add a stoichiometric
amount or slight excess of finely powdered Ca(OH)2 (some old sources say Mg(OH)2 contamination is actually beneficial) while stirring each time. Then
filter (or allow to settle and decant) and boil off the liquid with exclusion of air.
The sticking point that stops me from trying this reactio, has always been drying and pelletizing (or otherwise crushing) the final product. I have
both K2CO3 and Ca(OH)2, and while the reaction is wasteful of both time and fuel (look how much you have to evaporate) compared to just buying KOH, it
would be nice to have some KOH that I made myself from wood ashes and agricultural lime. However, it is both very hard to dry and seems likely to form
a fused cake if I just heat it to fusion and let cool, so until I have some better idea of how to turn it into a powdered or granular form after
drying I'll leave it.
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woelen
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Quote: Originally posted by avliet  | | One would think that there should be a reasonably cheap, effective way to do this if commercial enterprises are doing essentially this process
already. |
This argument is brought up here before, e.g. for making H2SO4, HNO3, NaOH. The problem is that
industrial processes are amazingly hard to copy at a small scale in the lab, or even at home. Often these industrial processes are based on a lot of
clever engineering, a lot of heat and power management and the chemistry behind them usually only is a small part of the total working of the plant.
Just go to some area where there is a lot of chemical industry and have a look at the buildings with all the pipes, pressure outlets and whatever
more. They look very complex and they _are_ very complex.
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avliet
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Ah yes, the old economy(ies) of scale perception of reality. From mega factories to supertankers - always easier to do things "en mass".
That, or as you say - some /very/ clever engineering. Genetically modified Algae that excrete oil for conversion to B100, for example..?
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