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mericad193724
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Potassium Hydroxide Synthesis
We all have easy access to NaOH crystals as drain opener, but it is much harder if not impossible to come across Potassium Hydroxide crystals OTC. KOH
is usually found as a very dilute solution of KOH in drain openers.
Would it be possible to make KOH in the following way:
KCl + NaOH --> NaCl + KOH
Potassium is more reactive then Sodium so it should displace it, right?
After this reaction KOH would need to be extracted and this would be difficult because boiling down a very concentrated KOH solution is not my idea of
fun. The KOH could be extracted with the use of Ether, since it is insoluble in it. (2 solvent recrystallization).
Would this work?
thanks
Mericad
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woelen
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No, this hardly will work. NaCl is slightly less soluble, so you could obtain a mostly KOH solution, but heavily contaminated with sodium chloride.
Making KOH from NaOH hardly is feasible.
One way to make KOH is to try to obtain CaO or Ca(OH)2 (some cement's contain this, albeit in impure form). Making a solution of this, and adding a
solution of K2CO3 does the job. CaCO3 is precipitated and KOH remains behind in solution. It should be possible to obtain reasonably pure KOH in this
way.
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mericad193724
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It seems that my proposed synthesis is impractical.
IIRC you can make CaO from CaCO3 by heating it to decomposition. (Coincidentally I made CaCO3 yesterday, 8 grams). Can I achieve sufficient
temperature to decompose the CaCO3 completely if I put the CaCO3 in a copper pipe end cap and heat strongly with a propane torch? This could be a
simple path to CaO.
Mericad
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stricnine
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Off my head, you need 1100ºC to decompose it into CaO. The propane flame should allow you to reach that temperature, but I am not so sure about the
heat loss of your pipe "crucible", nor how efficient is the torch.
But yes, it would be a practical and easy path.
I am getting old. I used to push it aside with one hand... now I need both!
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mericad193724
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I just tried taking 1 gram of Precipitated CaCO3 and heating it with propane on a ceramic wire gauze. First let me say DO NOT HEAT BARE WIRE GAUZE, it
will glow red, sag and crack a bit upon cooling. But after the CaCO3 weighed .76 grams. There was some CaO produced because trying to dissolve it in
water yield a solution with pH 13-14! Very little of the solid dissolved. I only heated for about 5 min.
Also, can you filter strong Alkali solution (NaOH and KOH) through regular paper filter paper or will it "eat it" as H2SO4 does???
Mericad
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Magpie
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I have purchased hydrated lime, Ca(OH)2, by the pound at weed & feed stores. I've also seen it for sale at Ace Hardware.
I purchased 5lbs of KOH off the internet in flake form. It should be more available now with biodiesel in vogue. But if you want to make everything
yourself I understand. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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12AX7
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Classical method is to pile limestone blocks on top of a bed of say, charcoal or coke (I suppose coal would work too, but the volatiles might junk
things up). This is done inside a lime kiln (naturally), which isn't much different from any other cylindrical pile of rock and mortar. The next day
you kick out all the soft blocks of lime and slake it, to much boiling.
Tim
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not_important
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Slaked lime, Ca(OH)2, often labeled "type S lime" in the US, can be found in hardware and construction supply outlets in large bags of 10 to 25 Kg.
It's cheap, and likely easier than making your own CaO.
If you do want to make CaO :
Around a 1000 C will do for making CaO, if you arrange things so that a current of air flows through the heated lime then you can run the conversion
as low as 800 C and perhaps lower, but it will take longer. You're dealing with an equilibrium, CaCO3 <=> CaO + CO2, so removing the CO2 drives
it to the right.
Use steel/iron pipe, copper will oxidise too much.
You will want to concentrate the KOH solution and let it sit in a sealed polyolefin plastic (not glass) bottle for some days, the calcium salts that
were in solution will slowly settle out ; decant the KOH solution from the (hard to filter strong alkali) and toss the last bit of solution and ppt
into the next K2CO3 + Ca(OH)2 reaction you do.
Edit - don't type while cooking...
[Edited on 12-10-2006 by not_important]
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unionised
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limestone + vinegar -> Ca acetate
Ca acetate + drain cleaner-> Ca(OH)2
Ca(OH)2 + K2CO3 -> KOH
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dr. nick
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how is that last step to be done?
got both Ca(OH)2 + K2CO3 and would like to try ...
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12AX7
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Drain cleaner is either NaOH or KOH solution; seems redundant to me...
Tim
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Maja
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Drain cleaner is mostly NaOH prills ... Atleast in my country 
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mericad193724
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Don't get me wrong...I would LOVE to buy some hydrated lime, slaked Lime, or Limestone...its just not available in my area. My hardware store doesn't
sell it (I work there, I would know). My area doesn't have any natural limestone either.
Does Home Depot, Ace, or Lowes (North America Stores) have Ca(OH) or CaO?
The one drain opener I found said "Contains Sodium Hydroxide and Potassium Hydroxide." Another one that only contained KOH was a dark green and low
concentration.
Mericad
[Edited on 13-10-2006 by mericad193724]
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Magpie
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Do you have stores that cater to people with livestock like horses, etc. Check with them. I bought it by the lb for $0.60/lb at a place like that.
I'd be very surprised if they didn't sell hydrated lime in rural NJ.
People who homemake liquid soap should be using KOH. Try to find one of their suppliers.
[Edited on 13-10-2006 by Magpie]
Froogle for potassium hydroxide. You'll find it quickly in 1, 5, and 50 lb quantities.
[Edited on 13-10-2006 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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not_important
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| Quote: | Originally posted by mericad193724
...
Does Home Depot, Ace, or Lowes (North America Stores) have Ca(OH) or CaO?
...
Mericad
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I have been informed that either Home Depot or Lowes, or possibly both, carry slaked lime - again likely to be labeled "type S lime". This was told
to me by someone living on the West Coast, if you are in a heavly urbanised region you may have to get to stores in a more suburban setting.
It appears that for a Kg or less of KOH, going to ebay may be the best deal for people in the US.
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Ephoton
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I have done this before
it was in t old inorganic chem book and I was trying to go compleatly otc.
first I got potasium sulfate which is used for fert.
then I mixed it with calcium hydroxide with extra water.
I heated them for abour an hour then filtered out plaster of
paris adding extra water to wash out potasium hydroxide solution.
the bigest problem I got was distilling the water off of the solution.
best done under vacuum for sure do less damage to your glass
and make a purer product.
pritty easy so easy I dont buy KOH any more.
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Endo
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I recently purchased some lime at the grocery store. Just go to the canning section and look for Pickling Lime. It is cheap <$2 for 2lb.
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denatured
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"People who homemake liquid soap should be using KOH. Try to find one of their suppliers."
I make all the time , I either use KOH or something else they spell it as 'sliKa' or 'silica' I don't know if there is any silicon in it but I'm sure
it is something basic ...
Just a note on potassium hydroxide soln.
I once prepared a very concentrated soln. of it and then I stored it in glass container, after say 16 days I don't remember I found the container
broken and full of white flakes and no soln. when I tried to dissolve these flakes in water, the solubility was very weak if it dissolved at all ...
I'm not sure if it is KOH or something from the air reacted with the soln. it wasn't very air tight ...
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BeerChloride
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alnokta, your KOH had turned into potassium carbonate.
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jimmyboy
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this has already been covered in the sodium hydroxide threads... use the search engine.......
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mericad193724
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I was just thinking...can't you simply produce KOH by the electrolysis of potassium chloride?
KCl is readily available and cheap in huge bags or it is also sold as a salt substitute. I know that under certain conditions electrolysis of KCl will
yield potassium chlorate (hot solution) and IIRC a cold solution will yield potassium hypochlorite(KClO). Under what conditions does KOH form? The Cl
needs to be driven off as Cl2 gas.
Mericad
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The_Davster
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Placing the electrode evolving chloring as near to the surface of the solution as possible will prevent the chlorine from dissolving in the
increasingly basic solution. A cell separated by some sort of membrane or diaphragm may also be of use here.
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Aqua_Fortis_100%
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@ mericad ,
i have this KCl in fertilizer form (pinkish/redish impure powder) and at the momment i playing around purify it..when i dissolved this in boiling
water a weak ammonia smell was observed, and i almost sure which contains NH4Cl what has a similar solubility compared to NaCl (even after
cristalyzing this compound - nice white needles), because i added some NaOH pellets to dried "purified" powder material and a more stronger ammonia
smell was observed.. i think which isn't too good to chlorate manufacture because of changes to form also NH4ClO3 highly dangerous contaminant to
KClO3, maybe making a disappointing synth..
about the KOH:
what about mix stoichometricaly this in diluted sulfuric acid and boil off the HCl gas to make K2SO4 , then add a correct portion of Ca(OH)2 and fiter
off the CaSO4 hydrate, concentrating the solution and recristalyzing the KOH ???
i interested because i have TONS of dilute H2SO4 here..free battery acid solves all problems haha 
[Editado em 27-1-2007 por Aqua_Fortis_100%]
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12AX7
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Wouldn't the NH3 component be eliminated during electrolysis?
Ca(OH)2 works for carbonate or sulfate, sure.
Tim
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womble
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look online for the people that supply the soap makers and the hobbyist essential oil market. The wholesalers will sell you bulk KOH and many other
useful things.
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