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Author: Subject: Route to K2O and Na2O?
halogen
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[*] posted on 16-6-2005 at 06:26
Route to K2O and Na2O?


What of the possibility of Heating KCO3 or NaHCO3 to form K2O or Na2O. At what temprature would this occur and is it feasible (That is is it easier to just buy it?)



F. de Lalande and M. Prud'homme showed that a mixture of boric oxide and sodium chloride is decomposed in a stream of dry air or oxygen at a red heat with the evolution of chlorine.
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[*] posted on 16-6-2005 at 12:52


It would probably just be easier to buy it. To do this with calcium carbonate, as a comparison, requires prolonged and very high temperatures. It might be feasible on a microscale, but nothing larger.
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[*] posted on 16-6-2005 at 15:43


Lot easier to calcine lime or magnesia (just a few hours at yellow heat, easy enough for someone with a pottery kiln) then precipitate the carbonate. I don't know if alkali carbonates will release it at all.

If you want raw oxides, you'll need to dehydrate the material further, I don't know if that happens at any temperature.

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[*] posted on 17-6-2005 at 08:58


It would be incredibly energey intensive to try and preform this conversion. Potassium oxide is incredibly prone to oxidation even from atmospheric oxygen. One possibility would be to mix concentrated KOH with concentrated H<sub>2</sub>O<sub>2</sub> to precipitate potassium peroxide hydrate and heat this in a stream of dry air which would give mostly potassium superoxide and some peroxide then heating this under vacuum to take away the oxygen, under these conditions though oxygen is first lost to leave the peroxide then this decomposes some to potassium metal, some to potassium superoxide and some to potassium oxide.

Note:

Potassium peroxide is oxidized to potassium superoxide by oxygen gas even in liquid ammonia.

The following reaction is prevelent at 450C in vaccum:
2K2O ---> K2O2 + 2K(gas)

[Edited on 6/17/2005 by BromicAcid]




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[*] posted on 17-6-2005 at 09:18


Zinc powder reduces NaOH to Na2O:

2NaOH + Zn --(heat)--> Na2O + ZnO + H2

We did this reaction in school to prove that the product of the reaction of sodium with water was not sodium oxide.
The produced hydrogen was ignited and therefore shown to be contained in the educt.

[Edited on 17-6-2005 by garage chemist]
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[*] posted on 17-6-2005 at 09:32


http://en.wikipedia.org/wiki/Calcination
http://en.wikipedia.org/wiki/Quicklime
http://en.wikipedia.org/wiki/Limekiln

You might be able to do something similar with sodium and potassium carbonates. Although I seem to remember they have a higher decomposition temperature.
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[*] posted on 18-6-2005 at 06:10


Quote:

One possibility would be to mix concentrated KOH with concentrated H2O2 to precipitate potassium peroxide hydrate and heat this in a stream of dry air which would give mostly potassium superoxide and some peroxide then heating this under vacuum to take away the oxygen, under these conditions though oxygen is first lost to leave the peroxide then this decomposes some to potassium metal, some to potassium superoxide and some to potassium oxide.

What concentrations would be suggested?




F. de Lalande and M. Prud'homme showed that a mixture of boric oxide and sodium chloride is decomposed in a stream of dry air or oxygen at a red heat with the evolution of chlorine.
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[*] posted on 18-6-2005 at 10:03


As concentrated as you can muster, remember that the reagents need to be mixed at ~0C due to basified H<sub>2</sub>O<sub>2</sub> being unstable at room temp. The octahydrate of sodium peroxide being formed and the dihydrate of potassium peroxide being formed.



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