extraction of K out of KNO3?

[iron raven]

hello,
as i flicked through one of my chemistry books, i noticed a page on electrolyses. They were talking about electrolyses of Compounds such as NaCl. They stated that if an electrical current passed through a compound could break it up. If this is true, which i think is, by placing KNO3 into a metal container or a glass container and heating it up and then passing an elctrical current through it one could gain pottasium out of it. Becouse the products will be gasses one should be left with near pure pottasium. the reaction that would occur would be as follows.

2 KNO3 + thermal energy + electrolyses --> 2 K + N2 + 3 02

I added thermal energy to the eqaution becouse i thought that KNO3 in its crystal structure would not conduct electricity. would it conduct electrcity in its liqiud state? What material should i make my electrodes out of? any thing would be of help
thank you all
iron raven

[scarletmanuka]

Forget it!
You are probably better of using something like KCl instead, because the electrolysis would be simpler, but you are talking about a very high melting point (Electrolysis of fused(molten) NaCl to give Na has added CaCl2 to lower the melting point, i don't know if this would work for KCl). Molten sodium is a very good solvent for lighter metals and potassium would probably have the same effect, so you could not use a normalmetal container or glass which would break at such high temperatures.
The other problem is extracting the molten potassium which would oxidise straight away on exposure to air. I don't think i am allowed to post pictures, so have a look on a search engine for a diagram of a sodium cell, pretty tricky.

[vulture]

Electrolysing KNO3 is first of all waste of a chemical to could be made much more useful and secondly it won't work, only the nitrate will be reduced.

Sodium cells aren't very tricky, I don't know what you mean by that.

Glass wouldn't necessarily break, but it would be severely attacked by the molten alkali salts and the metal itself.

[megalomania]

On a lark I attempted this a few days ago with less than successful results. I obtained a new high temperature furnace and I wanted to test the thing out. I wanted to try electrolyzing a mixture of sodium, potassium, calcium, and magnesium chloride (Wal-Mart ice melting salt), so I added a sample to a crucible.

Unfortunately my crucible cracked and the salt vaporized before I had a chance to zap it, and of course I could not get my battery charger to work as the contacts are quite corroded (too much chlorate production recently has eaten away much of the alligator clips). I did prove my furnace can reach the necessary temperature as I found some melted salt residue in what remained of my crucible.

I have seen credible reports of experiments like this being done, and I have read the industrial literature about it, so it does indeed work. Of course on the improvised scale there is little hope for large scale production, or purity. For the future I have invested in sturdy steel pipe caps; steel crucibles make the best receptacles for this kind of work. I have done this before in a furnace at work, I melted pure sodium chloride in a steel crucible. I had no electrodes to zap it then.

I have observed the potential for molten metals to ignite under such improvised conditions, an unfortunate consequence. With respect to this problem I am designing a way to make magnesium metal. This will require an inert atmosphere, or rather a means of excluding oxygen, as magnesium is quite flammable at high temperatures. I hope to be able to heat a small capped pipe, which will act as my crucible. The top will be secured with some cement, into the center of which will be a carbon electrode. With this setup I can use the metal pipe as one electrode and the carbon as the other without creating a short circuit and without requiring me drilling a hole into a half inch of solid steel (a pipe cap). A simple vent tube of copper tubing led to a water trap will exclude air and allow such nasties as chlorine to harmlessly pass away. Now all I need is a heat source strong enough to melt magnesium chloride.

[megalomania]

I found a thread in the archives on this very same topic, since we already have this thread going, I will stick it here...


kingspaz
Frequent Poster
Posts: 347
From: UK
Registered: SEP 2000
posted 05-11-2001 05:50 PM
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I have searched for this topic because I was sure there has already been something about this but I couldn't find it. In this topic i remember i suggested electrolising KCl, to get pure metallic potassium, which is difficult because of the high melting point of KCl. I don't know why I haven't thought of this before but why not electrolise KNO3 because it has a low melting point and so should be easy to electrolise. I think i'll try this in a week or so if I get round to it.
Has anybody tried this or anything similar?


FadeToBlackened
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Posts: 201
From: Hell
Registered: MAR 2001
posted 05-11-2001 05:57 PM
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I made a post about it awhile back (you have to look back a few months) but KOH would probably be better than KCl, and KNO3, well, i dont know it might decompose or something i dont know.


Agent Blak
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Posts: 766
From: Sk. Canada
Registered: SEP 2000
posted 05-11-2001 08:17 PM
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If you heat it up hot enough could you not drive off the HydrOxide(OH) Ion? Although it may have a strong bond and this would be unfeasible, just a thought though.
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nbk2000
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Posts: 1096
From: Guess
Registered: SEP 2000
posted 05-12-2001 10:41 AM
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If you used a mercury electrode it would combine with the hydroxide radical to form a mercury oxide salt and free hydrogenl. This is what's Davies used for discovering the pure element in the first place.
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Nitro
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posted 05-12-2001 03:35 PM
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Yep agent black it can be made without elektrolysing.I ve read in an old bock they made it around 1890 out an mixture of sodium carbonate, chalk, charcoal they glow it in an iron retort the sodium distill off and they lit the vapors in petrol.and an other methode was reducing Sodium hydrate with iron carbide.I think both methodes works for potassium too.


kingspaz
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Posts: 347
From: UK
Registered: SEP 2000
posted 05-12-2001 04:55 PM
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thanks for the replies guys


Alchemist
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Posts: 211
From: Woodland hills,Ca.,L.A.
Registered: NOV 2000
posted 05-13-2001 11:56 AM
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Hello gang,
I have seen the one Nitro posted also in old chem books at the library, the one from 1890.
If anyone trys this please let us know how it works out. Quanities and etc.

P.S., I'll look again for that book and try to scan it!

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Agent Blak
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Posts: 766
From: Sk. Canada
Registered: SEP 2000
posted 05-13-2001 01:07 PM
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Nitro,
My name is Agent Blak... not Agent Black.
I don't know if it is possible to do it that way or not. I read in a experiment book in a school library that something called pyrophoric(Sp?) Lead could be made by heating up Lead Nitrate(Pb{NO3}2 I think). It said that it stripped all of the ions off the Lead and, you were left with lead in a highly energized state. I thought it could be a possiblity in this case also.

------------------
A wise man once said:
"...There Will Be No
Stand Off At High Noon
... Shoot'em In The Back
And, Shoot'em In The Dark"

Agent Blak-------OUT!!

[This message has been edited by Agent Blak (edited May 13, 2001).]



CodeMason
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Posts: 383
From: Your Nightmares
Registered: NOV 2000
posted 05-13-2001 06:25 PM
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'Pyrophoric lead' refers to elemental lead that will ignite spontaneously in the air. This is because it's so energized, it will oxidize so fast that it will cause combustion.