Zyklon-A
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New method for potassium?
I know such topics have been flogged to death, but here is a new method that I thought of when reading this, "Potassium oxide can be made to decompose around 350-400C. Under an ultrahigh vacuum it forms potassium peroxide and potassium metal at this
temperature.''
What I'm thinking is, make this vacuum pump, (I was going to make this anyway), put K2O in an airtight heat resistant container, apply vacuum, heat to 350-400C wait 5-10
minutes, and the reaction should be done.
To separate the mixture, I was thinking, dissolve in liquid NH4, then separate the NH4 with K, distill the NH4 off, and you have K!
Some thoughts:
The NH4 part may be unnecessary, dissolving an alkali metal in NH4 is just something I've wanted to do for a while.
It may not work at all, as I have never tested the decomp. of K2O.
The potassium might boil at that temp, with vacuum.
[Edited on 11-1-2014 by Zyklonb]
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WGTR
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There is a topic on this here that may be of use.
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Zyklon-A
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Thanks, very informative... but they did not say anything about it under 100% vacuum, I suspect that nothing would happen, now. I think I might still
try it though, as soon as I can build that vacuum pump.
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BromicAcid
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Please... it hurts to read terms like "ultra-high vacuum" and "100% vacuum" when you have no clue what real vacuum is. If you did you wouldn't have
linked to a hand pumped vacuum chamber on youtube. A pump that pulls 1 mm Hg is a good pump, a pump that gets 0.1 or 0.001 mm Hg is a really good
pump. Getting even lower, now you're talking diffusion pumps. The reference that WGTR provided actually has the information you're interested in,
quoted in fact by me from an actual literature source <gasp>
| Quote: | ...for example, [potassium peroxide] can be produced by heating potassium oxide, K2O, in a vacuum (10^-5 mm Hg) at temperatures above 450°C, i.e.,
2K2O (Solid) -----> K2O2 (Solid) + 2K (gas) |
From the loveable Peroxides, Superoxides, and Ozonides of Alkali and Alkaline Earth Metals by Il'ya Ivanovich Vol'nov - Plenum Press 1966
To me this does not seem to be preparative method, it is instead a curiosity. The vacuum employed is painful if not next to impossible to achieve at
home, you will not (and you can quote me on this) be able to achieve 0.00001 mm Hg using a hand pump. And this reaction will not be complete in "5-10
minutes". And as for extracting your product with NH4... no... not even going to go there.
Your heart is in the right place, but look at this one step at a time. You're biting off more than you can chew.
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BromicAcid
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Addendum:
The aforementioned reference from Vol'Nov's book is referenced itself to the following source:
162. W. Klemm and J. J. Scharf. Z. Anorg. Allgem. Chem. 303:263 (1960).
Thankfully I just happened to have the book in my library. It would be interesting to see the original reference where this all started since I
gather from the information presented that this is all third hand with the Peroxides book as the intermediate.
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bfesser
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Thread Moved
11-1-2014 at 04:51 |
bfesser
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[moved from Technochemistry]
NH<sub>4</sub><sup>+</sup> is the <a href="http://en.wikipedia.org/wiki/Ammonium" target="_blank">ammonium
cation</a> <img src="../scipics/_wiki.png" />. NH<sub>3</sub> is <a href="http://en.wikipedia.org/wiki/Ammonia"
target="_blank">ammonia</a> <img src="../scipics/_wiki.png" />, a gas—something you won't be working with at home.
NH<sub>3</sub>(aq)</a> is <a href="http://en.wikipedia.org/wiki/Ammonium_hydroxide" target="_blank">household
ammonia</a> <img src="../scipics/_wiki.png" />, or ammonium hydroxide (NH<sub>4</sub>OH), is the one you're likely familiar
with—and quite useless for this purpose.
As has been pointed out, the hand vacuum pump is hopeless for this purpose. I highly doubt you'd be able to get away with anything less than a <a
href="http://en.wikipedia.org/wiki/Diffusion_pump" target="_blank">diffusion pump</a> <img src="../scipics/_wiki.png" />. Finally, it
might help your understanding to read up on <a href="http://en.wikipedia.org/wiki/Vacuum" target="_blank">vacuum</a> <img
src="../scipics/_wiki.png" />. We're not trying to discourage you from pursuing amateur chemistry, but please take heed when we tell you that this
is far beyond your means at this time.
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Zyklon-A
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You guys are all right about the vacuum... I have had zero chance to work with any kind of vacuum whatsoever, I'm only 15 and haven't even had a high
school chemistry class yet, (although I have read and understood more than 10 books on the subject.)
I do know the difference between household ammonia and liquid ammonia, and have worked with liquid ammonia once before.
About putting it in the wrong forum, I just saw the topics in the Technochemistry forum:
hot electrochemical sodium,
unconventional sodium,
Homebuilt 1300°C tube furnace,
Birkeland-Eyde reactor for making nitric acid, ect. it just looked like the right place.
Anyway, it was just a thought...
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Zyklon-A
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Back to the question, could SWIM make potassium if he/she had a pump powerful enough? I've given up, but I just want to know if it's possible.
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elementcollector1
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Please don't use that particular acronym. We all know who you're referring to and just how much he "isn't" you.
I'll give the standard answer:
Theoretically, yes.
Practically, absolutely not.
Read the potassium thread, and then read up on propylene carbonate - these are two methods that are viable for amateurs.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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bfesser
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Thread Pruned
14-1-2014 at 14:59 |
vmelkon
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Quote: Originally posted by Zyklonb  | | Back to the question, could SWIM make potassium if he/she had a pump powerful enough? I've given up, but I just want to know if it's possible.
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I didn't find anything about it on the web or in my chem dictionary.
But what is the assumption here? Are you thinking that it decomposes to its elements on heating? I doubt it.
Then there is the problem of having K2O. There is no method besides combining the elements or KNO3 + K and perhaps other means that involve K as well.
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Zyklon-A
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| Quote: Originally posted by Zyklonb | | Back to the question, could SWIM make potassium if he/she had a pump powerful enough? I've given up, but I just want to know if it's possible.
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I don't see what's wrong with SWIM, it's basically a joke, and in this case, I'm clearly NOT going to try it, because I don't have a vacuum pump.
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BromicAcid
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| Quote: Originally posted by vmelkon | | Then there is the problem of having K2O. There is no method besides combining the elements or KNO3 + K and perhaps other means that involve K as well.
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I know that's what the Wiki says but something about that turns me off. Traditionally as far as I know potassium oxide was prepared by bubbling
oxygen through a solution of potassium metal in liquid ammonia. The amount of oxygen has to be calculated as you can still oxidize to the peroxide
even under those conditions. And as for the preparation of potassium oxide without potassium metal, I was once interested in this method of
preparation too but could not find a good way to get to potassium oxide without potassium metal, interestingly enough though you can get to the
peroxide without potassium metal but that does no good in this situation:
| Quote: | | The K<sub>2</sub>O<sub>2</sub> *2H2O2 compound is known and is formed by the reaction of KOH with a
concentrated solution of hydrogen peroxide. Upon decomposition, it is converted to KO2. |
Ref: G. L. Cunningham and F. R. Romesberg. U.S. Patent 2908552 (1959
Ref: L. A. Kazarnovskii and A. B. Neiding. Doki. Akad. Nauk SSSR 86:717 (1952)
Ref: A. W. Petrocelli and D. L. Kraus. J. Chem. Educ. 40:146 (1963)
It would be beautiful in a way, prepare potassium metal using only oxidizing agents. Convert the hydroxide to the peroxide perhydrate then decompose
to the peroxide but getting it from the potassium peroxide to potassium oxide... that's much harder than one would expect.
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woelen
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Zyklonb, I love to read your enthusiastic ideas. Thirty years or so ago, I also was pondering all kinds of curious reactions to make special
chemicals. But now I know that the majority of all those very special reactions only are lab curiousities which may be important from a theoretical
point of view, but have no practical synthetic value. This kind of reactions is interesting, because they can tell us something about the properties
of certain elements and give us theoretical insight. But do not think that the person who has done this experiment after his experiment had a lump of
K-metal. He most likely started with a few grams of K2O, put this in a hot vacuum chamber and allowed his vacuum pump to make the required vacuum over
a period of hours or even days, using multitonne equipment and thousands of kWh of electrical energy. After that, he probably was capable using
spectroscopic or some other advanced means to show that in the vacuum chamber there was an atmosphere of K-gas at a pressure of a few millionth of an
atmosphere.
Under very special situations many weird chemical reactions can occur. I once read about someone making NO3 in a chamber at -80 C or so, at low
pressure, containing NO+NO2 vapor at very low pressure and applying a silent discharge in this gas for a few days and after that, some traces of a
weird compound appear, which seems to be NO3 and which decomposes immediately when the temperature rises above -80 C or so or when the pressure rises
above 0.001 atmosphere. It is this kind of extreme reactions which is done in quite a few labs, not for the sake of finding a method for making new
compounds, but for the sake of getting better understanding of the chemistry of the elements. Knowledge from this kind of research then may e.g. be
applied in atmosphere science to elucidate mechanisms for ozone depletion, get a better understaning of how certain human-made waste compounds are
broken down and how fast they are broken down, or this knowledge may be applied in astronomy to understand how certain molecules can be formed in
distant nebulae or in atmospheres of certain planets, etc. etc.
If you want nice results at your home, then I would start with more easy to make compounds. E.g. CuCl2.2H2O from copper, hydrochloric acid and
hydrogen peroxide, KClO3 from KCl, KBrO3 from KBr, and that kind of more mundane things. There is enough info on this kind of reactions on
sciencemadness and it may give a lot of fun and understanding and experience if you actually succesfully made and isolated such relatively easy to
make compounds. Also be prepared that even for such compounds, you need quite a lot of time and also some investment of equipment, although the latter
certainly is within reach of you (think of a few tens of euros or dollars).
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