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Zyklon-A
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I don't see propylene carbonate mentioned in the last few pages of this thread. Did you mean to post in this one?
[EDIT] it's not used as a solvent, but rather a non-reactive electrolytic solution, used to plate out metals that would otherwise react with common
solutions, like water.
[Edited on 25-11-2014 by Zyklon-A]
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gdflp
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No, I meant as a replacement for tetralin in the magnesium, tertiary alcohol cat. method. If it can be used for electrolysis it obviously isn't
reactive towards potassium, it has a high boiling point at 242°C to allow the reaction to reflux, are there any other things I'm missing which will
cause it to not work in that method.
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blogfast25
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Quote: Originally posted by gdflp  | | No, I meant as a replacement for tetralin in the magnesium, tertiary alcohol cat. method. If it can be used for electrolysis it obviously isn't
reactive towards potassium, it has a high boiling point at 242°C to allow the reaction to reflux, are there any other things I'm missing which will
cause it to not work in that method. |
It would be worth trying that but I have concerns about its reactivity towards KOH and the alcohol catalyst at these temperatures. Also Mg will have a
tendency to snatch the abundant oxygen.
This resource gives some indications on the chemical resistance of polypropylene carbonate to various chemicals:
http://www.engineeringtoolbox.com/polypropylene-pp-chemical-...
But 200 C is a long way off 60 C!
[Edited on 30-11-2014 by blogfast25]
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Metacelsus
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Yes, it's an ester, which means that it is probably unstable in the presence of KOH (saponification will take place).
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Zyklon-A
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blogfast25, I'm confused by your link. You say it's for polypropylene carbonate, but the link is for polypropylene, a hydrocarbon
thermoplastic polymer, containing no oxygen (hence hydrocarbon).
Is there something I'm missing?
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blogfast25
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Yes, it's not for propylene carbonate. My bad.
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gdflp
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No, we're talking about the solvent for the reaction. If t-Butanol was used, the reaction temperature would remain at the boiling point of t-Butanol,
82°C. The reaction needs to be around 200°C for the required intermediates to form. t-Butanol is used in the patent, but it is used as a catalyst
rather than a solvent.
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blogfast25
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More t-butanol than KOH would simply result in all K being present as K t-butanoate. Period.
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S.C. Wack
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No point arguing with Spammer With New Tricks tibow64.
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blogfast25
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Sorry, didn't realise he was a spammer.
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maleic
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It's really cool! And the commentary also great!
I hope this is true and feasible.
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Blunotte
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Hello, nobody tried this?
K2C4H4O6 --Heat--> K2CO3 + 2C + CO (^gas) + 2H2O (^gas) --Heat800°--> 2K (^gas) + 3 CO (^gas)
The potassium can be condensed in a metal tube in absence of air, and CO and H2O will escape as gas
[Edited on 3-4-2015 by Blunotte]
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blogfast25
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| Quote: Originally posted by Blunotte | Hello, nobody tried this?
K2C4H4O6 --Heat--> K2CO3 + 2C + CO (^gas) + 2H2O (^gas) --Heat800°--> 2K (^gas) + 3 CO (^gas)
The potassium can be condensed in a metal tube in absence of air, and CO and H2O will escape as gas
[Edited on 3-4-2015 by Blunotte] |
What's "K2C4H4O6"?
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Blunotte
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Potassium tartrate (LINK to Wiki)
At about 400 ° C decomposes, and the result of the decomposition is in the correct stoichiometric ratio for the subsequent reaction, in addition to
achieving the reagents perfectly mixed.
Both reactions should be carried out in a metal tube, closed at one end, and the other must be crushed so as to leave only a small flat opening.
The carbon monoxide burns in air, and the metallic potassium falls into a container filled with liquid paraffin.
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Blunotte
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procedure:
Take an iron tube of about 50 cm in length and 2 cm in diameter, close to one end, and the other end is crushed in a vice, to leave a small output.
Pour in the tube a few grams of potassium tartrate.
Place the tube horizontally above a barbecue switched on, with a beaker of paraffin oil under the exit.
Wait a little.
All Done.
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j_sum1
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@ Blunotte
Try it and see. Report back. To my relatively untrained eye it seems vaguely like it might be feasible. It is a lot higher temperature than the
process discussed here -- which, incidentally I attempted unsuccessfully. (I ill attempt again with cleaner, finer magnesium and a better grade of
mineral oil.)
Higher temperature and gaseous metals seems like a combination that is likely to introduce unforeseen problems, but it might work.
Have you checked out the feasibility from a thermodynamic viewpoint?
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Blunotte
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@j_sum1
Many years ago, the potassium was prepared in this manner, at the industrial level.
I'm sure it works well.
What I don't know is if we can repeat the experiment in small, and make it in a home lab 
My son is growing up, and I want to prepare a small home lab, so I do not know if we can do this experiment now, I think we need some time 
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blogfast25
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| Quote: Originally posted by Blunotte | procedure:
Take an iron tube of about 50 cm in length and 2 cm in diameter, close to one end, and the other end is crushed in a vice, to leave a small output.
Pour in the tube a few grams of potassium tartrate.
Place the tube horizontally above a barbecue switched on, with a beaker of paraffin oil under the exit.
Wait a little.
All Done. |
I’m sorry but this is complete nonsense. On strong heating potassium tartrate in all likelihood decomposes to potassium carbonate. The pyrolysis of
potassium bitartrate to potassium carbonate (‘Pearl Ash’, if it came from ‘cream of tartar’) was once an industrial
preparation of the latter. At very high temperature K2CO3 will partially decompose to K2O but not to elemental potassium.
No potassium without a reducing agent or electrolysis.
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Blunotte
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| Quote: Originally posted by blogfast25 | I’m sorry but this is complete nonsense. On strong heating potassium tartrate in all likelihood decomposes to potassium carbonate. The pyrolysis of
potassium bitartrate to potassium carbonate (‘Pearl Ash’, if it came from ‘cream of tartar’) was once an industrial
preparation of the latter. At very high temperature K2CO3 will partially decompose to K2O but not to elemental potassium.
No potassium without a reducing agent or electrolysis. |
Please read what I wrote before:
K2C4H4O6 --Heat--> K2CO3 + 2C + CO (^gas) + 2H2O (^gas) --Heat800°--> 2K (^gas) + 3 CO (^gas)
At first time, CO and H2O will be produced and escapes as gas.
In a second time, K2CO3 + 2C -> 2K + 3CO
Potassium carbonate + carbon --StrongHeat--> Carbon monoxide (escape as gas) + metallic potassium as vapor.
Potassium condensate as liquid in the tube and fall in a cup with liquid paraffine.
Stop
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blogfast25
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Blunotte:
If you have some credible references to that process, I'd like to see them. Until then, I remain sceptical. At the very least it would require vacuum,
as in the case of the carbothermic reduction of magnesia.
This below does reference a process for carbothermic reduction of soda and potash:
| Quote: | | The rst recognized production of sodium and potassium metalswas by Sir Humphrey Davey. In November 1807, Davey announced the discovery of sodium and
potassium metals which he had been able to produce by electrolysis of potassium or sodium salts. Shortly after Daveys announcement, Gay-Lussac and
Thenard announced to the Institute of Science in Paris that they had decomposed potash and soda by treating them with iron at a high temperature. A
few weeks later, in the spring of i808, Curaudau told the Institute of Science that he had succeeded in metallizing potash and sodium by strongly
heating them with charcoal. The Curaudau process was further developed by Deville in France into a commercial process and for a large number of years
was the principal `source of sodium metal. Devilles method produced all the sodium that was needed for the production of aluminum (which was the
principal market for sodium) until the sodium industry was upset by the introduction of the Hall electrolytic process for the preparation of aluminum
in the last ten years of the 19th century. |
http://www.google.co.uk/patents/US2930689
[Edited on 8-4-2015 by blogfast25]
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Polverone
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There is a good description of the process here: https://archive.org/stream/ldpd_10922488_002#page/746/mode/2...
The process was tedious, low-yielding, hard on equipment, energy intensive, and hazardous. But it was practiced industrially for decades.
PGP Key and corresponding e-mail address
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blogfast25
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Thank you, Polverone. I managed to find some information earlier on tonight but it's amazing how many processes seem to get 'forgotten' when they get
into disuse. Most modern sources don't mention this historical process anymore.
This JSTOR page provides some description too:
http://archive.org/stream/jstor-30073580/30073580_djvu.txt
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Blunotte
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Thank you, Polverone.
I hate when people do not believe me 
About 25 or 30 years ago, I had a book where the preparation was accurately described, and there were also some images.
Now unfortunately I can not find this book, and I can not prove anything.
But in your library, there is still a book in which he speaks of this preparation:
A Text-Book of Inorganic Chemistry Volume II: The Alkali-Metals and Their Congeners (A. Jamieson Walker, edited by J. Newton Friend), page 152.
(just few rows, but...)
I know, the preparation has a low yield, is not elegant, it needs high temperatures...
But it has very low costs: the potassium tartrate (or its acid tartrate) is cheap (here in Europe we use it for stabilization of wines, only few euro
for a kilo), and you do not need expensive equipment, just an iron pipe and a brazier with coal 
Ok, it's enough, I seem to fight the windmills, if someone wants to try, well. For me, I'll try to do the preparation when my son will be older (he is
only 7 years old, now)
Have a nice day
[Edited on 9-4-2015 by Blunotte]
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blogfast25
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| Quote: Originally posted by Blunotte | I hate when people do not believe me
About 25 or 30 years ago, I had a book where the preparation was accurately described, and there were also some images.
Now unfortunately I can not find this book, and I can not prove anything.
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Scepticism is part of science. No need to get mad about that. 
Polverone's reference puts the matter to rest. It also mentions potassium tartrate (Argol) as a source of potash/carbon for carbothermic reduction of
potassium metal.
But read the relevant section of that ebook: the method is hardly as easy as you describe it. One reported yield was only about 50 %. Modern
adaptations, perhaps using argon flux, could possibly improve it a lot and make it safer. I'll put it on my 'bucket list'.
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APO
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It looks like the original thread for potassium production on versuchschemie doesn't exist anymore!?!
"Damn it George! I told you not to drop me!"
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