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Author: Subject: Help with carbon reduction of cyanate
Terran
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[*] posted on 16-12-2019 at 19:52
Help with carbon reduction of cyanate


So on the sciencemadness wiki I found the preparation for potassium cyanide, but this part confuses me, "One route involves melting cyanuric acid or urea with potassium hydroxide. This gives potassium cyanate. Crush the resulting solid and grind it. Mix it with a reducing agent, such as carbon and heat it until no more gases are released."

I've looked around but I cannot figure out how the carbon works in this reaction, or what it's for.

http://www.sciencemadness.org/smwiki/index.php/Potassium_cya...




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j_sum1
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[*] posted on 16-12-2019 at 20:48


KCN is similar to NaCN in synthesis and use.
The page you cited links to the page for NaCN.
http://www.sciencemadness.org/smwiki/index.php/Sodium_cyanid...
This has the answer to your question and a notable warning.
I would be hesitant about making cyanides myself and would not recommend it to anyone without a lot of experience and knowledge. The fact that you are asking about a process as straightforward as carbon reduction raises warning flags. Just don't do it.
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Terran
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[*] posted on 17-12-2019 at 06:33


Thank you, I'm not planning to make any quite yet, I just have never come across carbon reduction before.



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XeonTheMGPony
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[*] posted on 18-12-2019 at 04:10


Quote: Originally posted by Terran  
Thank you, I'm not planning to make any quite yet, I just have never come across carbon reduction before.


It is used as a fuel in a great many reductions it is mainly used in metal industry. Most classical is gun powder

Learn it as it is vital for a great deal of things
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Tsjerk
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[*] posted on 18-12-2019 at 06:49


Quote: Originally posted by XeonTheMGPony  
Quote: Originally posted by Terran  
Thank you, I'm not planning to make any quite yet, I just have never come across carbon reduction before.


It is used as a fuel in a great many reductions it is mainly used in metal industry. Most classical is gun powder

Learn it as it is vital for a great deal of things


I would call the production of iron the most classic ;) about 3200 years old.
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PirateDocBrown
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[*] posted on 18-12-2019 at 08:10


Much easier to make KCN from laundry bluing.

Heat the bluing gently, to drive off the water.
When it's dry, it's essentially Fe7(CN)18.
Add KOH, and raise the temp to a melt.
Hold, excluding air, for a couple of hours for the reaction to finish.
Dissolve in anhydrous EtOH. Neither unreacted Prussian Blue nor iron oxides/hydroxides are soluble in it, but KCN is.
Separate from unreacted KOH via recrystallization.

All OTC, lower temps, nothing in (insanely toxic) gas phase, easy separation.

https://www.amazon.com/Mrs-Stewarts-Bluing-1101-MPLS-8oz/dp/...

[Edited on 12/18/19 by PirateDocBrown]




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Tsjerk
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[*] posted on 18-12-2019 at 09:21


Quote: Originally posted by PirateDocBrown  

Separate from unreacted KOH via recrystallization.
[Edited on 12/18/19 by PirateDocBrown]


How do you suggest doing the recrystallization?
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Dan Vizine
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[*] posted on 18-12-2019 at 10:52


The KOH/KCN separation is sure not going to be a walk in the park. It probably has a definite learning curve.

I think it's a matter of first extracting the pulverized reaction mass with boiling, fairly anhydrous EtOH. You then clarify by filtration and concentrate the solution to incipient crystallization. Just getting sufficiently dry alcohol might be quite difficult.

On the other hand, this is the same exact type of horrible separation that the cyanate route suffers from it its final stages. Just horrible.

I'd go by the pyrolytic route. The cyanate route is really just an industrial process that is ill-suited for home synthesis.


[Edited on 12/19/2019 by Dan Vizine]





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[*] posted on 18-12-2019 at 20:57


Quote: Originally posted by Tsjerk  
Quote: Originally posted by PirateDocBrown  

Separate from unreacted KOH via recrystallization.
[Edited on 12/18/19 by PirateDocBrown]


How do you suggest doing the recrystallization?


KOH is far more soluble in cold EtOH than KCN.

Dissolve the mix in a minimum of boiling EtOH, then chill.

The crystals formed will be much purer than you started, assuming you have excluded atmospheric contamination (Basically, O2 to react to KOCN, and CO2 to react KOH to KHCO3).

I'd do the recrystallization at least twice.




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[*] posted on 19-12-2019 at 06:13


We tried the cyanate reduction (it's in one of the videos) and the results were pretty terrible. You can determine via a prussian blue test that there is cyanide in the product, but a low uncertain concentration.

Ultimately the only method we tried that produced cyanide salts pure enough for synthetic purposes (e.g. to prepare mandelic or malonic acid) was the reaction of anhydrous potassium ferrocyanide powder with sodium metal.




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