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Author: Subject: Preparation of cyanides
Myfanwy
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[*] posted on 9-2-2010 at 06:50


no. much hydrogen cyanide will just gas out and does not react.

anyway my vid was deleted on youtube.
maybe i will reupload it.




[Edited on 9-2-2010 by Myfanwy]




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vassili78
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[*] posted on 9-2-2010 at 12:18


try metacafe.com to upload your videos. it is less controled that youtube, you can find lot of chemistry videos or other thing like that.

your video was very nice. if i liquify completely the HCN, the yield will be better?

i tried today with no good results, i will try to cool it with the same system you used but instead of a baker containing NaOH solution, i will put an empty baker surrounded with water, salt and ice to be sure that the HCN will be liquid and then i will put it into a solution of NaOH.

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[*] posted on 9-2-2010 at 13:04


Quote: Originally posted by vassili78  
i will put an empty baker surrounded with water, salt and ice to be sure that the HCN will be liquid and then i will put it into a solution of NaOH.

It is not like I will shed a tear if there will be one less kewl on this world, but still I take it as my duty to ask you if you have enough intelligence to imagine what happens if you pour liquid HCN into a caustic solution?

How about reading some chemistry books first?
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Myfanwy
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[*] posted on 9-2-2010 at 13:16


what would happen if you pour all the HCN into the lye? Such an exothermic reaction, that all the HCN just gas out again?



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vassili78
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[*] posted on 10-2-2010 at 11:45


i think the HCN will polymerize with a violent reaction...
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vassili78
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[*] posted on 10-2-2010 at 11:53


that's what happen to MARIO840, his solution turn to yellow but he didnt' describes any violent reaction. may be i'm wrong...
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KnooBill
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[*] posted on 12-2-2010 at 13:47


Your solution turning yellow is probably due to polymerization of the triple bond between the carbon and nitrogen. I did not neutralize HCN with ethanol and KOH immediately but did it after the ferrocyanide finished reacting with H2SO4. It was kept in an ice bath instead with an one way valve to keep the pressures equal (HCN takes volume in the bottle hence air must go out). However you need explerience to practise the experiment, and youtube is no chemistry tutor.
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evil_lurker
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[*] posted on 7-3-2010 at 11:07


Here lately it has occurred to me that rather than simply attempting to bubble HCN thru a base and try and isolate pure cyanide salts it should be possible to instead utilize commonly found weak base anion exchange resins which adsorb and form complexes with HCN.

If that is the case, then HCN can be safely sequesterd onto the surface of the polymer, and NaCN could easily be eluted in stoichemetric amounts simply by subjecting the resin to a solution of NaOH.

Will definately have to do more research into which resin would produce the best results.





Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.
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Picric-A
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[*] posted on 7-3-2010 at 12:19


Quote: Originally posted by evil_lurker  
Here lately it has occurred to me that rather than simply attempting to bubble HCN thru a base and try and isolate pure cyanide salts it should be possible to instead utilize commonly found weak base anion exchange resins which adsorb and form complexes with HCN.

If that is the case, then HCN can be safely sequesterd onto the surface of the polymer, and NaCN could easily be eluted in stoichemetric amounts simply by subjecting the resin to a solution of NaOH.

Will definately have to do more research into which resin would produce the best results.



One problem with this is it would be difficult to recover 100% of the cyanide from the resin and this would leave you with a highly toxic resin to dispose of.
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Taoiseach
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[*] posted on 7-4-2010 at 22:01


I recently mixed together potassium ferricyanide (or was it ferro - well the yellow stuff anyways) with ammonium chloride and heated small amounts. There was a strong smell of HCN and the mixture turned a nice blue color.

I have not yet dared try to distill ammonium cyanide from a larger amount but it looks to be possible. Ammonium cyanide is less volatile than HCN (altough still volatile enough to kill you with its vapours!) and reacts with ethanolic KOH solution to form KCN. The latter should precipate immediately due to its insolubility in EtOH.
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[*] posted on 8-4-2010 at 04:56


Nice work Taoiseach, what kind of temperature did you heat them to? I didn't realise Ammonium cyanide was that volatile, wikipedia says bp of 36C, which is about the same as Ether. Heavy cooling will be required for distillation, but it's still a nicer material to distil than HCN. Good find!

Not sure about heavy cooling... it appears ammonium cyanide is a solid, and it would clog the condenser... any idea as to the mp of NH4CN?

[Edited on 8-4-2010 by DJF90]
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Taoiseach
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[*] posted on 9-4-2010 at 07:47


I didnt control temperature. Literature says it can be destilled from the mixture at 100°C. Also that it is very soluble in ethanol. I would try to catch it in ice-cold ethanol.

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Sydenhams chorea
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[*] posted on 16-5-2010 at 04:54


According to his youtube page (http://www.youtube.com/user/Myfanwy94) the user known as "Myfanwy" has recently passed away at the age of 16. I can only hope this was not the result of his recent experiments with cyanides.

Quote:

just2diy (2 weken geleden)
I miss him, he has always loved the chemistry and now they killed him.
I was in the same class as he saw and now I teach every day the place. I'm so sorry about him.

In memory of:
Myfanwy94 (Max Klempke)
04/19/2010





Il n'y a point de sots si incommodes que ceux qui ont de l'esprit.
François de La Rochefoucauld.
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Taoiseach
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[*] posted on 17-5-2010 at 09:11


I recently tried the C reduction of potassium cyanate, made by fusing K2CO3 with urea. The fused mass, after cooling, was extracted with warm water (30°C). After adding EtOH and cooling in a freezer, a few crystals of KCN precipated but the yield was neglible. The solution supersaturated and only started to crystallize after vigorous shaking. The stench of HCN was barely tolerable; I was really suprised how pungent and penetrating it smells. Even the next day the smell was clearly noticable in my home lab.

Lessons learned: The entire procedure has to be done outside or under a good fume hood. CO2 from the air liberates a lot of HCN from the solution - enough to give a numb and weird feeling in the throat. You can only smell the first wiff as it numbs the sense of smell, then after a while at fresh air you can smell it again :) Hot water has to be used for extraction - this however causes hydrolysis of the cyanide. Idea: Filtrate the hot extract into a cooled flask filled with ice-cold EtOH. The reaction vessel must be free of rust or ferrocyanide will be formed, evidenced by a distinct yellow coloration of the filtrate.

Any other ideas of how to extract KCN from the melt?
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[*] posted on 17-5-2010 at 11:30


You should have got more than a few crystals unless the reduction was very incomplete or you didn't use enough alcohol. Freezer cooling is not necessary. There should be an obvious precipitation (not visibly crystalline) after just a few seconds when the leach solution is poured into ethanol and stirred.

I have found that reduction can be visible monitored by evolution of gas bubbles during the heating process, after the full mass has melted. I believe the bubbles are CO because they will burn as they pop if the surface of the melt is exposed to air.

I used charcoal or propane heat to do the reductions. It can be a while before the evolution of bubbles slows down. Higher heat makes the reaction go much faster. If the melt has free access to air the re-oxidation of cyanide to cyanate may prevent realization of a high cyanide content product.

I will admit that of my few dozen trials and production runs that I ever made while experimenting with this method I only made a few with potassium compounds instead of sodium, and those before I had much experience optimizing conditions. Still, I would be rather surprised if the choice of cation made a dramatic difference.




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Taoiseach
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[*] posted on 17-5-2010 at 21:31


Thx for the answer Polverone. How much water/EtOH did you use and what temperature? I calculated the theoretical yield of cyanide and the amount of 30°C water needed to dissolve it, then doubled the volume. An equal volume of EtOH was used.

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[*] posted on 18-5-2010 at 08:58


The water was at "room temperature" -- I actually didn't take its temperature. The quantity of water you're using sounds ok to me. I added enough to make fluid and leach the rather thick mass of cyanide-impregnated charcoal fragments that were an inevitable part of my production process. I let the mixture stir for maybe 45 minutes before filtration in hopes of leaching most of the cyanide from the charcoal.

However, I'd say that I stirred my cyanide solution into something like 3 or 4 times its volume of 95% ethanol, which seems to be a considerably higher ratio than what you used. 95% ethanol is fairly expensive for me so I've also used the painter's "denatured alcohol" that contains methyl isobutyl ketone and (according to the MSDS) up to about 50% methanol. That seemed to work ok too. I had to wash the wet solid with a little 95% ethanol after precipitation to get rid of that MIBK odor.




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Taoiseach
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[*] posted on 18-5-2010 at 10:39


Well NaCN is slightly more soluble in water than KCN so maybe I should try the sodium salt next time. Could be its easier to crystallize also.

What yields did you achive? Did you analyze the product's purity or use it in any subsequent synthesis?

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[*] posted on 18-5-2010 at 11:39


My analytical methods were extremely crude. I did a qualitative cyanide test (not that I really needed it, given the smell) preparing prussian blue from mixed iron II/III salts. I also checked for carbonate contamination by adding a small quantity of the cyanide to ice cold dilute hydrochloric acid -- absence of bubbling indicated little or no carbonate. I searched for a simple method to analyze mixed cyanate/cyanide, as I suspected cyanate would be the greatest remaining impurity, but did not find anything at the time.

I subsequently used my cyanide with success to prepare a few different copper and nickel complexes, dissolve gold foil, plus (of course!) prepare a larger quantity of the lovely prussian blue.

I suspect production could be more elegant, and done on a larger scale, by using an electric furnace instead of combustion based heating. However I never needed it on a large scale and so had little incentive to scale up. Making 20 grams or less at a time was fine for me.

Thermal decomposition of ferricyanides or ferrocyanides is probably simpler. I do like the carbon reduction of cyanate because the raw materials are so very inexpensive and widely available.




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Formatik
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[*] posted on 18-5-2010 at 18:13


This reminds me of my first preparation of cyanide, which was incidental. I wasn't trying to make CN-. I melted alkali carbonate and urea in an open ceramic dish. Then applied stronger heat. I removed the heat after enough gas release, when cool, a strong bitter almond odor was emanating from the solids. Letting it stand longer in air caused a powerful bitter almond odor to form. Cyanide can be smelled before it kills you, and like Taoiseach says, it can be smelled once but then not continuously. Don't get too sniff happy. I was trying to form cyanate! I must have heated too strongly and despite being in open air, it still formed a significant amount of CN-. I found the maximal yield possible by thermal decomposition of potassium cyanate, and mentioned it here. I destroyed it with aq. permangante.
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[*] posted on 18-5-2010 at 19:01
Measuring Cyanide in any solution


Hi Poverone
You are a few years ahead of me. I am doing a lot of reading about Cyanide before making a bit to disolve gold from my many prospecting trips and mountain climbing. The best info besides your experiment has come from a website by Dr. A. K. Williams from San Pedro, Costa Rica. He has a huge website: http://www.prospectorsparadise.com where he gives excellent instructions in plain english on "Determination of Free Cyanide in Solution" using 13.07g of Silver Nitrate and a Titration setup. You have to get a 25 or 50cc burette in 0.1cc divisions and do the thing with the eye dropper, watching for the point where one drop forms a cloud which does not dissolve. He does all the math for you including Molar Mass and buffering which is way beyond my skills! Anyway, you can then know your exact Cyanide amount in percent and produce no extra toxic chemicals to worry about (5mg = Lethal Dose!).

Dr. Williams quit working in the USA and tries to educate the people who burn "Dore"-Mercury amalgum gold/silver globs in town resturants to show off the purity of their gold panning claims in South America, releasing all kinds of toxic Mercury fumes. Read through the entire website, its awsome!

Another website suggests a thiosulfate solution is best to destroy slight traces of Cyanide before throwing away those burnt soup tins etc.
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[*] posted on 1-12-2010 at 09:52


People always amaze me how can they make life so difficult, 16 pages and almost eveything is trash , melting something with something , cyanohydrin ?? when we want kcn who is need to synthesis cyanohydrin. WTF ? Buy ? so buy kcn. Ok there is no easiest way to obtain pure (99%) kcn then HCN introducing into alcoholic solution of koh , here you have:




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If someone want to say is dangerous so maybe quit chemistry at all
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entropy51
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[*] posted on 1-12-2010 at 14:46


Good Lord. Posting Jared Ledgard's crap on Science Madness. Have you no shame?
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[*] posted on 1-12-2010 at 15:34


mario840, it's really easy with the cyanate process Polverone discovered.

Simply melt urea with sodium hydroxide to yield cyanate, grind it finely with charcoal, load into a steel can, cover the top with loose aluminum foil, and blast it with a hot charcoal fire until flames (burning carbon monoxide produced by reduction of cyanate) cease to spew out from under the foil. I used a pair of hair dryers, bathing the can in sheets of brilliant white flame; probably overkill, but it did the job.

I believe I extracted the cyanide with cool water and then crashed it into a large volume of cold isopropanol to precipitate it.

An aqueous solution of said precipitate did not bubble on addition of citric acid at 10C. It did at something like 30C. Took that as evidence enough it was successful - I lacked the facilities for further analysis, and was not about to do a smell test!

As Polverone said, be careful about leaving it exposed to air, especially while still hot. Don't leave it in water for long periods of time either, particularly hot water - it will hydrolyze.

[Edited on 1-12-2010 by madscientist]




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[*] posted on 1-12-2010 at 19:49


i tried the method mario840 posted . i used distilled water and koh as recipient. it turned to ammonia after a day and precipited a salt. still at the bottom right now after 2 or 3 months. i then tried ethanol and koh. it did not turn to ammonia. i tried to dehydrate it slowly and it never dried after days of warming but turned to paste.both turn dark blue with iron sulfate. both make good plating solutions but niether will dissolve gold on their own. i tried the sodium carbonate and urea method but only got as far as making the cyanate and did not heat the precipitate with charcoal as mad scientist states. i missed this part in the 16 pages of literature . so i will try again. i also have gone through these posts for month and obviously im missing something. polverone states his salt dissolves gold leaf. that is my goal! i tried to contact my dear boy myfanwy and almost came to tears as i watched his channel.the boy actually succeeded and made a video. he was a MAD SCIENTIST.
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