Sciencemadness Discussion Board - Cyanate to cyanide - fresh thread

Cyanate to cyanide - fresh thread

Polverone - 27-6-2003 at 12:56

The other cyanide thread was getting long. Browsing through Ullmann, I see it says that potassium cyanate melts at 315 degrees celsius, and its low melting point (compared to the sodium compound) allows for a purer cyanate to be prepared since no solids remain intact during the synthesis. I find this interesting because both Lange's handbook of chemistry and the CRC handbook of chemistry and physics have "decomposes 700-900 C" for potassium cyanate's melting point. It seems they may both be deriving from the same incorrect source.

I don't really want to make potassium cyanide, because it is not as effective as sodium cyanide in some reactions. However, I do want to find more about something else:

"In the dry state, cyanate salts decompose above 450 °C to form cyanides. The decomposition is influenced by certain metals."

I would like to know what those metals are. Perhaps the print edition of Ullmann explicitly mentions them? It may be that I've been barking up the wrong tree with converting cyanate to cyanide. I know that my method works, but it might be easier/faster if I could learn what metals accelerate this transformation.

Organikum - 27-6-2003 at 15:12

Sorry this is slightly off but as I found it whilst after everything whats cyanXXXX for to satisfy Polverones never ending appetite on these compounds I dare to tell:

cyanogen iodide
use: generally for destroying all lower forms of life.

says the MERCK.
Wow! Take some cyanogen iodide and disperse it equally - what survives is a higher form of life! The age of the cockroaches is coming!

Iv4 - 29-6-2003 at 04:28

Interesting.Anything ele on this like how it's dispersed?

Organikum - 29-6-2003 at 04:57

very carefully, I guess?

Iv4 - 29-6-2003 at 17:53

LOL,I meant can it be put next to a charge or will it decompose?and stuff like that.

DDTea - 29-6-2003 at 19:42

Getting off topic a bit:

Cyanogen Halides were used as Chemical Weapons during WW1, but mainly Cyanogen Chloride and Cyanogen Bromide. I know CNI was suggested, but I'm not sure if it was ever used...

However, CNI can be used to attach the -CN group to Phosphate molecules in Nerve Agents

.

To answer your question though, I believe it would have been dispersed through pressurized tanks, like CNCl or CNBr.

...Now, to suggest a possible answer to the question of what metals to use...

What about Iron or Magnesium or Aluminum? Basically, try a reactive metal... My knowledge in this area is rather limited, but my guess would be that at higher temperatures, such metals would "steal" the Oxygen from the Cyanate group. I say this because I know that Iron, even at normal temperatures, can be pyrophoric.

Sound logical?

[Edited on 6-30-03 by Samosa]

Iv4 - 1-7-2003 at 01:41

My knowledge in chemistry is prety limited(big surprise)but I think calcium might be a good idea since calcium oxide is prety easy under an acetlyne flame.Thoguh iron goes tetraoxide much easier.Guess you'r right about the magnesium.

[Edited on 1-7-2003 by Iv4]

vulture - 1-7-2003 at 02:10

Calcium metal? Why would you use that? Very expensive and hard to prepare. Just use Al, Mg or maybe even Zn.

Iv4 - 1-7-2003 at 03:20

No I meant calcium carbonate.But after looking up the reaction I see it's not practical,having to be at 1200 and all( I though it was much lower than that).Correct me if I'm wrong but is'nt red hot iron in water turned to tetraoxidee.I know this is'nt exactly relevent but my school chemistry is prety damn old.

Theoretic - 31-7-2003 at 06:47

Somewhere in the deep core of the old cyanide thread there's a few posts about
cyanate, with urea mentioned too. Since I saw an interesting reaction on synthesis of cyanates, I suggest a two-stage process:
Na2CO3+2CO(NH2)2=>2NaCNO+2NH3+
+CO2+H2O
NaCNO+C=>NaCN+CO
Edit: Since there's an equilibrium between cyanide+CO2 and cyanate+CO, I think the reduction of cyanates with carbon is irreversible.

[Edited on 31-7-2003 by Theoretic]

blip - 31-7-2003 at 16:15

Quote:

Correct me if I'm wrong but is'nt red hot iron in water turned to tetraoxidee.I know this is'nt exactly relevent but my school chemistry is prety damn old.

Don't you mean something along the lines of:
3Fe + 4H2O  Some high temp. > Fe3O4 + 4H2

Friedrich Wöhler - 7-2-2004 at 02:20

Hallo,

Over 3 years ago I testet building of NaOCN and NaCN by Urea. (Since I have no more time for chemical experiments I must search again my protocols I have written down at the time.)

I remember the following equation
Na2CO3+2CO(NH2)2=>2NaCNO+2NH3+
+CO2+H2O
was physical wrong, it had very bad melting characteristics because of that high portion of Carbonate.
Now I used Hydroxides for Carbonates. With much better melting characteristics I got cyanates too. (Naturally with another equation.)

In addition I remember a very different melting and decomposition between using Na- and K- cyanat.

Coming time, I also will test to force decomposition of Cyanate by using pyrophoric iron. It also can be, metals ar usable, very easily building carbonyles (nickel powder e.g.).

Greetings from good old Germany!

chemoleo - 7-2-2004 at 08:26

And how are you going to make pyrophoric iron? Decomposition of iron oxalate? I tried that once, it works nicely

- Just heat it up in a testtube and allow the CO2 to escape, but no oxygen/air to enter. Cool it down, and shake it out of the tube, it self-ignites!
Anyway, is it necessary to use Fe? How about other metals, Mg, Zn, Al, etc?

Friedrich Wöhler - 7-2-2004 at 12:04

Hi chemolo,

I think, it could be favourably to support this reaction by (dry) hydrogen gas. You anyway need an inert gas to safe that reduced iron. So you can support reduction using H2 instead of N2, Ar or so...
Furthermore maybe you can force decomposition of *OCN by vacua. I also think, this is one of them cases, a decomposition can take several ways (several equations) under several conditions.
Pyrphoric iron must be a famous catalyst. Pd or Pt would surely be some better, but what want you to do with Mg or Al ???

Bist Du auch Deutscher? Es kommt doch auf die katalyt. Eignschaften genau dieses Stoffes in dieser feinen Struktur an. Also nochmal, ich würde die Reduktion gleich im H2-Strom machen (Al und Natronlauge) und überhaupt alles so optimieren, daß der Zerfall von *OCN bei möglichst niedriger Temperatur erfolgt, warscheinlich wird dann die Carbonatbildung geringer, die Ausbeute besser.

Polverone - 7-2-2004 at 13:27

Quote:

I remember the following equation
Na2CO3+2CO(NH2)2=>2NaCNO+2NH3+
+CO2+H2O
was physical wrong, it had very bad melting characteristics because of that high portion of Carbonate.
Now I used Hydroxides for Carbonates. With much better melting characteristics I got cyanates too. (Naturally with another equation.)

It is recommended for lab work to use potassium carbonate to prepare potassium cyanate, since KCNO has a lower melting point and the mixture can fuse completely without the KCNO decomposing to produce any KCN. However, since I have not yet been especially interested in preparing cyanates, just cyanides, I have obtained pretty good results just using finely powdered Na2CO3, excess urea, and charcoal in a steel vessel (perhaps the iron has some catalytic effect?)

One of the problems I've had is that the initial mixture of fine powders is very low-density, so I can't fit a lot of it in a single vessel, and it also is slow to melt since it is slow to conduct heat. The final melt is considerably lighter than the initial charge (because of the removal of some components of urea and charcoal) and occupies maybe 1/5 the volume that it did when I started. Part of this is no doubt due to my use of grapevine charcoal, which forms an extremely fluffy, light powder.

I think it might be advantageous for me to try using NaOH instead of Na2CO3, since the much lower melting point should lead to better/earlier molten homogenization.

According to this <A HREF="http://www.showa-pk.co.jp/information/cyanate.html">manufacturer's page</A>, the thermal decomposition of KCNO always causes some loss of nitrogen and leads to products that are somewhere from 1/4 to 1/3 K2CO3, the balance being KCN. I would presume that NaCNO decomposes in a similar fashion, if that page is correct. This is undesirable if one wishes to have pure cyanide on hand.

I have always used charcoal with my cyanates rather than heating them alone, hoping for a straightforward reduction of MCNO + C to MCN + CO. I don't know how successful I've been. When adding some of my product to cold aqueous acid, I see very little initial bubbling, whereas I would expect to see considerable bubbling if my material were 1/4 Na2CO3.

I know that my cyanides can always be purified, in theory, by adding cold acid to expel CO2, then distilling the HCN at a slightly raised temperature into an alcoholic solution of KOH, which will precipitate pure KCN. But that's a lot of extra work and hazard.

I suppose the reasonable thing to do is to analyze a sample from the next batch I make. Prussian blue can be precipitated nearly entirely (I believe), dried, and weighed, thereby enabling me to calculate how much of the original weighed sample of "cyanide" was actually a cyanide.

Edit: I just noticed another thing on that manufacturer's page:
"It reacts with urea with formation of biuret { NH2 ( CONH ) 2 } ." Another yield-harming reaction? Is the use of a large excess of urea not a good idea? So many questions that I must answer!

[Edited on 2-7-2004 by Polverone]

Friedrich Wöhler - 8-2-2004 at 05:11

Hi Polverone,

OK, you and I, we have different requirements about extra working and we have different private conditions. In my Country nevertheless NaOH is easy to get and not expensice. And... KOH you can buy here in a lab-shop in kilograms without getting arrestet into prison at the moment.

. Coming time I'll let follow my equations for reaktion MeOH + urea.
You correctly write, you anyway got a homogene melt only when used much more urea as the equation says. OK, your products where carbonate-free. My own ones too! But for it your product is contaminated with urea's decomposition products (biuret etc....) If it's to much work for you (as written) to clean your product, then its indifferently using hydroxide or carbonate. I remember reading about cyanide's cultural history, Justus von Liebig's product, he selled 200 years ago in his drug store in Germany ("Liebigs Cyankalium"

contained untill 40% of K-cyanate!! If Liebig (!) got never a clear product without extra cleaning -- how want YOU to get success easily?

My experiments using carbonates in theoretical proportions failed all in preparative problems! Homogene melt was impossible because of carbonate's big volume. Usably only with an excess urea. A general problem here is also that fucking foaming. You cannot take a bigger volume of mixture in your melting container. Forthermore foam is shit against homogene warming.
By the way...have you seen, if remaining coal with its different density is swimming on top of finished melt or sitting down on container's ground?

By the way - be sure avoiding exposition of reaktion gases (inhalating or contamaining your room) Ammonia's strong smell will cover all other ones. I am sure, that exposesd gas contains HCN (built by remaining moisture or CO2) or dust of alcali cyanide or ammonium cyanide!

As a general question - if administrator agrees, I see it as favourably adding text in user's own language to the English one. Makes it easier for many users in this multinational forum.

Hallo Polverone,
gut, wir haben warscheinlich verschiedene Ansprüche an den Arbeitsaufwand und verschiedene private Voraussetzungen. In meinem Land ist zumindest NaOH leicht zu bekommen und nicht teuer und KOH kann man auch leicht kilogramm-weise im Laborbedarf kaufen, ohne gleich verhaftet zu werden. Bei Gelegenheit schreibe ich auch noch die Gleichungen dazu, für die Umsetzung MeOH + Harnstoff.
Du schreibst richtig, daß Dir eine homogene Schmelze sowieso nur mit einem erheblichen Überschuß an Harnstoff gelungen ist. OK, Deine Produkt war Carbonat-frei, schreibst Du. Das war meines auch! Dafür hast Du aber erhebliche Verunreinigungen aus Zersetzungsprodukten des Harnstoffs drin! (Biuret ect...). Wenn es Dir zu viel ist - wie Du schreibst - das Produkt zu reinigen, also ein verunreinigtes Produkt akzeptierst, ist es sowieso egal, ob Du nun von Hydroxid oder Carbonat ausgegangen bist.
Ich erinnere mich, in der Geschichte der Cyanide gelesen zu haben, daß Justus von Liebigs Produkt ("Liebigs Cyankalium"

vor 200 Jahren bis zu einem Drittel Kaliumcyanat enthielt. Wenn Liebig (!) es nicht ohne Extra-Reinigung gelang, 100% KCN zu erhalten, wie willst DU es dann bekommen?

Meine Versuche mit Carbonaten im stöchiometrischen Verhältnis zu Harnstoff jedenfalls scheiterten alle! Das Gemisch war nie homogen zu schmelzen, wegen des großen Volumens des Carbonats. Ein generelles Problem hier ist auch das scheiß Schäumen, Du kannst kein großes Volumen in einem kleinen Behälter auf einmal schmelzen, es schäumt über. Außerdem ist das Schäumen ja auch Gift für die Wärmeleitung. Übrigens, hast Du Beobachtungen gemacht, wie die Cyanid-Schmelze erstarrt, wenn Du einen Überschuß an Aktivkohle verwendet hast? Wie ist die Dichte der beiden Stoffe? Schwimmt die Kohle auf dem geschmolzenen Cyanid oder setzt sie sich ab?

Übrigens, denke daran, daß Du von den Abgasen dieser Prozesse nichts inhalierst, ich bin sicher, das abgehende Ammoniak (das alle anderen Gerüche übderdeckt) wird auch HCN enthalten (aus Restfeuchte und CO2), bzw. mitgerissenen Staub aus Kaliumcyanid oder Ammoniumcyanid!

chemoleo - 8-2-2004 at 10:26

Hi Friedrich Woehler

The problem is if everyone started posting in their own language to make it easier for potential countrymen to understand, you'd have many posts half in chinese, portugese, spanish, french, russian, german and so on.
This would make this forum very cluttered. I think (despite me speaking German too) we have to accept that English is the language of the forum, and the main language in the Internet. By the way, it is a lot of work, too, to first write the post in your own language, and then to translate it after. It may be a lot less time-consuming to write it in English right away, and then read through it to remove any mistakes you notice.

Anyway... could you elaborate why you need pyrophoric iron to produce cyanide from cyanate? You make it sound like it is a catalyst. I understood it to be an oxygen acceptor, whereby the iron gets oxidised and the cyanate reduced to cyanide. But I guess I was wrong...

Polverone - 8-2-2004 at 11:33

I have no problem getting KOH or NaOH. I have just never tried using them for this prepartion before because the carbonates seemed to work fine and were less expensive. I am sure that no biuret or any other organic compound survives in my final product. I heat the reaction vessel until it glows orange, and hold it at that temperature for several minutes.

I have never experienced any problems with foaming, either. Here is how I have worked in the past:

Heat sodium hydrogen carbonate NaHCO3 (baking soda) strongly in a glass dish until it expels carbon dioxide and water and it is transformed into anhydrous Na2CO3 (this leads to a fine, dry powder).

Mix the Na2CO3 with the weighed amount of urea pellets. In portions, pour the mixture into a coffee grinder and grind it into a fine mixed powder. (Cyanuric acid may also be used in place of urea.)

Grind the charcoal in the coffee grinder.

Stir the charcoal powder into the mixture.

Pour the powder into a steel soup can.

Place the soup can in a charcoal or wood fire, and protect its contents from the air (by setting a flat, heavy piece of steel over the top of the can, for example). The can's contents will slowly melt down as the portion at the bottom becomes liquid and more compact. Ammoniacal fumes will escape the can during this process. You can lift the steel lid briefly, once in a while, to check on its progress. When the contents are all melted down and glowing red-orange, you will see bubbles rising to the sufface and burning with a small "pop" and a yellow-orange flame. I presume that this is carbon monoxide, burning yellow because of sodium compounds. The charcoal remains homogenous with the melt, being "wetted" by it. After some time at high heat (30 minutes, maybe) the bubbling has virtually ceased and I consider the reaction complete. The reaction can be made to go faster by feeding extra air to the fire with an air compressor or fan to raise the temperature.

I remove the can from the fire and let it cool, still protected as well as possible from the air with its steel lid. When it has cooled, I break the solid mass out of the can with a hammer, and pound the lumps into smaller pieces. These pieces are placed in warm water and left for several hours, with occasional stirring or shaking. The lumps eventually dissolve and break up.

The cyanide solution is then filtered to remove the remaining charcoal. If you want to eliminate all charcoal, even the finest particles, using a layer of celite in the filter helps.

The cyanide-bearing charcoal waste is added to an excess of household chlorine bleach and left for a day to oxidize the cyanide. It can then be flushed down the toilet or disposed of in ordinary garbage.

The cyanide solution is poured into an excess of denatured alcohol and stirred until the cyanide appears as solid particles. Then the mixture is filtered to recover the solid sodium cyanide. This wet cyanide is pressed between layers of paper towels to remove most moisture. It can be finally dried over NaOH, or just used as it is.

The cyanide-bearing paper towels and alcoholic liquid can be combined and burned, remaining residue again being treated with chlorine bleach before its final disposal.

Friedrich Wöhler - 8-2-2004 at 12:07

Quote:

Originally posted by chemoleo
...chinese...

*loool* Ok, I am just installing the chinese language file. Ahhhm...if you a German too, you will sure know the name of the chinese transport minister: Um Lei Tung.

OK, I admit, I'm a little confused at the moment. We speak about two different shoes: catalizing self-decomposition or reduction. There are several decomposition-equations for *OCN: to lost *O or disproportion under building of CO and N2 or both shoes together. I also understand, why we speak about coal (activatet coal) at first. Its cheaply and easy to get. But required a higher temperature and I think, in lower temp is the *O-splitting-off prefered and in higher temp the disproportion. I think, pyrophoric iron can work here in its both characteristics: as catalyst and as *O-acceptor. I believe, that activ iron could (mixed with *OCN and heated under O-free atmosphere) take the oxygen over at LOWEST temperatures already! Again: I know why we speak about coal at first: oxalic acid is heavy to get, expensiv and bulding that iron a complexed extra work.
I believe its time for me to test act iron made by FeCO3 reduced by H2. (A lot of Fe(II)* you can easily buy (in EU) as Fe-fertilizer (Deutsch: Eisen-Dünger), its FeSO4.

Deng Xiao Ping, Hua Quo Feng!

Polverone - 8-2-2004 at 12:59

I used charcoal to attempt the reduction of *CNO to *CN because when I first thought of the idea, I was unable to find any information about the reduction or thermal decomposition (catalyzed or otherwise) of *CNO. I have continued to use it because it seems to give acceptable results for the things I have tried to do with it so far.

Oxalic acid is inexpensive and easy to get in the US, so that is not a problem for me. However, heating cyanate with pyrophoric iron under an inert atmosphere does not seem so simple or easy. I would sooner try to purify my crude cyanide by acidifying and precipitating KCN from an alcoholic solution of KOH with HCN, as mentioned earlier.

Friedrich Wöhler - 8-2-2004 at 15:27

Hi Polverone,
your complete life must turn arround problem of building cyanides...

Maybe I can do a good work for you: In a moment as I searched for solutions to build gold- or platin-anodes per galvanic way, I collectet many informations about getting cyanides. For example I searched also in a library of a university. There are really many ways. As one example I read: Ammonium formiate decompose by heating to HCN and water. NH4COOH ---> HCN + 2 H2O
Please keep some patience, I will post my collected informations in next days I have written down in last 3 years.
Unfortunately I still couldn't find a way to easy get oxalic acid in Germany. Maybe one of other German users can give me an info. Possibly, its an agricultur produkt? I found it under chemicals for paint artists:
http://www.kremer-pigmente.de/bindem03.htm (in German "Oxalsäure", Prize in Euro included tax) 56,50 € for 10kg is not expensiv, but what artist buys 10kg ???

Friedrich Wöhler - 8-2-2004 at 19:23

Quote:

...decomposition of *OCN by vacua ...

I remember...for several experiments I used a 2-kW-compressor of an air conditioner, isolated its electric connectors (220 Volts) with silicon and let that machine run completely under circulating cold water. (That's the onliest way to cool that machine enough while such abusing.)
Forthermore, I would give 1000 Dollars, could I know, where is the borderline between decomposition to cyanid and decomposition to the free alcali metals...

notagod - 9-2-2004 at 05:12

Hi Friedrich Wöhler!

In Sweden you can get it easily in paintstores, but also in supermarkets that sell dyes for home coloring. In this case only 100 gram bags thou.

Friedrich Wöhler - 10-2-2004 at 03:28

Hi Swedish friend,

are you in Sweden posting to here with your computer under 3 meters of snow?

After tragical attac on Anna Lindt one could see that Sweden must be not such kind of a "police state" like Germany or UK e.g., because of Swedish police needed forensic help from criminal police of other states. Also maybe there is a not so cramed climate to buy or order chemicals as a private man.
In the example I posted
http://www.kremer-pigmente.de/bindem03.htm
you can see, also such as nitric acid (in German "Salpetersäure"

and so on are available. Maybe ordering 1 kg of oxalic acid you will no cause heavy distrust there. But to order nitric acid e.g. I'd have a not good enaugh feeling. On the other side...every small boy can easily buy a quicksilver containing electric niveau-switch. But I feel not good buying pigment "zinnober" (HgS) beeing not a painting-artist, everyone knows, its easy to convert to Hg or soluble Hg-chemicals.

I love Astrid Lindgren !!!

notagod - 10-2-2004 at 12:41

Hi again!
No, there isn't much snow here now (only in the northern parts of country) and I like it like that (hate snow).
In the Anna Lindh case I believe they said in the news that there was a new method to extract or sample DNA, that only the English forensic labs had the knowledge or equipment to use. English police labs are the best in Europe regarding DNA work and Swedish police didn't want the same thing that happend in the Olof Palme case happen again.

The problem with obtaining chemicals in Sweden and other countries is that stories use common market logic to run their business, i.e if the customers don't buy a product, they will not sell it. Sweden has only approx. 9 millon people, so there is not many hobby chemists, the demand isn't high enough

. Otherwise you could buy a lot of stuff. Usually the paintstores (färgaffärer) has it, but the one I looked in sold things by 25, 50 Kg or so, perhaps more and that was too expensive and they had to order it. Private persons usually need a permission to only some chemicals, for instance conc. sulfuric and nitric acid and toxic chemicals. (side note: doorsales person and stupid housewife :mad:

). There are some exceptions, to buy 100% metanol for example, you don't need permission. Another problem is that companys like merck doesn't want to sell to private persons, to much of a hassle for them, low quantity orders and the ever present "terrorist threat".
Mercury containing compounds is forbidden since some years ago, no new switches or thermometers with mercury today, (which is good I think). Exception: pharmaceuticals?.
You don't have to order oxalic acid, it is in supermarkets in the dye section, for coloring clothes and stuff, at least in some stores.
Mineral shows are fun

(do you get it?)

Besides, registering a company in Sweden is easy, at least last time I checked.

Astrid Lindgren maybe wrote nice children books, but messed up Sweden with her thoughts on "animal rights". Well perhaps not totally, but some.

Friedrich Wöhler - 13-2-2004 at 06:41

Hallo Swedish friend,

Its nice to know, you must not search on your keybord for the "ö" in my nick...

Hi Polverone,

I don't know, if bulding ammonium cyanide from coal and ammonia is discussed already anywhere in forum.
Want we to think about together? I have a detailed picture in my head, how to do this practically. But: I still found no information about the needed temperature running this reaction.

I just opened a new thread (my first own opening) about reactions from dry ammonia. It where a good place, if that is still undiscussed.

By the way...what are the English trivial names of solutions of ammonia and of alcali hydroxides and CaOH-suspension?

Polverone - 13-2-2004 at 17:06

No, the production of ammonium cyanide has not been discussed here. I recall from <A HREF="http://bcis.pacificu.edu/~polverone/muspratt.html">Muspratt </A> (or perhaps the <A HREF="http://www.1911encyclopedia.org">1911 Encyclopedia</A>

that a mixture of natural gas and ammonia yields some ammonium cyanide when burned.

Trivial names:

An aqueous solution of ammonia is often called ammonia water, ammonium hydroxide (somewhat of a misnomer), or simply ammonia. NaOH is called lye or caustic soda (this second name is antiquated). KOH may be called caustic potash (this is also an antiquated name). Ca(OH)2 is called slaked lime.

S.C. Wack - 9-3-2005 at 23:21

I recall reading somewhere that ammonium cyanide sublimes by heating a mixture of ferrocyanide and ammonium chloride. No details on yield though. Anyways, I ran into this cyanate to cyanide experiment on Gallica so I thought I'd throw it up FWIW. It is, of course, in French.

I think that the yield is good considering the reaction is more like: 5 KOCN -> 3 KCN + K2CO3 + CO2 + N2. Thus the use of waste CO over the hot cyanate in patents.

[Edited on 10-3-2005 by S.C. Wack]

Attachment: compt_rend_161_308_1915.pdf (75kB)
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shelf life of potassium cyanide and CO2

prole - 10-2-2006 at 11:48

According to the Merck Index, KCN decomposes gradually by contact with CO2 and moisture. Is there a substance that one could wrap in a tea bag and insert into the KCN-containing bottle that will absorb CO2 and not react with the KCN?

Does anyone know the shelf-life of KCN in a sealed amber jar?

I may soon prepare a small quantity from HCN and KOH, and I don't want to lose any to CO2 or moisture after the gas-generating ordeal, unless the losses are negligible, because I don't ever plan to prepare more. I've seen a lot of commercial CO2 absorbents on google, but I'm wondering if there's something more OTC that could be used. Thanks for any responses.

-prole

hinz - 10-2-2006 at 12:49

Prole I think that the KCN will not decompose if it comes in contact with water and CO2.
The CO2 and the water react with each other forming carbonic acid.

CO2 + H2O <==> H2CO3

Since HCN is a very weak acid, carbonic acid, which isn't also a strong acid, will liberate the HCN from KCN or oher cyanide salts. But if your storage container is closed the HCN can't get out of it and the whole reaction stays in its equilibrium.

H2CO3 + KCN <==> HCN + KHCO3

So, there is no need of a CO2 absorbent in a storage container, if there is no excange with the air. I think the shelf-life of KCN in a sealed jar is nearly unlimited. (if it's really well sealed)

[Edited on 10-2-2006 by hinz]

6dthjd1 - 22-2-2019 at 13:22

Has anyone tried the method of combining Cyanuric acid, potassium carbonate , and charcoal in an effort to make potassium cyanate which is then reduced to cyanide?

Essentially this is analogous to Polverone's method involving the sodium salts.

I have done this process and upon testing a chunk of my suspected potassium cyanide with a cyanide test kit strip no detectable cyanide was found.

This is interesting as I found limited evidence that the substance seemed to be deliquescent. Potassium cyanate is not deliquescent.

walruslover69 - 23-2-2019 at 10:26

Quote: Originally posted by 6dthjd1

Has anyone tried the method of combining Cyanuric acid, potassium carbonate , and charcoal in an effort to make potassium cyanate which is then reduced to cyanide?

Essentially this is analogous to Polverone's method involving the sodium salts.

I have done this process and upon testing a chunk of my suspected potassium cyanide with a cyanide test kit strip no detectable cyanide was found.

This is interesting as I found limited evidence that the substance seemed to be deliquescent. Potassium cyanate is not deliquescent.

I have tried this with sodium carbonate and it did produce some cyanide. The separation was a pain and i have no idea about the purity, but when i dissolved some of the solid in water, and added it to a solution of HCl and dissolved iron, prussian blue precipitated indicating some amount of cyanide.

6dthjd1 - 23-2-2019 at 15:40

How did you separate? Did you use methanol with vacuum removal of methanol or slow evaporation on cold, dry winter days or a more inert atmosphere?