Sciencemadness Discussion Board - Preparation of cyanides

He had better not let Scotland Yard or MI5 know about his intentions!

I assume they know everything posted here, don't you?

Wow

Sakamura - 22-9-2009 at 17:49

I did not think I would get this type of response! Yes I assure you I am a Dr trained in the UK. We never make solutions everything is pre packed and pre measured. It's not like Victorian times. You do not make up a solution of normal saline by adding NaCl to water - you pick up a bag of it. Same with drugs, if it's a solution you pick up a vial with it all pre made. On extremely rare occasions (I have never had to do it) when a solution needs to be made up the pharmacist does it for you. You seem to have a distorted Idea of what a modern Dr's job entails. Even the Formaldehyde solutions used in specimen fixation in histopathology were pre made.

No my questions have not been answered already as it is mainly about Ferro not ferri.

A molecular and cellar biology or pathology lab is completely different to a physical chemistry lab. I am comfortable in the former but not in the later (sorry for that misunderstanding), so as far as physical chemistry goes I am a beginner.

My Bio is not mixed up - actually it's pretty standard. Med school ->intercalated BSc ->Finish med School and do the jobs best suited to your ultimate speciality.

I realised a first post about making something so toxic would raise eye brows and get replies about doing something very safe and very boring first, like growing crystals but not to this extent. To me boring = lack of interest learning nothing and giving it up. The converse applies.

I really thought this board was going to be helpful - obviously I was mistaken and apparently I am not welcome. Oh well Chemistry is not the only thing I am interested in so I will probably abandon the whole thing and move on to another field - which is a pity. At least the government will be pleased there will be one less amateur chemist.

All the best and no hard feelings.

[Edited on 23-9-2009 by Sakamura]

Magpie - 22-9-2009 at 19:10

Please understand our natural reticence to provide a recipe for KCN via HCN to someone so rusty or inexperienced in the art of chemistry. Making cyanides is a preparation we recommend that only highly experienced and knowledgeable chemists try. There are a lot of kewls out there that don't know shit and will try anything. We don't want your premature demise on our consciences. Besides that, it would be extremely bad publicity for this forum - might even get it shut down.

Your approach to using full safety gear and conducting the preparation outside, hopefully with a little breeze, or perhaps a fan, is a good approach. The procedure should be fairly straightforward and I believe is adequately described in this thread.

So, if I understand you right, you are looking for a recipe? You are probably not going to get it in public from this site. Perhaps someone will U2U a recipe.

Can't you just buy it? As a medical doctor I would assume you can buy most any chemical. Is this not true? If you are just shy about having a record of you buying a cyanide...well I certainly understand that.

entropy51 - 23-9-2009 at 05:43

Quote: Originally posted by Sakamura

I did not think I would get this type of response! Yes I assure you I am a Dr trained in the UK. We never make solutions everything is pre packed and pre measured. ..... You seem to have a distorted Idea of what a modern Dr's job entails. Even the Formaldehyde solutions used in specimen fixation in histopathology were pre made.

No my questions have not been answered already as it is mainly about Ferro not ferri.

A molecular and cellar biology or pathology lab is completely different to a physical chemistry lab. I am comfortable in the former but not in the later (sorry for that misunderstanding), so as far as physical chemistry goes I am a beginner.

My Bio is not mixed up - actually it's pretty standard. Med school ->intercalated BSc ->Finish med School and do the jobs best suited to your ultimate speciality.....

I really thought this board was going to be helpful - obviously I was mistaken and apparently I am not welcome. Oh well Chemistry is not the only thing I am interested in so I will probably abandon the whole thing and move on to another field - which is a pity. At least the government will be pleased there will be one less amateur chemist.

All the best and no hard feelings.

[Edited on 23-9-2009 by Sakamura]

Sakamura, I am an M.D. trained in the U.S. and I agree that we don't normally have to make dilutions.

However, part of that training was in general, organic and biochemistry. We spent much time in the labs and we had to learn how to calculate stoichiometry and perform dilutions.

I have also worked in, and supervised, cellular biology labs. Calculating and performing dilutions was something we did for every experiment because solutions had to be accurately made up. Except for very basic reagents and culture media nothing that we used was available pre-packaged.

I'm sorry that you feel put off because your request was met with skepticism, but had you made yourself known to us before asking about KCN the response would have been different.

Ferricyanide is mentioned in this thread.

Books in the forum library and elsewhere on the web would answer most or all of your questions. The fact that you would give up your newfound hobby because of a single encounter with this forum makes me doubt your seriousness.

If you are really interested in chemistry then stick around and participate in our discussions. Much is to be learned here, and even more so in our library.

If your chemical skills are rusty you absolutely should not practice them by preparing HCN.

chloric1 - 23-9-2009 at 08:14

Agreed. Even in the "good 'ol" days of the 1920's and 30's, most introductory labratory manuals would start you off slow and work up your skills to handle the specially deadly proceedures like cyanide, bromine, HF, and others. We at sciencemadness follow loosely this same approach. Learn manipulations while working with the more benign substances first. Heck you can fill an afternoon playing around with sodium silicate and/or borate

Personally, I have chosen not to mess with cyanides because I don't feel I have enough safety gear. I feel confident in handling the glassware and equipment but I need to implement a series of safety measured before I can even consider HCN preparation.

entropy51 - 23-9-2009 at 10:18

Hydrocyanic Acid Reference

I have posted a reference on production of HCN from ferrocyanides and ferricyanides in the currently active References Wanted thread in the References section of the forum.

Sakamura - 23-9-2009 at 18:56

Thank you entropy51. Training for a MBBS in the UK or an MD in the USA is obviously very different. I asked a few colleagues if they can do the stoichiometry calculations required accurately and the answer was universally well theoretically yes but I have never done it, why don't you ask a chemist to do it? They do it all the time. I.e. they to would want a check as well, have never done it and are non too confident of their ability to get it right first time. But it does not matter - you are the experts not me, so I will take your advise and put this project on indefinite hold and do much more reading before I attempt anything and it won't be anything as hazardous as KCN .

densest - 23-9-2009 at 20:59

@sakamura - wise to keep cyanides on hold. The great hazard of -CN as with H2S is that it paralyzes respiration very very quickly. H2S is actually more toxic (?10X?) and more common but the smell keeps people from getting killed. Still, some large alga blooms on French beaches this year have killed at least one person and a horse due to H2S emitted during decomposition. Either one can be detoxified if in small enough quantities - emphasis small.

I've worked with cyanides and many other highly toxic materials and am still around to write. Some of it was dumb luck. Most of it was reading what the conditions necessary for toxicity (amounts, pH, compounds, etc.) and a very clear idea of how many little droplets and particles drift from the equipment despite my most careful efforts. You can get away working with almost anything inorganic chemical at 1 - 10mg quantities (with some glaring exceptions) - it's an interesting art getting useful data at that level. A draft away from you into an activated charcoal filter (replaced frequently) can be a lifesaver, along with a big dishpan full of water into which to drop any test-tube which might have a reaction getting out of control. Small test tubes! Disposing of the water later might be a problem. It's a much better problem than going to hospital or the morgue.

Good luck and enjoy your experiments!

Well you have me convinced

Sakamura - 24-9-2009 at 21:38

densest I hate to criticize fellow Dr's but the recent change in training has made things worse not better. I doubt an FP1 or 2 who will try to treat you first at secondary care level even knows about the electron transport chain. If I did it (and now I am not about to) I think if anything went wrong it would be an autopsy job - I have done enough of those and it actually horrifies me.

I had a chat with my old chemistry Master a PHD Chemistry (organic I think) and he agrees with you guy's. This stuff is way too toxic but he was very enthusiastic about teaching and I never had a boring lesson from him. He offered to get me to a safe level using his own lab on weekends but quite justifiably still does not recommend making KCN (although he admits he has done it multiple times himself). All I need to do is pay for the reagents and disposables (gloves etc and glassware that's not to hand) so I still have a chance to drink deep of the Pierian spring without killing myself. This is perfect for me i.e learning under the supervision of an expert instead of 'having a go' and praying.

Thanks for all your advice.

chloric1 - 25-9-2009 at 05:23

That is GREAT news. A REAL lab for you to practice in. I am really happy for you. I have a burning urge to ask what you want cyanide for? Making complexes, electroplating silver? As far as the complexes or organic synthesis you would have to wait. But for silver plating there are thiosulfate and iodide baths. I hear these are more expensive and more difficult to operate.

entropy51 - 25-9-2009 at 05:42

Quote: Originally posted by Sakamura

This is perfect for me i.e learning under the supervision of an expert instead of 'having a go' and praying.

Thanks for all your advice.

And you thought we weren't being helpful.

I told you should stick around. Mostly we are not a bad lot.

Sakamura - 26-9-2009 at 00:33

Again thanks for all your advice. I am pretty chuffed now having access to a Physical chemistry lab with some one that knows what they are doing as well as an organic lab. The only downer is that I know he will give me massive amounts of homework to do (or he did when I was at School) which is what is required but I doubt I will feel that way after a long day at work! So I may well be back for help on answering his questions which are never simple.

You all want to know what I want(ed) it for. Well I will give a very short over simplified explanation as it's a cyanide thread and my ultimate aim does not have much to do with cyanides. After I had got comfortable with working with them electroplating etc anything to get me back working comfortably in a Physical Chemistry environment - which is usually fascinating and I am sure I would have lots of fun on the way, all the more so if the thing was not so toxic. I probably overemphasized this in my previous posts. Ultimately (and this would take years including ethics comity approval and probably a grant) I intended to make a tissue stain that differentiates two cell types that wrap up neurons (nerve fibres) Schwann cells for the peripheral nervous system (PNS) and Glial cells for the central nervous system (CNS) without Immunofluorescence which is not cheap, doesn't last and is generally hard to work with, especially if you are double or triple staining. No stain is currently available 'off the self' that will differentiate between them but it can be made and it's main ingredient is KCN - buying it is an option if the lab has a licence, I don't know if it has, but I would be dubious of the purity and learn virtually nothing about chemistry. I did my BSc thesis in nerve regeneration (for the non medics the CNS does not regenerate - think superman dying paralysed, where as the PNS 'has a go' then gives up). I do not have the reference to hand but an Athens search of 'Schwann cell depots in frozen skeletal muscle grafts' will find it. I got PNS nerves with some encouragement to fully regenerate over a 4 cm gap in 3 weeks (although it isn't perfect for esoteric reasons it has been adopted in clinical practice). There are glaring holes in our understanding of nerve regeneration e.g 'why does nerve 1 the olfactory nerve (the one you smell with) regenerate fully with no help when no other nerve does?' I think I know why but I have to prove it. Hence my interest in pure KCN. I just wanted to make a stain, further my understanding of Physical Chemistry, have some fun along the way and hopefully do some good in the process - I realise now I should have explained this from the beginning but I got carried away with the idea. Again thanks for all your advice.

watson.fawkes - 26-9-2009 at 04:37

Quote: Originally posted by Sakamura

I intended to make a tissue stain that differentiates two cell types that wrap up neurons (nerve fibres) Schwann cells for the peripheral nervous system (PNS) and Glial cells for the central nervous system (CNS) without Immunofluorescence which is not cheap, doesn't last and is generally hard to work with, especially if you are double or triple staining. No stain is currently available 'off the self' that will differentiate between them but it can be made and it's main ingredient is KCN

Not to pry too much, but is the cyanide differentiation between these two cell types related to some function over and above myelination that one cell type has and the other does not?

Taoiseach - 27-9-2009 at 00:41

This is from "the industry of cyan compounds":

Ammonium cyanide, NH4CN, is a highly volatile flammable crystalline solid that smells like both NH3 and HCN at the same time. Boiling point is 36°C. It is highly soluble in water and ethanol and extremely toxic. Decomposes slowly at RT. It had some applications in industry because it is easily formed by leading dry NH3 over glowing charcoal. The NH4CN was then used to prepare KCN.

Synthesis of NH4CN: Mix 3 parts of potassium ferrocyanide and 2 parts NH4Cl and destill @100°C.
The vapours can be condensed to solid NH4CN.

Also, destillation of 3 parts potassium ferrocyanide, 2 parts NH4Cl and 10 parts water yields a dilute solution of NH4CN.

JohnWW - 27-9-2009 at 02:14

This is from "the industry of cyan compounds":
Ammonium cyanide, NH4CN, is a highly volatile flammable crystalline solid that smells like both NH3 and HCN at the same time. Boiling point is 36°C. It is highly soluble in water and ethanol and extremely toxic. Decomposes slowly at RT. It had some applications in industry because it is easily formed by leading dry NH3 over glowing charcoal. The NH4CN was then used to prepare KCN.(cut)

That method of synthesis, involving partial decomposition of NH3 under high heat over charcoal (presumably in the absence of air), is most unlikely to produce anything like pure NH4CN, and there would have to be some sort of purification. I am fairly sure that other volatile cyano-compounds like cyanamide, NH2CN (especially), HCN, (CN)2, HN=C(NH2)2, HN=C=NH, and possibly H2C=NH and HN=CH(NH2), would also be produced in significant to substantial quantities.

watson.fawkes - 27-9-2009 at 07:02

This is from "the industry of cyan compounds"

Would you provide a complete reference for this? I can't even find the title or any reasonable variants. Is it a chapter title in some other work?

Taoiseach - 27-9-2009 at 07:09

Yes don't even think about it, all sorts of crap would be in the destillate. This method is completely useless. There's more convenient routes to impure cyanide, most of which have been discussed in this thread.

The interesting part is that ferrocyanide+NH4Cl yields vapours of PURE AMMONIUM CYANIDE at a temperature as ridiculously low as 100°C. Besides, 100°C is a temperature most easily maintained by use of a simple water bath

Ammonium chloride sublimes at about 300°C so it should not contaminate the end product. What we have here is a method that rips off CN- from ferrocyanide and delivers it in a PURE form. The vapours can be condensed in a flask cooled in an ice bath and then reacted with KOH.

I hope the book doesnt bullshit us and this really works, because it sounds almost too good to be true!

entropy51 - 27-9-2009 at 07:12

The reference may be "The cyanide industry: theoretically and practically considered "
which is available as pdf on books.google.com

Taoiseach - 27-9-2009 at 07:14

Its a German book and available online:

http://www.archive.org/details/dieindustrieder00khgoog

Dunno if theres an english translation tough.

Taoiseach - 27-9-2009 at 08:10

The preparation from ferrocyanide+salmiac is also mentioned on wikipedia:

http://en.wikipedia.org/wiki/Ammonium_cyanide

S.C. Wack - 27-9-2009 at 08:52

It's a big jump from

"Le cyanhydrate d'ammoniaque se prépare très facilement par double décomposition. Un mélange de 1 équivalent de sel ammoniac et de 1 équivalent de cyanure de mercure desséché, entrent facilement en fusion à la flamme de la lampe à esprit-de-vin, et dégagent en abondance du cyanhydrate d ammoniaque, tandis qu il reste dans la cornue du bichlorure de mercure. On réussit pareillement, et d une manière plus économique, en substituant au cyanure de mercure le cyanure jaune de potassium et de fer effleuri."
http://books.google.com/books?id=c5s5AAAAcAAJ&pg=PA231

to

ferrocyanide+NH4Cl yields vapours of PURE AMMONIUM CYANIDE at a temperature as ridiculously low as 100°C

The research of Langlois, Kuhlmann, Bueb, Bergmann, Lance, Voerkelius, et al. with ammonia and carbon are known and available if you just search for them. Had the board not deleted the Beilstein file that I uploaded to this thread earlier in this post [why bother uploading anything when my files keep getting deleted, even small ones disappear], you'd be able to see the citations. Google to the rescue.
http://books.google.com/books?id=cR8SAAAAIAAJ&pg=PA40 (NH4CN)
http://books.google.com/books?id=cR8SAAAAIAAJ&pg=PA30 (NH3 + C)

The book mentioned by entropy51 is one of many books available on cyanides and their manufacture, it is a good one http://books.google.com/books?id=qE4wAAAAMAAJ

[Edited on 27-9-2009 by S.C. Wack]

JohnWW - 28-9-2009 at 04:02

Its a German book and available online:
http://www.archive.org/details/dieindustrieder00khgoog

The URLs for direct downloads of it, and full title, are:
http://ia310837.us.archive.org/2/items/dieindustrieder00khgo... 5.30 Mb or
http://ia310837.us.archive.org/2/items/dieindustrieder00khgo... 8.95 Mb
- Die Industrie Der Cyanverbindungen, Ihre Entwickelung Und Ihr Gegenwärtiger Stand - H Köhler (1914)

Taoiseach - 28-9-2009 at 07:42

Reduction of cyanate with C yields cyanide contaminated with carbonate. The books says that pure KCN can be obtained by leaching the fused mass with hot anhydrous ethanol.

Right now this looks like the most promising route to me.

Also cyanate can be reduced quantitatively to cyanide with CO gas at red heat. This seems to work with sodium cyanate only:

1. Sodium cyanate from sodium carbonate and urea: Na2CO3 + 2CO(NH2)2 -----> 2NaOCN + 2NH3 + CO2 + H2O

2. Sodium cyanide from sodium cyanate and carbon monoxide:
2NaOCN + 2CO -----> 2NaCN + 2CO2

About 8grams of 100% formic acid would yield the stochiometric amount of CO to reduce 10,7g NaOCN to 8g NaCN, no losses considered.

Taoiseach - 29-9-2009 at 08:29

Anyone has reliable figures on KCN's solubility in hot ethanol?

All I could find is a vague remark in Vanino's handbook of preparative chemistry, saying its solubility in boiling alcohol is "65%".

garage chemist - 29-9-2009 at 10:27

Ullmanns Encyclopedia says 0,57g/100g in 100% Ethanol at 19,5°C, and 4,91g/100g in Methanol at the same temperature. No other temperatures are given.

I've used Methanol with a Soxhlet extractor to extract KCN from the powdered residue of K4Fe(CN)6 fusion, and the residue from evaporating the MeOH on a boiling water bath in vacuum came out as 85% KCN upon titration with 0,1M AgNO3.

Jor - 29-9-2009 at 11:14

Interesting. You just heated ferrocyanide in a crucible? Is porcelain suitable? Ofcourse the product must be protected from moisture and oxygen, but that is not a problem, I will just cover the porcelain crucible with a porcelain plate. What temperature is required? Is a propane torch suitable?

I don't have a Soxlet, but I guess boiling in methanol with vigorous stirring is sufficient.

Is evaporating without vaccuum also suitable? I don't see why not.
Now the only problem is, how to purify the 85% KCN...
What were your yields?

[Edited on 29-9-2009 by Jor]

entropy51 - 29-9-2009 at 13:51

Quote: Originally posted by Jor

Interesting. You just heated ferrocyanide in a crucible?

Yep. See this book for this and other ancient but low tech methods: http://books.google.com/books?id=qE4wAAAAMAAJ

JohnWW - 29-9-2009 at 14:38

Quote: Originally posted by Jor

Interesting. You just heated ferrocyanide in a crucible?

Yep. See this book for this and other ancient but low tech methods: http://books.google.com/books?id=qE4wAAAAMAAJ

Its title is: The Cyanide Industry: Theoretically and Practically Considered (1906)
Author: R. Robine, M . Lenglen, J. Arthur Le Clerc, Charles Edward Munroe
Publisher: J. Wiley & Sons, 1906

But the book cannot be downloaded from Google, except for a few snippets! Instead, you can download the whole book from this page:
http://www.archive.org/details/cyanideindustry01munrgoog

The actual URLs for downloading it are:
http://ia331411.us.archive.org/2/items/cyanideindustry01munr... 13.8 Mb or
http://ia331411.us.archive.org/2/items/cyanideindustry01munr... 20.4 Mb

entropy51 - 29-9-2009 at 14:58

But the book cannot be downloaded from Google, except for a few snippets!

You're full of it, JohnWW, or maybe they don't let people in New Zealand have access to dangerous things like chemistry books.

When I click that link there's a button to download PDF, and I did that just now.

Off your meds again?

S.C. Wack - 29-9-2009 at 15:46

That problem and its solution have been discussed time and time again, even in this thread. Like it needs to crawl across the top of the screen in flashing red or something.

Simple heating of ferrocyanide to just below red heat is wasteful of CN, since some nitrogen is lost. Needless to say, the ferrocyanide must be quite white first.

It was just last night that I threw away a shelf near where I had ground dried ferrocyanide on years ago, the blue stains that eventually showed up were still there.

So anyways as some have found, the distillation from H2SO4 is less than theoretical. The addition of CuCl has been recommended - CA 6, 2375 (1912):

A New Method for the Estimation of Ferrocyanides. H.E. WILLIAMS. J. Soc. Chem. Ind. 31, 468-71 [1912] The limitations and errors of the methods in general use are discussed and the following method given: Dissolve 0.5 g. of the ferrocyanide in 100 ml. of water, transfer to a 250-300 ml. distilling flask and add 0.05-0.1 g. of CuCl dissolved in a few drops of HCl, or a sat'd soln of NaCl or KCl; gently shake to mix contents add 25-30 ml. of 4N H2SO4 and distil through a condenser into absorption flasks containing NaOH or KOH. The ferrocyanide is completely decomposed and the HCN distilled off in about 30 mins. gently boiling. The distillate is washed out and titrated in the usual manner with AgNO3 using a few drops of 10% KI soln. as indicator. If desired 25-30 g. of ferrocyanide may be taken, only between 2-3% of its wt. of CuCl being required. Sufficient H2SO4 over that required to form FeSO4 and NaHSO4 must be added. It is advisable to wash the CuCl with a little dil. H2SO4 before using to remove any CuCl2. Sol. or insol. ferrocyanides or those of the heavy metals may be estd. Insol. compds. are finely powdered, transferred to flask and requisite amts. of reagents added. In the case of ferric ferrocyanide Prussian blue etc., more CuCl than that already mentioned should be added. Results reported are practically theoretical even on an experimental scale using 20-25 lbs.

[Edited on 30-9-2009 by S.C. Wack]

JohnWW - 29-9-2009 at 15:54

But the book cannot be downloaded from Google, except for a few snippets!

When I click that link there's a button to download PDF, and I did that just now.

Using Mozilla Firefox 3.52, the latest version, when I load http://books.google.com/books?id=qE4wAAAAMAAJ in the browser, I find that NO such button appears, inviting one to download the book as a PDF. Perhaps Mozilla Firefox cannot load such download buttons? What sort of browser did you use?

I find that most, if not all, books (usually incomplete, even the clearly copyright-expired ones) that Google posts online can be only viewed online as single OCRed pages, the images of which cannot be downloaded, except by screen-capture using something like ScreenThief.

[Edited on 30-9-09 by JohnWW]

entropy51 - 29-9-2009 at 16:45

Your browser may be the problem. I'm using the lame old IE 6.0 something or other. Google won't let you download PDF for anything after 1920 or so, even if copyright is expired, but these old books are available, at least to me. What can I say? Except that I try to always check the links that I post?

entropy51 - 29-9-2009 at 16:57

Quote: Originally posted by S.C. Wack

That problem and its solution have been discussed time and time again, even in this thread. Like it needs to crawl across the top of the screen in flashing red or something.

Those who ignore history.......

That's what happen when threads exceed a few pages.

Thanks for posting the other prep!

crazyboy - 29-9-2009 at 20:19

I am considering a synthesis which may employ small amounts of HCN. Obviously this is an incredibly dangerous and hazardous compound and before I even think of generating such a compound I would like to know if anyone has ever dealt with it and exactly what precautions should be taken.

kmno4 - 29-9-2009 at 21:43

Adding some Cu salt as catalyst of decomposition of ferrocyanide sounds very promissing.
I have a few grams of CuCN so I am going to try it.
I think I will try 25g of K4[Fe(CN)6] and 1g of CuCN.
I have read about decomposition of ferrocyanide with Hg or Mg salts, but Cu is something new for me

BTW.
Sometimes Google Books try cheating by not allowing some books to be downloaded by some IP numbers.
Then you try cheating by changing IP (proxy). In most cases even "useless" Codeen proxies are good for this purpose.

Taoiseach - 29-9-2009 at 22:50

Quote: Originally posted by garage chemist

Ullmanns Encyclopedia says 0,57g/100g in 100% Ethanol at 19,5°C, and 4,91g/100g in Methanol at the same temperature. No other temperatures are given.

I've used Methanol with a Soxhlet extractor to extract KCN from the powdered residue of K4Fe(CN)6 fusion, and the residue from evaporating the MeOH on a boiling water bath in vacuum came out as 85% KCN upon titration with 0,1M AgNO3.

85% purity is less than satisfactory. Any idea what other crap has dissolved in your methanol?

Jor - 30-9-2009 at 00:18

Quote: Originally posted by crazyboy

I am considering a synthesis which may employ small amounts of HCN. Obviously this is an incredibly dangerous and hazardous compound and before I even think of generating such a compound I would like to know if anyone has ever dealt with it and exactly what precautions should be taken.

Fume hood and gloves (absorbed through skin!), or outside. It is dangerous, but not THAT dangerous. The compound is about 3 times as toxic as chlorine, but has bad warning properties (some people cant smell it).
There are much more hazardous gasses like phosgene (10 times more toxic). I have generated quite a lot of HCN, and no problem at all.

woelen - 30-9-2009 at 04:13

I also once had an experiment, which went awry somewhat, the contents of a test tube was bubbling vigorously, giving off pure HCN gas. I lighted the gas and it nicely burnt away, until the vigorous reaction stopped and evolution of gas became too slow to keep the flame. So, this also can be an option if you have to deal with a stream of HCN gas. In the past, this was used as a fiarly safe way to get rid of the gas, which burns to CO2, H2O and N2.

kmno4 - 30-9-2009 at 23:19

I have just tested this "Cu method".
Effect is the same as without Cu

Maybe is works on high dilutions and large excess of acid.
Volume ~130 ml, 0,5g K4..... and ~48-fold mole excess of H2SO4 is not interesting for me. On this proportions it woks also without any Cu salt, as it is described in previously cited paper from JChemSoc.

entropy51 - 1-10-2009 at 05:12

Quote: Originally posted by kmno4

I have just tested this "Cu method".
Effect is the same as without Cu

Without a catalyst only part of the ferrocyanide is converted to HCN. A few percent by weight of CuCl increases the yield of HCN considerably for me. How did you determine that the effect was the same as without Cu? It doesn't require a huge excess of H2SO4. See the patent I posted in the References Wanted thread about a week ago.

kmno4 - 1-10-2009 at 07:47

A few percent by weight of CuCl increases the yield of HCN considerably for me. How did you determine that the effect was the same as without Cu?

I determined it by weight, comparing (by amount of prepared NaCN) with no-Cu methode described earlier by me.
But what you mean by "considerably" ?
How much of KCN or NaCN can you get from, for example, 100g of anhydrous K4[Fe(CN)6] ? Just recalculate it accordingly to amount of K4... used by you.
BTW. I have found paper about cyanate/cyanide conversion:
J. Am. Chem. Soc., 1918, 40 (3), pp 482–489.
The most important conclusion from reading it: cyanides are really powerfull reductants

ps. I read mentioned patent but I cannot find amounts of chemicals needed to convert given amount of K4.. to HCN. Some amounts are given but with no sense for me.

ps2
Funny thing. I discovered that CuCN I put in flask (with H2SO4, K4.. and H2O) reminded undissolved

.
Maybe CuCN is not catalyst, but some chloride salts ?
I will try with CuCl, but I have to prepare it first

[Edited on 1-10-2009 by kmno4]

entropy51 - 1-10-2009 at 11:31

Did you use enough H2SO4? Without Cu you need 1.5 mol H2SO4 per mol of ferrocyanide. With Cu catalyst you need 5 mol H2SO4 per mol of Ferrocyanide. If the H2SO4 is your limiting reagent, adding catalyst won't increase the yield. That's the reason for the stoichiometry used in the patent.

Have you ever tried to titrate your NaCN product? Just to see how pure it is?

Seems like the Cu would need to be in solution to work, doesn't it?

kmno4 - 1-10-2009 at 12:15

Patents are very bad source of knowledge, in most cases.
I took 25g of K4[Fe(CN)6], 52g of 96% H2SO4, ~160g of H2O and 0,7g of CuCN (small granules, 1-2 mm).
After 5-hours heating (boiling) I still had lots of light green shit in a flask.
After cooling I removed green slury from flask and then noticed granules of CuCN on the bottom. It seem that CuCN is not soluble in this mixture on boliling. It would be good if someone else confirmed (or not) this observation.
Yield of NaCN: ~6g. A few grams remain in ethanolic/water solution (~200 ml) . So it is close to 50% recovery of cyanide from ferrocyanide.
Purity: unknown, probably very high because it works as it should work. I have to buy at last some standard sol. of AgNO3 to confirm this purity.

entropy51 - 1-10-2009 at 12:27

Quote:

It seem that CuCN is not soluble in this mixture on boliling.

CuCN is not soluble in most aqueous, not even acids (up to a point). It dissoves in aqueous NaCN.

kmno4 - 1-10-2009 at 22:48

So maybe CuCN is not a catalyst (as patent states) in this reaction. Besides it is hard to imagine how any Cu salt can act for ferrocyanide decomposition in H2SO4.
But if CuCl really works catalytically, then real catalyst can be HCl. It sounds stupid, but....

Jor - 2-10-2009 at 02:29

I wonder if dilute HCl also works in place of H2SO4, as some H2SO4 tends to oxidise the cyanide. Indeed you wouldn't want the HCl to run in your EtOH/KOH, but at low concentration, water evaporates and not HCl, until the azeotrope is reached.

entropy51 - 2-10-2009 at 05:20

Quote: Originally posted by kmno4

So maybe CuCN is not a catalyst (as patent states) in this reaction. Besides it is hard to imagine how any Cu salt can act for ferrocyanide decomposition in H2SO4.
But if CuCl really works catalytically, then real catalyst can be HCl. It sounds stupid, but....

I think the Cu salt needs to be in solution. I dissolved the CuCl in a minimal amount of HCl before adding it, which is what Williams describes in the article quoted by S.C. Wack above. For me, CuCl gave over a 50% increase in HCN, determined by titration. I did not try to isolate the NaCN - I have enough of that for the time being.

kmno4 - 2-10-2009 at 17:10