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Author: Subject: Preparation of cyanides
woelen
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[*] posted on 11-5-2009 at 22:43


I am working fairly comfortably with solutions of KCN. Yesterday I did an experiment with nickel/cyanide complexes (see other thread over here at sciencemadness) and occasionally I do other experiments with cyanide. I always use very small amounts (e.g. 200 mg or so) and keep solutions alkaline. I ALWAYS keep the container of KCN closed. I take out a small amount for the experiment and immediately close it again. This is important, because KCN is hygroscopic and easily absorbs water from air, which leads to formation of HCN and KOH (and K2CO3 in a secondary process by uptake of CO2 from air).

After the experiments, I pour the cyanide solutions in concentrated household bleach. This waste then slowly produces gas (nitrogen) and the cyanide is destroyed within a few minutes. If the waste is free from heavy metals, then it even can go down the drain, because all cyanide is destroyed and it is not more dangerous than bleach.

Working with HCN is something which I don't do in my lab. I have no real fume hood and having HCN around does not feel comfortable.




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Mossydie
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[*] posted on 15-5-2009 at 15:31


Someone told me that heating superglue gave off cyanide, although he was about 60 so I would expect they use safer superglue compounds by now.
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[*] posted on 26-5-2009 at 20:04


Well I know that superglue is cyanoacrylate, and it's remained that way for quite a hole. But the energy required to break off that cyanide is quite high, so i doubt it would be possible.
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[*] posted on 4-6-2009 at 04:04


First post here, hello. I read all 10 pages of it, and I have the question: HNO3 is a stronger acid than H2SO4, but the latter is not availbable in my country. However on stronger oxidation of potassium ferrocyanide, what will be the products?
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entropy51
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[*] posted on 4-6-2009 at 14:50


Generally oxidizing agents such as HNO3 convert ferrocyanide to ferricyanide, and sometimes to nitroferrocyanides, and even further to carbon monoxide.

See Williams' Chemistry of the Cyanogen Compounds, page 88-89.

http://books.google.com/books?id=vW86AAAAMAAJ&pg=PA84&am...
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[*] posted on 6-6-2009 at 14:08


Quote: Originally posted by jmneissa  
Okay so I have read around about cyanide's and all there uses in the lab but where ever I look I always see all the warning about how poisonous and dangerous it is. But the MSDS sheets for everything always over exaggerate the unhealthiness of everything. I wanted to know your guys honest opinion on how dangerous cyanide is and is it something that a amateur chemist should be messing with even if all the proper safety precautions are taken?


I'd be more worried about the explosion hazard. HCN is as inflammable as hell, just about any oxidizer will set it off, and it can even self-detonate (by polymerization).

Quote:
The 1-minute inhalation LC(50) in dogs is 616 mg/m(3); in rats and mice, the 5-minute inhalation LC(50) values are 484 ppm and 323 ppm, respectively [Sax and Lewis 1989]. The oral LD(50) in the mouse is 3.7 mg/kg [Sax and Lewis 1989].

-- OSHA


You can find much more toxic stuff being discussed and experimented with in other forums. In another thread, one poster was making ketene and that idgit was actually sniffing to see if he'd made it. The LC(50) is way lower for that than it is for HCN.

Don't take anything you see on the Net as Gospel. Do your own research.

Be very certain you know what you're doing, and if you have any doubts, don't do it.

Use common sense. Having to explain yourself to Fire Marshalls and insurance adjusters isn't a whole lot of fun.
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[*] posted on 6-6-2009 at 19:12


Quote: Originally posted by KnooBill  
First post here, hello. I read all 10 pages of it, and I have the question: HNO3 is a stronger acid than H2SO4, but the latter is not availbable in my country. However on stronger oxidation of potassium ferrocyanide, what will be the products?


Oxidizers (like Cl2, Br2, KMnO4, H2O2) will convert potassium ferrocyanide to ferricyanide according to Beilstein, citing Brodie, Pogg. Ann. 120, 302; Weltzien, Lieb. Ann. 138, 142. Warming with HNO3 gets the red salt also, and then nitroferrocyanic acid. It can be a bit tricky though according to Weltzien, Lieb. Ann. 136, 166 H2O2 will lead the ferro salt to ferri, but the ferri compound is reduced by H2O2 to the ferro salt! Using an excess of Cl2 will convert the ferrocyanide to Berlin Green (Beilstein).

I used conc. H2O2 before against an alkali ferrocyanide. I wasn't able to isolate ferricyanide because I likely added too much conc. H2O2 and let it sit a long time outside (few days), ending up with a pitch dark blackish-green solution. Although sodium and potassium ferricyanide are red, at least the latter's solutions are also known to be olive-green in color, but I'm not so sure it should be this dark, this must be the ferric ferricyanide compound, Fe3(CN)8.4H2O, "Berlin Green").

[Edited on 7-6-2009 by Formatik]
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[*] posted on 8-6-2009 at 14:31


I really want to make more KCN, as I only have a few grams and it's very interesting stuff, especially to make complexes.

Today I tried to make some KCN. I used the method of leading HCN ethanolic KOH. I always tried to avoid this route, but I decided it is really the best and cleanest method. I took safety precautrions:
Fume hood (I tuned the motor to speed 2, I usually use 1), lab coat, think latex gloves and goggles.


3,5 grams of potassium ferrocyanide were put in a erlenmeyer, together with 30mL of 3-3,5M H2SO4. A tube adapter was connected, followed by a plastic tube leading to another glas tube (the ones you do in gas wash bottles), and this was lead into the ethanolic KOH. It was put at the surface, if suckback would occur, it couldn't reach the HCN generator). To prepare this, 3,5 grams of KOH were added to 40-45mL of absolute ethanol and stirred. Not all dissolved. The insoluble material was K2CO3 as it fizzed when 2M HCl was added after deacnting the ethanolic KOH.

I turned on the hot plate, stirred both solution with magnetic stirring (I have 2 ;) ) and there was a slow gas evolution, but no bubbles. It seemed that no bubbles were formed as all HCN instantly dissolved at the tip of the tube . After 10 minutes I closed the sash and I went watching TV. Nothing could go wrong, as would suckback occur (wich is not possible as long as the heat is on) the ethanol would not be able to get in the flask.
After one and a half hour (23:00) I came back (I came checking the experiment a few times for few secs to control if nothing went wrong) . Some white precitipate had formed but very little. The reaction flask was green, because there was a green precitipate (???) .

I was puzzled and quite pissed off, as I though it failed and I have only a few grams ferrocyanide left. I stopped the experiment. I started cleaning everything up. The very little precitipate formed was not compact and it was very hard to decant. I didn't bother setting up a filter and such for maybe 100-200mg of product.
I put all solutions and rinses in a large beaker and made alkaline with 10% NaOH. Next bleach was added, and I will dispose of it tomorrow.

SO what did I do wrong? Should I just keep heating for a much longer time? Did I overheat? The temperature was around 80-90C all the time, one time even 100C. I'm quite surprised it didn't work.

Any tips?

[Edited on 8-6-2009 by Jor]

[Edited on 8-6-2009 by Jor]
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[*] posted on 9-6-2009 at 01:35


"The temperature was around 80-90C all the time, one time even 100C"
Temperature of what ? Solution should be heated up to boiling.
In r.t. or even warmer, reaction is very slow.
Green precipitate (FeK2[Fe(CN)6]), turning blue on air is normal thing. It very, really very slowly reacts with H2SO4 even on boiling.
You should get about 1,5-1,7 g of dry KCN from 3,5 g of (anhydrous) k4ferrocyanide. Probably you will not be able to decant alcohol from KCN beacuse it formes gelly suspensions (but easily filterable).

[Edited on 9-6-2009 by kmno4]
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[*] posted on 11-6-2009 at 06:02


Looks as if it will not work with HNO3, and from my chemical knowledge and a fast read of the H2SO4 proccess (the one at the top of Chemistry in General) it is too difficult to try to produce any. If I recall correctly KMnO4 mentioned it could work with H3PO4, however I do not know whether it is obtainable or not. That's the thing that I put at first priority now.
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[*] posted on 11-6-2009 at 12:14


You should use H2SO4 of somewhat higher concentration and the temperature then should not be too high (60 C or so, not more). This reaction, however, is not clean at all. You get side-reactions, such as making (CN)2 and even CO, due to partial oxidation of the cyanide ligands. You need careful control of the reaction conditions.

Jor, if you are running out of ferro/ferri cyanides, there is an almost unlimited supply in Germany from many eBay suppliers (search for "blutlaugensalz"). Just one example:

http://cgi.ebay.de/1Set-Blutlaugensalz-rot-u-gelb-jeweils-20...

But there are plenty of sellers. This is my preferred source for both potassium ferrocyanide and potassium ferricyanide. I use both chemicals quite a few times, also for fun experiments with the kids and for photography toner processes and I already purchased new samples from Germany a few times.

Another source in Germany, which sells chemicals for crystal growing:
http://www.crystalgrowing.com/index_d.htm
Click the "chemikalien" link at the left. Very cheap red and yellow prussiate of potash, 500 grams for only EUR 12.90. Also a few other possibly interesting chemicals. Guarantees for delivery are only given for EU citizens!

Ordering ferricyanides or ferrocyanides is not suspicious at all, despite the fact that cyanide ligand is contained in the chemicals. These are common chemicals in photography and other old art processes.




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[*] posted on 11-6-2009 at 13:18


According to an article posted on this board, H2SO4.16H2O to H2SO4.18H2O is ideal concentration giving quite clean HCN.
Roughly, this is 3.0-3.5M right?

Are HCN , or cyanide solutions in general (either in water or ethanol) absorbed throught the skin? That might be a good thing to know. I long wore latex gloves just in case, but is this necessary? Or aren't these suitable?

Thank you woelen for the sources. Especially the crystalgrowing site is very interesting. A bit too large quantities for my taste but there are some pretty interesting chems. Sodium bromate (I have potassium bromate, but this is quite insoluble) and nickel sulfate. The latter is quite expensive at most sources but here it is very cheap.
Are these chemicals pure? I guess they would need to be, as it a requirement to form very nice crystals AFAIK, but I;m not sure.

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[*] posted on 16-6-2009 at 01:35


Quote: Originally posted by Jor  
Are HCN , or cyanide solutions in general (either in water or ethanol) absorbed throught the skin? That might be a good thing to know.


Yes and yes. Remember: Google is your friend.
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[*] posted on 22-9-2009 at 03:03
KCN


KCN

Thank you to you all for the info on this board, it has been a great help in understanding what to do safely (or almost safely :) )

I am interested in making KCN preferably with Potassium Ferricyanide and H2SO4, which I can buy, as it seems much cleaner than Ferrocyanide. Just a few grams is all that is needed for further experiments. (No I don't want to kill myself. I am a Medical Doctor and can do that in many more simpler ways).

I am obsessed with purity so bubbling HCN through a solution of absolute (95%) ethanol and KOH, filtering under vacuum then drying under Vacuum and CaCl2 at rt seems the way forward. Unfortunately I can find little/no information on this. Everyone seems to use ferro in a tin can which seems to me bound to be impure but good enough for most purposes I suppose.

My set up would be outdoors wearing a Hazmat suit and SCBA (no fume cupboard) which I can 'borrow' from a friend at work who does virology. First injecting chilled H2SO4 into a 2L RBF then immediately sealing it with a rubber bung with a thermometer though it and then heating to 60 C in a water bath via a gas burner. This would be connected to a Liebig condenser feeding through a water trap into another much smaller RBF containing ethanolic KOH in an ice bath with the outlet connected to a long hose pointing down wind and possibly into a concentrated bleach bath. I am not sure about adding a vacuum aspirator as it would involve yet more connections and leaks even sealed with silicon grease.

This seems relatively safe and the area is quite isolated. But I have no idea of the amounts or reagents required to make say 4g. I have been away from a lab for a few years now and expect things to go wrong and have a bad yield :(.

I can source lab grade Ferricyanide, 95% ethanol, KOH pellets, and amazingly 98% Sulphuric acid (but no lower concentration).

I am not good at working out the dilutions to get this to work and from what I have read its not simple. Despite extensive searching I cannot find any instructions on the net so here I am begging for help. Any feedback as to the proposed set-up and amounts/concentrations of the reagents would be much appreciated.
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[*] posted on 22-9-2009 at 05:45


WTF! A medical doctor that can't work out simple dilutions? I can do it but I am nowhere close to the skill level of a doctor or a practicing nurse for that matter. Why don't kill the bullshit and tell us what is the REAL story.



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entropy51
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[*] posted on 22-9-2009 at 05:59


He's asking for a KCN recipe on his first post, and his bio is confused, to say the least.

Quote:
Did Chemistry, Physics and Biology A levels. Wanted to go on to do Chemistry but was dissuaded so did a BSc in Cellular and molecular Biology instead. Qualified as a Doctor and have since done various jobs including a lot of Histopathology lab work (which involved handling some pretty hazardous stuff). So I am comfortable around a lab and working with potentially potentially things. I know a lot about cellular chemistry but not much general chemistry especially physical. I have never lost my interest in chemistry but I never had the time to do any, now I have. As you can see I am a rank beginner so please give me a break and don't flame me if I ask something stupid or elementary.
He describes training and experience, then says he's a rank beginner.
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[*] posted on 22-9-2009 at 06:39


kewl or terrorist? Also, note he did not read the thread since most if not all his questions are already answered. Quite suspicious I am.

@moderators- Crazy idea but it just might protect the forum. How about password protection for certain informative threads? More specifically this one on cyanides. I realize the argument that every exploration in chemistry has the potential for harm but this forum being in the news for teaching would be terrorists to make cyanide gas bombs is not the publicity we want. So far, what little media coverage I have seen regarding Science madness has been in a positive light. Lets keep it that way. I suggest after 25 posts that contribute to the development of this forum should qualify for a password.

[Edited on 9/22/2009 by chloric1]




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[*] posted on 22-9-2009 at 08:21



Table salt is packed with Sodium Hexacyanoferrate II as an anti caking agent (to stop you making cakes I presume :P). What percentage is used?

EDIT:
Perhaps this:
http://research.transportation.org/sites/research/docs/tsran...
answers my question.

Dann2

[Edited on 22-9-2009 by dann2]
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[*] posted on 22-9-2009 at 08:32


It is a very small percentage I think dann2 - not a useable amount.




(And what a nasty & paranoid welcome for someone who writes a very sensible first message :( - Fear and mis-trust clouds the senses)
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chloric1
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[*] posted on 22-9-2009 at 12:39


Distrust in good measure sonogashira. His first post was asking about making KCN and he seems very inconsistant. He is a docotr but unalbe to figure something as simple as dilutions. This forum is about GIVE and take and about taking some steps on your own. Its only fair since many members here figure out how to prepare hard to get reagents by the sweat of there brow and using there own pocket books.

Furthermore, Sciencemadness is one of the longest running and most usefull resource for the home chemist online and we must be diligent to protect its integrety. I welcom our newest guess but wish he would be upfront with his intentions.




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entropy51
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[*] posted on 22-9-2009 at 13:55


Sonogashira, don't you find it a little odd that someone wants to begin their new chemistry hobby by making KCN?

And that someone who says he is "comfortable around the lab" apparently can't do simple chemical calculations?

And that someone says they want to make 4 grams but plans to use a 2 liter flask???

I wouldn't convict him based on these things, but I wouldn't help him either. As chloric1 said, the information is already posted for anyone knowlegeable enough to attempt making HCN. If they need further help, they probably shouldn't try it.

[Edited on 22-9-2009 by entropy51]
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[*] posted on 22-9-2009 at 14:34


The name "Sakamura" sounds Japanese, like "Sonogashira"; but his talking about "A Levels" suggests that he is in the UK, not Japan. He had better not let Scotland Yard or MI5 know about his intentions!
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[*] posted on 22-9-2009 at 14:38


Quote: Originally posted by JohnWW  
He had better not let Scotland Yard or MI5 know about his intentions!
I assume they know everything posted here, don't you?
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[*] posted on 22-9-2009 at 17:49
Wow


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]
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[*] posted on 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.




The single most important condition for a successful synthesis is good mixing - Nicodem
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