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Author: Subject: Preparation of cyanides
Nick F
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[*] posted on 27-10-2002 at 14:55


I'm glad you got it to work! It means I can copy you and avoid all the frustrating failures!! :)
I'd love a good way to make cyanides, and now it seems there is one, although I'll be making my cyanates with urea.
There are a few things I'd like to try with cyanides, mainly the production of 1H-5H tetrazole with NaN3 and NaCN (rather than 5-R tetrazoles made with nitriles), also cyanides as fuels (especially amine cyanides in gas generating compositions), and silver/copper (etc.) cyanide oxosalts as energetic materials.

For determining cyanide content, maybe you could find a metal cyanide that is insoluble with water, probably lead or silver cyanide would be. Dissolve a known weight of your product in water, add excess Pb(NO3)2 or AgNO3 or whatever, collect the ppte, dry and weigh. You work out the number of moles of ppte, and you therefore know the number of moles of cyanide in your initial sample, and from there it's easy to work out the purity.
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[*] posted on 27-10-2002 at 14:56


Damn, I forgot hydroxides, carbonates etc will probably also ppte :(
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[*] posted on 27-10-2002 at 15:18


I haven't yet come up with a good method of analysis. I should pay a visit to the library, but I've been busy. One idea that comes to mind is precipitating any carbonate with calcium or barium nitrate, then precipitating cyanide with silver nitrate. I'm quite sure there are no significant amounts of hydroxides in my solution. Unless I work with large quantities, though, I won't have very much accuracy in my work. My electronic balance is sensitive only to 0.1 g. That's fine for most of the stuff I do, but terrible for analysis.

Anyway, I'd like to hear about it when/if you get around to making cyanides starting from urea. I was going to try that myself as a followup to the cyanuric acid method, but I have been trying to be good and do some homework this afternoon.
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[*] posted on 27-10-2002 at 17:24
Another tip


I stained some of my glassware with prussian blue while doing cyanide tests. Conc. HCl didn't seem to have any effect on it. Dilute HF took it off like a charm, though, and didn't harm the glass either.

And speaking of cyanide tests, here's an extremely simple way of obtaining the mixture of Fe(II) and Fe(III) salts you need to precipitate cyanide as prussian blue:

Dissolve copper (II) sulfate in water. Add an excess of steel wool or iron powder, so that you are left with a mixture of iron (II) sulfate, metallic copper, and metallic iron. Filter to remove metal bits. Keep the iron (II) sulfate solution stored well protected from the air, since it's easily oxidized to iron (III) sulfate. In fact, that's how it's used in the cyanide test.

Mix a bit of the green iron (II) sulfate solution with a sample of your suspected cyanide. You may need to acidify it, too, with a little HCl or similar (obviously you need to limit the amount of suspected cyanide you test because of this step!) Swirl the liquid around to agitate it and expose it to the air. If there's cyanide in there, the liquid will take on a beautiful shade of blue (and/or precipitate blue particles) as the iron (II) sulfate is oxidized by the oxygen in the air.

I'm sure you can also prepare iron (II) sulfate from iron and sulfuric acid, but CuSO4 is safer and easier to work with and clean up. Also, the CuSO4-iron reaction is quickly completed, whereas you can wait days for the last traces of acid to finish reacting when you just mix an acid with an excess of metal.
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Nick F
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[*] posted on 29-10-2002 at 04:44


Polverone, I posted my results in your thread on the E&W. They're quite promising.
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[*] posted on 29-10-2002 at 14:25


I think I read somewhere that the discoverer of HCN, Scheele, later used ammonium chloride when preparing potassium ferrocyanide, insted of dried blood and animal hides. Maybe it's one way to go?
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[*] posted on 29-10-2002 at 15:37


Nick, could you post your results here as well? :)



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[*] posted on 29-10-2002 at 16:21


Quote:
I think I read somewhere that the discoverer of HCN, Scheele, later used ammonium chloride when preparing potassium ferrocyanide, insted of dried blood and animal hides. Maybe it's one way to go?


I don't see how ammonium chloride could be directly substituted. If you heat ammonium chloride with a metallic base, you're going to end up with a metallic chloride. Was it some other ammonium salt that you were thinking of?

And, yes (to Nick F.), it would be nice to see that message that you posted to E&W, as it seems that roguesci.org is taking an extended leave of absence...
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[*] posted on 30-10-2002 at 05:20


Oh yes, sorry I forgot access has been restricted... here it is:

16g of urea, 16g of NaHCO3 and 5g of charcoal were ball milled for half an hour, to form an intimately mixed dark grey powder.
The mixture was heated on an oil bath at around 150*C with stirring until the reaction had stopped (lots of ammonia is given off, so do it outside!), as indicated by the effervescence susbsiding. The pasty mixture was stirred as it cooled to break it up.
The black, gravel-like substance remaining was put into an iron crucible with a narrow neck (used to be a CO2 canister), and placed in a very hot (bright yellow) fire. I used a coal fire, fed with air at about 400*C from a paint stripping gun. After a short amount of time a flammable gas was produced (CO), and heating was stopped 10 minutes after this gas was no longer produced. Charcoal was poured into the crucible, which was then left to cool, with the charcoal hopefully excluding most air.

The residue was extracted with cold water and filtered, leaving a clear, colourless, strongly alkaline solution. A drop put into citric acid solution produces HCN smell :)
I've made some CuSO4, so I'll do the prussian blue test too.

(I haven't got round to doing the prussian blue test yet...)
So it would appear that it has worked, but I have no way of doing a quantitative analysis :(
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[*] posted on 30-10-2002 at 09:23


It certainly sounds like you've encountered success too. Try to dry yours a little faster than I've done with mine. I've left mine at room temperature for days, and I fear that when it's finally dry I'll mostly have sodium carbonate just from atmospheric CO2. I'm going to have make another batch, I think. On the other hand, the Kirk-Othmer Encyclopedia says that above 50 degrees C, NaCN solutions undergo some irreversible conversion to formate and ammonia. So I have to be careful to use gentle heating if I want accelerated drying in the future.

P.S.: It's not just that E&W has gotten more restrictive in who's allowed in. I still have my account and everything. It's just that for three days now I've been getting the message "Rogue Science is closed for October 28" and a prompt for a username/password. My usual name/pw combo doesn't work, either.
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[*] posted on 31-10-2002 at 01:34


That's what I meant by restricted, only staff have access at the moment.

My NaCN solution has also been sitting around for a while now, I'll do another batch and vac. dry it straight away.
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[*] posted on 31-10-2002 at 01:58
E&W


Be careful and open you eyes ! :cool:
Are you sure the mirrored E&W forum
was (are) not a place to isolate people by lousy
law-hunters and this sort of lackeys ?
:P




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[*] posted on 31-1-2003 at 21:32
interesting!


How would one synthesise or purchase cyanuric acid?
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[*] posted on 14-2-2003 at 23:59


I say purchase it. Today I went to the HomeDepo which is a pretty big hardware store and checked out the pool chemicals section, I had found cyanuric acid, I forgot what I said its used for. Never brought it though because I was short on money and time. From what I remember I think its in 1 pound (454 gram) bottles. The cost is around $15 pretty cheap.Is it possable to prepear cyanides with cyanuric acid?



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Polverone
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[*] posted on 15-2-2003 at 10:56


Yes, it is used to protect swimming pool chlorination agents from photodegradation, IIRC. And yes, it can be used to prepare cyanides - see earlier in this thread. Sorry Ramiel, I would have answered much sooner but I hadn't noticed your question. I am glad someone did.
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[*] posted on 30-3-2003 at 12:10
I read above


that someone tried to ppt. the Fe2+ from the Na Ferrocyanide by the addition of Na2S. I for some reason (which I can't quite conceptually explain) think NH4OH will probably ppt the Fe2+ out of soln. Leaving a mix of NaCN, NH4CN. Now X-# of moles of NaOH are added (X = # of moles of NH4+). This theoretically should leave quite pure NaCN.

[Edited on 30-3-2003 by Boob Raider]




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[*] posted on 31-3-2003 at 19:17
I also found


out that Na ferrocyanide decomposes at ~ 485*C to NaCN, Fe, C and N2. But a lot of CN- is lost as C and N2, although it is a way around HCN and NaCN obtained can very easily be purified.



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wink.gif posted on 18-6-2003 at 04:07
Making cyanides


You can make cyanides just by mixing an alkali or an alkali-eart carbonate, carbon and heating that strongly on air (no reducing atmospere needed)
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[*] posted on 1-7-2003 at 07:16


The original quote:
"Cyanides.—The salts of this acid, known as cyanides, may be prepared by the action of cyanogen or of gaseous hydrocyanic acid on a metal; by heating the carbonates or hydrooxides of the alkali metals in a current of hydrocyanic acid; by heating alkaline carbonates with carbon in the presence of free nitrogen: BaCOI + 4C + N2= Ba(NC)i+ 3C0;"
This may be useful as well:
"Ammonium cyanide, NH4NC, a white solid found to some slight extent in illuminating gas, is easily soluble in water and alcohol, and is very poisonous. Its vapour is inflammable. It is obtained by passing ammonia gas over hot coal; by subliming a mixture of ammonium chloride and potassium cyanide; by passing a mixture of ammonia gas and chloroform vapour through a red hot tube; and by heating a mixture of ammonia and carbon monoxide:
CO+2NH3=NH4NC+H2O."
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Polverone
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[*] posted on 1-7-2003 at 11:14
"heating strongly" is putting it mildly


Before I used the cyanate method I tried heating powdered charcoal with barium carbonate in air. I got the container to glow a nice cherry red and held it there for 20 minutes, but after the mix had cooled I couldn't find even a trace of cyanide.
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[*] posted on 1-7-2003 at 13:42


Well, the reaction between Chloroform and Ammonia is a well-known way to produce Hydrogen Cyanide...

NH3 + CHCl3 --> HCN + 3 HCl

If you don't mind working with straight HCN, then this seems like a feasible route. At least, it would be for me, since I have fairly easy access to Ammonia Gas and Chloroform...

The only trouble would be separating the HCl.
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thumbup.gif posted on 3-7-2003 at 04:41
NH4CN


How about the ammonia-coal route?
I think NH4CN is convertible into alkali-metal cyanides by passing it through an alkali-metal hydroxide.:o
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[*] posted on 7-7-2003 at 07:58


I'll try tht.The coal/ammonia thing.Recomend any tests?
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thumbup.gif posted on 8-7-2003 at 06:41


Yes, (quote)
"One of the oldest, simplest, and best
qualitative tests is the Prussian blue test.
This test combines the unknown with a mixture of iron (II) and iron (III) salts in acidic media. The formation of a blue solution or precipitate indicates the presence of cyanide."
I add myself: Fe(II) and especially Fe(III) salts undergo strong hydrolysis, so
they're already self-acidified.:cool:
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[*] posted on 8-7-2003 at 07:52


I guess I forgot to mention that I have next to nothing.How about trying to make copper cyanid?

Another thing.When you say ammonia you mean ammoina /water or the gas?
Edit:
I sucesfully made some sodium cyanide and ran an old fashion gold test(suposed to get paid for it).200 samples(all negative,btw).

The sodium cyanide was prepared by heating with sodium carbonate and urea.After crushing the suspected ore I added water/NaCN to exces(first few times anyway).After about 1 minutes of stiring I filtered out the rock/crap/whatever.

Now I know activated carbon would have been better for this case but all I had was ion exchange resin.No precipitate was observed in any of them.Just for the hell of it I actually used this with a few spec of gold(no not mine)and precipites were observed.

Just tought you might want this and I'm sorry I dont hav better detrails.Just got it from some prospcters guide.

[Edited on 9-7-2003 by Iv4]
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