Sciencemadness Discussion Board

Preparation of cyanides

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Eclectic - 15-5-2007 at 16:43

Does the same reaction work with sodium ferrocyanide and sodium carbonate or hydroxide? You might be able to get ferricyanide from
iron reduction of cyanate (brake turnings). References?

Definitely a MAD science project. :D

You can't get much cheaper starting materials than sodium bicarbonate, urea, and brake turnings.

[Edited on 5-15-2007 by Eclectic]

garage chemist - 15-5-2007 at 17:01

What do you mean by brake turnings? Iron turnings?

The melting of ferrocyanide with carbonate to decompose the complex does only work with potassium salts as far as I know, due to their much lower melting point.

Also, I cant get sodium ferrocyanide, only the K salt which costs something like 26€ a kg. A kg will make a huge amount of HCn though.
I'll probably try out the NaOCN + C process first, and if it doesnt give enough HCN to be worthwhile, I'll purchase K-ferrocyanide and K2CO3, which is pretty much guaranteed to work.

evil_lurker - 15-5-2007 at 17:07

Use isopropyl nitrite to turn acetone into oximinoacetone, degraded with heat and catalyzed by triphenylphosphine into HCN, acetyl chloride, or molecular sieves.

http://www.google.com/patents?vid=USPAT3307905&id=5FxLAA...

http://www.google.com/patents?id=A6RXAAAAEBAJ&printsec=a...

Overall it seems like a fairly straightforward reaction... all thats needed is sodium nitrite, sulfuric acid, acetone, and a catalyst and perhaps some carboxylic acid as a solvent.

[Edited on 15-5-2007 by evil_lurker]

Eclectic - 15-5-2007 at 19:39

When automobile service shops turn brake rotors and drums they end up with a lot of cast iron/steel turnings in little flakes, spirals with a lot of surface area. You can probably get them for free.

I'm thinking reducing a sodium or potassium cyanate melt with iron turnings will make ferrocyanide.

garage chemist - 15-5-2007 at 23:08

If iron reacts appreciably with NaOCN at the temperature at which reduction by carbon takes place, it would be bad news as I want to use a soup can as the crucible.

[Edited on 16-5-2007 by garage chemist]

kmno4 - 16-5-2007 at 06:17

Quote:
K(Na)OCN + C


As I see it is neverending story, because of its ostensible simplicity, I think. If you cannot reach about 1000 C - just forget about good (> 50%) yield. If heating is prolongated - KCN will oxidate to KOCN and ->.....-> K2CO3.
From some book:
Take 160g K4[Fe(CN)6] + 60g K2CO3 + 6g C and melt as long as all gases (CO) will go away. Extraction with 60% EtOH gives 80-100g KCN.
Much simpler version: heat (>700 C) K4[Fe(CN)6] in almost closed vessel (to prevent oxidation). Melt contais only KCN, traces K2CO3, Fe and iron carbide (I forget formula). Nor K2CO3 nor KOCN reduction is needed.
To both variants the best is resistance furnace.

Good luck(yield) and do not kill yourself ;)

[Edited on 16-5-2007 by kmno4]

Eclectic - 16-5-2007 at 08:47

Muspratt, Vol. II, page 451 gives a preparation of potassium ferrocyanide. Nitrogen rich materials (blood, hooves,etc.) fused with carbonate of potassia in iron vessels at red heat. Resulting grey mass, lixivated with boiling water and concentrated yields yellow prussate of potassia. See also the very first post in this thread, and page 3...

A cheap lidded cast iron dutch oven might hold up to the red heat better than a thin steel can, and do a better job of keeping out oxygen.

Dutch Ovens

[Edited on 5-16-2007 by Eclectic]

Axt - 23-5-2007 at 11:27

Quote:
Originally posted by evil_lurker
Use isopropyl nitrite to turn acetone into oximinoacetone,


Do you have reference to that reaction? I have the attached article, which uses the less then convenient gases; methyl nitrite and HCl. Did u you just assume isopropyl nitrite due to analogy or have you seen it documented?

[Edited on 24-5-2007 by Axt]

Attachment: Experiments on the preparation of oximino-derivatives - J. Chem. Soc., Trans., 1920, 117, 587 - 590.pdf (239kB)
This file has been downloaded 1261 times

evil_lurker - 23-5-2007 at 12:32

Well according to this patent, it works.

http://www.google.com/patents?id=cB9IAAAAEBAJ&printsec=a...

To a stirred solution of 465 grams of acetone and 5 milliliters of concentrated hydrochloric acid cooled in an ice bath, 178.4 grams of isopropyl nitrite was added dropwise. When the addition was completed, the isopropyl alcohol formed and the unreacted acetone were removed from the product under reduced pressure. Oximinoacetone weighing 164g (94% conversion, nitrite basis) with a melting point of 61-64ºC was obtained. Recrystallization from an ether-petroleum ether mixture yielded white crystalline oximinoacetone having a melting point of 64.5-65ºC.

In the foregoing example, the hydrochloric acid-nitrite weight ratio was 0.030:1 and the acetone-nitrite mole ratio was 4:1.

Isopropyl nitrite is rather easily obtained by this:

http://www.orgsynth.org/orgsyn/prep.asp?prep=cv2p0108

http://www.orgsynth.org/orgsyn/prep.asp?prep=cv3p0191

A mixture of 147 g. (80 ml., 1.5 moles) of concentrated sulfuric acid (sp. gr. 1.84), 60 ml. of water, and 180 g. (230 ml., 3 moles) of 97% isopropyl alcohol, previously cooled to 0°, is added to a solution of 227.7 g. (3.3 moles) of 97% sodium nitrite in 1 l. of water, cooled to −5°. About 2 hours is required for the addition of the alcohol solution, during which time the temperature of the reaction mixture is maintained at −2° to 0°. The product may be isolated and purified as described under butyl nitrite. After drying over 15–20 g. of anhydrous sodium sulfate, the nitrite is distilled from a steam bath using a 20-cm. column. Practically all the isopropyl nitrite distils at 39–40°/745 mm. as a pale yellow oil; the yield of product is 191 g. (71.4%). Isopropyl nitrite, when stored in a refrigerator, has been found to be much more stable than butyl nitrite.

The catch for making HCN is a decomposition catalyst to which triphenylphosphine works wonders with yields as high as 95% based up on the oximinoacetone.

http://www.google.com/patents?id=A6RXAAAAEBAJ&printsec=a...

Organikum - 23-5-2007 at 18:59

I can buy diethylether in the drogerie by the liter - no questions asked. And formic acic. And acetic acid. Except "One or more liters?" Because they have to fetch them from behind and dont want to go twice.
I cannot buy methylalcohol though as its a "poison". Funny. But red phosphosphorus by the kilo. They have no smaller batches.

Funny world

[Edited on 24-5-2007 by Organikum]

Sodium Cyanide Synth

jackson2004 - 23-6-2007 at 11:02

Has anyone tried the method involving iron oxide, soda ash and charcoal mixed together and fired to a red hot heat.
If so, how did it turn out?

Nicodem - 23-6-2007 at 23:19

Are you talking about some obscure method for producing steel?
This thread is about cyanides preparations (mostly by cyanate reduction) and if you check the formula for sodium cyanide it is NaCN, meaning that you need a source for the nitrogen (N) which is obviously lacking in your mixture (unless you impute N2 from air to chemically react there).

PS: It is customary in this forum to provide references for extraordinary claims (hence the word "science" in the forum's title).

Polverone - 24-6-2007 at 00:19

Quote:
Originally posted by Nicodem
Are you talking about some obscure method for producing steel?
This thread is about cyanides preparations (mostly by cyanate reduction) and if you check the formula for sodium cyanide it is NaCN, meaning that you need a source for the nitrogen (N) which is obviously lacking in your mixture (unless you impute N2 from air to chemically react there).

PS: It is customary in this forum to provide references for extraordinary claims (hence the word "science" in the forum's title).


I believe he's referring to the Bucher process for fixation of atmospheric nitrogen as cyanide. It seems to be (in)famous among non-professional chemists because it or a closely related process was recommended either by Kurt Saxon or Uncle Fester (can't recall which now) as an accessible method for cyanide production. Someone who was obviously cribbing from this source and had never attempted the process also did a first-person writeup that was enshrined on the inorganic section of rhodium.ws.

As an industrial process, its advantage was that it actually fixed nitrogen from the air rather than transforming already-fixed nitrogen. That is no great advantage for the home chemist, though. This process offers high-temperature obstacles like those of cyanate reduction, but no further advantages that I can see.

For a fairly comprehensive review of archaic cyanide processes, some fairly obscure yet perhaps suited to amateur use, see The Cyanide Industry Theoretically and Practically Considered. It was unfortunately published a decade before the Bucher process, but Google Books can provide further information on that particular process.

S.C. Wack - 24-6-2007 at 00:44

The method goes back to 1839. There is quite a bit of info on it in many old IEC articles. Thorpe has a long account by the chief chemist and later director of a company in Glasgow that used this process.

not_important - 24-6-2007 at 01:25

I know the Bucher process is mentioned in Textbook of Organic Chemistry by Joseph Scudder Chamberlain, which archive.org has. While the process goes way back, Bucher optimised it and made it commercially practical. When done on a large enough scale the overall process can be made exothermic, or you can capture the CO to make formate.

Nicodem - 24-6-2007 at 02:16

A relatively simple method of fixating N2 at 900-1000°C without the use of bacteria or other fancy chemistry? That is what I call some interesting inorganic chemistry. I was not aware of much N2 chemistry, besides certain metals like the alkali ones that burn in the atmosphere of N2 and certain industrial processes like hydrogenation of N2 or the cyanamide process. Searching for the nitrogen fixation and the Bucher Process I found this encyclopedic entry:
Quote:
Bucher Process.-The synthesis of sodium cyanide by the interaction of sodium carbonate, carbon and nitrogen in the presence of iron as a catalyst, according to the equation Na2C03+4C+N2 = 2NaCN+3CO 3 constitutes a promising method of nitrogen fixation, the commercial development of which is still in its infancy. The catalytic effect of iron in promoting this formation of cyanides. at relatively low temperatures (800-1,000° C.) was noted by Thompson in 1839. Bucher (Jour. Indust. and Eng. Chem., 1917, 9 . 2 33) drew renewed attention to the process, which has recently been developed industrially in the United States by the Nitrogen Products Co. According to the procedure adopted at Saltville,Virginia (Jour. Indust. and Eng. Chem., 1919, II. Imo), coke is ground to a fineness of 200 mesh, and after the admixture of a small quantity of iron the required quantity of soda ash is added. The charge is moistened slightly, kneaded, and extruded in the form of briquettes, which are dried by the action of flue gases. The briquettes are placed in vertical iron or nichrome retorts, which are heated externally in firebrick furnaces to a temperature of 900 to 1,000° C., a current of nitrogen being led through the retorts. The briquettes, after treatment, contain about 20% to 30% of cyanide, which, in the plant in question, is removed in a somewhat novel manner by subsequent extraction with liquid ammonia, in which sodium cyanide is readily soluble. During this extraction process, the main structure of the briquette remains undestroyed, and the uncombined residue may be used for further treatment with nitrogen. The chief technical difficulty lies in the rapid deterioration of the iron retorts at the temperature employed for fixation, the life of these being about 7 to 12 days. Nichrome retorts last longer, but are more expensive to replace. It has been proposed to use an electrically heated type of furnace in which the charge itself forms the resistance. Further, pure nitrogen, although conducive to a high yield of cyanide, is not essential for commercial success. Ferguson and Manning (Jour. Indust. and Eng. Chem., 1919, II. 94 6), in reviewing the replacement of nitrogen by producer gas containing carbon monoxide, state that at 1,000°C. the presence of 15% of carbon monoxide in the nitrogen reduces the yield of cyanide by about 30%, while, if the producer gas contains 60% of carbon monoxide, the yield is one-half of the value obtained with pure nitrogen. This inhibitive effect of carbon monoxide, the reason for which lies in the reversibility of the equation Na 2 CO 3 +4C+N 2 2NaCN+3CO, is even more pronounced at lower temperatures.

From: http://www.1911encyclopedia.org/Nitrogen_Fixation

OK, the process is too tedious as an amateur method of sodium cyanide production when compared to the discussed NaOCN reduction with carbon. Not only because of the need of oxygen free nitrogen, but also due to the messy workup. Still, I find it fascinating that Fe (or in situ formed Fe when Fe2O3 is used) can catalyze the reaction. How does it "capture" N2? Does iron form or equilibrates with Fe(II) nitride when heated in N2 atmosphere?

Given that not all have access to this paper I also pasted the excerpt regarding the industrial economics of the Bucher Process from:
Nitrogen: Its Fixation, Its Uses in Peace and War
Grinnell Jones
The Quarterly Journal of Economics, 34 (May, 1920), 391-431.
DOI:10.2307/1883359
Quote:

Cyanide Process

The only other process which merits discussion is the
Bucher process, which depends upon the fact that when
soda, carbon, and iron are intimately mixed and heated
to a red heat in the presence of nitrogen gas the nitrogen
is rapidly absorbed, resulting in the formation of sodium
cyanide mixed with the unchanged iron. The iron takes
no direct part in the reaction but the reaction will not
occur with any useful speed in the absence of iron. Altho
considerable difficulty has been encountered in the
operation of this process, it has been developed on a
commercial scale so recently that experience with it is
very brief but the best available information indicates
that the difficulties are not fundamental but can be surmounted
by changes in detail of design. The process
appears to be the most rational method known for the
manufacture of cyanides. Its development up to the
limits of the cyanide market may be predicted.
There is also a possibility that this process may produce
sodium cyanide at a cost low enough to make it a
suitable raw material for manufacture of many other
chemicals now made by quite different methods. If
sodium cyanide is steamed, it yields ammonia and sodium
formate. Sodium formate in turn will serve for the
manufacture of formic acid, for which a market of many
million pounds per year could easily be developed if its
price could be lowered substantially. Sodium formate
may also be readily converted into sodium oxalate and
this in turn into oxalic acid. Both the oxalic acid market
and the formic acid market of the world were dominated
by German manufacturers before the war; the new
process may destroy this German advantage. The output
of ammonia from the Bucher process may not, however,
necessarily be limited by the market for formic and
oxalic acids. By the action of air and steam at a low red
heat, sodium cyanide yields ammonia and soda. Since
the soda obtained may be used over and over again in
the process itself with consequent reduction in cost of
raw material, the development of the process, if financially
successful, is limited only by the demand for ammonia.
At present there is little prospect that ammonia
can be made as the principal product by this method,
but it may be produced as a by-product of the manufacture
of formic and oxalic acids.
Bucher even dreams of revolutionizing the process of
making steel, and obtaining sodium cyanide as a byproduct
of a new steel-making process. Pig iron, the
primary product of the iron and steel industry, contains
about 4 per cent of carbon. The process of making steel
consists essentially in reducing the carbon content to a
figure varying from about one-tenth of 1 per cent to 2
per cent, according to the variety of steel desired. In
the Bessemer converter, the carbon is burned out by
blowing a blast of air through the molten pig iron. Bucher
hopes to replace this air blast by a blast of nitrogen
carrying powdered soda and thereby to remove the
carbon as sodium cyanide. Sodium cyanide thus produced
would be so cheap that it might be converted by
treatment with steam into ammonia for fertilizer, and
soda for reuse in the steel-making operation. Since this
process has not yet passed the laboratory stage, prediction
of success would be rash. However, chemical science
has to its credit scores of triumphs inherently no
more difficult or improbable than this. There is at least
a hope that, within the next decade or two, the steel
industry may yield large amounts of nitrogen fertilizer
material as a by-product.

JohnWW - 24-6-2007 at 14:47

The only problem with that process, making NaCN from Na2CO3, C, and N2, heated together under pressure, as an intermediate to NH3 via steam hydrolysis, is that hydrolysis of NaCN produces, either as another intermediate or as a competing byproduct, HCN (prussic acid), which is a highly poisonous gas. Any escape of it would be a safety hazard.

S.C. Wack - 24-6-2007 at 20:51

The most relevant aforementioned IEC's

evil_lurker - 28-6-2007 at 11:00

Well I decided to attempt to whip up a bunch of cyanide this weekend.

I'm starting with the isopropyl nitrite synthesis as a reagent to manufacture oximinoacetone... basically I'm using the orgsyn reference above doubled in volume.

The reaction is going smoothly, with just a little bit more of a temperature rise than I would prefer (4ºC).

garage chemist - 28-6-2007 at 11:42

Wouldnt it be easier and less dangerous to melt potassium ferrocyanide with potash, directly giving KCN?

Anyway, its a new and interesting method. Keep us informed how it goes.

[Edited on 28-6-2007 by garage chemist]

JohnWW - 28-6-2007 at 13:28

That is, if Evil_Lurker lives to tell the tale. He had better wear a pretty good gas mask, and preferably diver-type breathing apparatus.

evil_lurker - 28-6-2007 at 14:09

Well the IPN synthesis went fairly well... there is a nice yellow non-polar layer on top of the spent NaNO2 solution just as orgsyn said there would be.



Total crude yield, 398g.

evil_lurker - 28-6-2007 at 14:23

Better pic of IPN in separatory funnel.

tito-o-mac - 6-7-2007 at 07:31

the poor man's James bon is crap... don't trust it.

Antwain - 28-7-2007 at 11:33

Hi all.

This is my first post of what will hopefully be many. I have always been fascinated by cyanide, even before I learned the reasons for its very strong binding to transition metals last year. Im hoping to make every metal cyanide complex possible (probably an unattainable goal, but my goal nonetheless).

Anyhow, recently I managed to distill some ferrocyanide + sulfuric acid into sodium hydroxide and I am going to clean this up ( the crappy hydroxide had carbonate in it I think, but it seems to still be insoluble in the resulting solution). Unfortunately it has been sitting in solution for some weeks, and I was wondering if anyone here knows about the hydrolysis to ammonium formate in aqueous solution. For instance, its winter and the solution will never have been over about 10*C - Does heating matter a great deal. And, I used a 5% excess of base (so that if a drop of sulfuric acid come over I wouldnt kill myself) does the pH affect the hydrolysis, and if so how.

Wiki has nothing on this, and google searches mostly reveal stuff about enzyme catalysis, and destruction of cyanide solutions - which is obviously not my goal :-). Any help would be appreciated. Essentially what I am wondering is whether or not much of my cyanide will have been destroyed. Incidently, I am going to dump my neaer saturated solution (~50mL) into 200mL of ethanol to precipitate it and hope for the best. Unfortunately acidified bleach will probably react with ethanol...? so how should I destroy that solution? In the meantime I will leave it in a bottle and see what you guys come up with.

12AX7 - 28-7-2007 at 14:12

A 5% excess of NaOH should get the pH in the 13 range, which should be good enough to keep HCN gas down. Don't know about hydrolysis, it can't be too bad...but maybe it can.

I would try to get it in crystalline form, being careful about heat and atmospheric CO2 and H2O decomposing it to HCN and NaOH. Once solid, it should be pretty stable, although it may still be prone to decomposition.

It would be a lot nicer if HCN were more acidic and had a much lower odor threshold than its lethal dose...

Tim

Antwain - 31-7-2007 at 08:19

Yeah, cyanide is the most poisonous thing I have ever attempted. But safety first - the minimum quoted minimum lethal dose corresponds to 160mg (for me) so I have some idea of how much that is in real terms. Not that I want to try taking 80mg.

Also, I forgot to post after my experiment... I was expecting a yield of ~70g theoretical. what I now have is a slurry in some ethanol which is ~25g and is probably only <5g of something (white powder), and 700mL of 80% ethanol solution with god only knows what in it. Sodium cyanide is quoted as being 'slightly soluble in ethanol' by merck and other sources, but is soluble in water 1:1@0*C, 2:1@100*C. Also sodium formate is 'almost insoluble in ethanol' and sodium hydroxide dissolves 1g in 7.2mL ethanol. Also given that the solution I had poured like conc. NaOH, ie. like honey, I wonder if maybe I never made much cyanide. A lot of gas bubbled through the solution (possibly because the base was too concentrated and it clogged) but I had a bleach soaked cotton ball in the release tube and a fan blowing into the shed.

Can anyone tell me if the concentration of the distillation mixture should be strong or weak? And does anyone know a good method for ensuring good contact between a gas/liquid interface. Also, I am thinking of using KOH (lab grade) next time, so if i dissolve this in ethanol so that the cyanide will precipitate out (1-3g per 100g ethanol solubility) is this going to help, or should I stick with aqueous solutions?

I have NO experience with practical gas chemistry so any help would be useful.

PS. I am currently thinking of using an upturned funnel, which is a pain because of the diameter of the beaker or whatever required + I can think of a bunch of ways in which this could fail and release HCN, or bubbling it through a long thin coloumn, of which I have none.

kmno4 - 1-8-2007 at 02:26

NaCN can be made in the same way as KCN, from K4[Fe....] and H2SO4/H3PO4. Diffrence is that NaCN crystallises as hydrate ( NaCNx0,5H2O or x1H2O) from EtOH so H2O must be quickly evaporated or hydrate should be kept at lower (<10 C) temperature. But it is much easier filter off NaCN than KCN, because of its much larger crystalls. It has also lower molar mass: 49g NaCN corresponds 65g KCN and there are less problems with stirring/filtering suspentions.
Generally, cyanides should not be kept/heated for a long time in strongly alkaline solutions - they decompose to brown products (propably polymeric CxNy ).
BTW.
Carl Scheele (discoverer of HCN and many others chemicals...) described smell and taste of HCN, ha ! It was hard man, almost dead because of Cl2... Great oldschool chemist :)


On the picture: about 60g NaCN (two runs). One run takes about 4-5 hours (from starting distilation to placing dry NaCN in a jar)
Everything can be done....;)

JohnWW - 1-8-2007 at 14:24

Quote:
Originally posted by kmno4(cut)
Generally, cyanides should not be kept/heated for a long time in strongly alkaline solutions - they decompose to brown products (propably polymeric CxNy ).

That would be (CN)x, polycyanogen, for which cyanides would firstly have to be hydrolysed to cyanogen, (CN)2. If a form of it exists as a long-chain linear molecule, amorphous and like a plastic, its formulation would be probably:
=N(+)=C(-)-N=C=N(+)=C(-)-N=C=N(+)=C(-)- etc.,
with the N atoms being alternately in the (V) and (III) oxidation states, and carbanion Cs bonded to quaternary ammonium Ns. This would be electrically conducting due to resonance delocalization of the electrons, resulting in the double and single bonds alternating in position, like graphite and polyacetylene and the electrically conducting plastics developed in recent years especially by Prof. Alan MacDiarmid (from New Zealand), and, similarly, likely to absorb all wavelengths of visible light. Two- and 3-dimensional polymeric structures may also be possible, but may not be electrically-conducting, or else may conduct electricity only in one direction.

With such an unsaturated structure, it is likely to react fairly readily with halogens and oxidants, and possibly sulfure, which has been reported.

I obtained 34 results for "polycyanogen" on Google, some of which are as follows.

This patent describes the electrochemical polymerization of cyanogen in solution, to give a polymer with a molecular weight over 500: http://www.freepatentsonline.com/4649038.html

According to http://doi.wiley.com/10.1002/pola.1993.080311020 (password-protected) and http://cat.inist.fr/?aModele=afficheN&cpsidt=8786062 it can be made by the reaction of KCN and ICN.

http://www.springerlink.com/index/P772VQ47H3552500.pdf and http://doi.wiley.com/10.1002/pola.1988.080260915 and http://linkinghub.elsevier.com/retrieve/pii/S004060900300304... and http://www.turpion.org/php/full/infoFT.phtml?journal_id=rc&a... (all password-protected) and http://www-g.eng.cam.ac.uk/edm/Publications/pdf/Rodil_TSF200... and http://202.127.1.11/surface%20science/517/51725.pdf describe its electrical conductivity and optical properties, as well as preparation.

This article (password-protected) describes a cross-linked 2-dimensional polymer: http://dx.doi.org/10.1002/chem.200501528

This article describes its possible use in photovoltaic cells, especially cross-linked with sulfur: http://www.phy-astr.gsu.edu/hastings/Publications/SYnthetic%...

If anyone has access to the password-restricted articles mentioned above, it would help if you can download them and piost them here, please. I am especially interested in the electrical conductivity angle and the possibility of photovoltaic cells.

kmno4 - 1-8-2007 at 15:24

You should have looked for "paracyanogen".
A lot of articles, for example:
J. CHEM. SOC. FARADAY TRANS., 1994, 90(2), 327-332
Structural Studies on Paracyanogen and Paraisocyanogen

Attachment: JCHEMSOC.pdf (221kB)
This file has been downloaded 1472 times

JohnWW - 1-8-2007 at 16:04

Thanks. I saw some mentions of paracyanogen in the search for "polycyanogen"; but the two appear to be two quite different polymeric substances. Paracyanogen consists of infinite chains, not of alternating C and N atoms as above, but of 6-membered rings (like tetracene, pentacene, etc.) consisting of alternating C and N atoms, and is a semiconductor due to resonance delocalization of electrons in alternating single and double C-N bonds, although probably not as conducting as polycyanogen.
BTW cyanogen has a much less stable isomer, isocyanogen, CN-CN, which similarly polymerizes to a solid compound, paraisocyanogen, which is a non-c0nductor

[Edited on 2-8-07 by JohnWW]

kmno4 - 1-8-2007 at 16:33

Searching on RSC site gives 0 (zero) articles with word "polycyanogen", ACS gives 2 articles. Compare to searching with "paracyanogen".
Searching "PbNO3" in Google also gives results..... :P

Formation of polycyanogen in the solid phase reaction of cyanogen iodide and potassium cyanide
Inorganica Chimica Acta, Volume 113, Issue 1, 3 March 1986, Pages 67-70
Z. Tóth, J. Gulyás and M. T. Beck ----> 'References' section

[Edited on 3-8-2007 by kmno4]

Antwain - 3-8-2007 at 17:37

kmo4, could you describe briefly the procedure you used, especially with regard to heating method (water bath, oil bath etc), endpoint, and workup (so you evaporated down an aqueous solution, and then precipitated it... is that right). Thanks heaps

I have seen references to polymers, specifically the tetramer of HCN, however the hydrolysis is described in multiple older books as being to ammonia + formate, or ammonium formate. I would put my money on this being a neutral/acid hydrolysis (ie HCN is a weak acid), although I cannot back this up with literature.

Antwain - 6-8-2007 at 15:17

And a word of warning (this was a pretty stupid mistake) :(

DON'T put alkaline solutions in PET bottles. Fortunately my shed floor is pavers so the solution mostly drained away, but I had to deal with several grams of what was probably sodium cyanide. And the plant next to that side of the shed died.

Elawr - 6-8-2007 at 18:16

It would probably be a good idea to keep some thiosulfate (hypo) on hand in case you inadvertently were to absorb enough CN- to make you sick. We keep it as the sodium salt to give IV for CN- poisoning. Works orally too. The thiosulfate ion in in vivo is a substrate for hepatic rhodanase enzymes which convert CN- to the much less toxic SCN- , which is excreted into the urine. Thiosulfate works prophylactically as well, animal studies have shown an increase in LD50 several-fold with thiosulfate on board. If one were to ingest some hypo prior to working with cyanides, then the urine could be easily checked qualitatively for SCN- by using Fe salts to form bright colored complexes. I do not know what the threshold is - whether or not it would pick up trace exposures too small to cause any symptoms.

At least cyanide is not cumulative. If it doesn't kill you outright you'll likely survive, although neurological trauma from cellular anoxia might be permanent!!!

[Edited on 6-8-2007 by Elawr]

12AX7 - 7-8-2007 at 13:26

Remember, the average healthy person has three times excess oxygen capacity in the blood (the excess is for athletic activity, of course). Sitting or laying doing very little doesn't consume much oxygen. So, you might figure the maximum dose is roughly the amount that inactivates 2/3 of the blood's active hemoglobin.

Tim

Antwain - 8-8-2007 at 00:50

actually, a much better antidote is amyl/butyl nitrite, which oxidises hemoglobin to met-hemoglobin (FeII to FeIII). Since we have that in plentiful supply it doesn't matter about the loss of the a bit of hemoglobin. This competes heavily with cytochrome a3, which we don't have much of, and is ESSENTIAL to the respiration process. Believe me, I had a test concerning this less than 2 months ago. The FeIII is much more susceptible to CN- than FeII due to the more polarising nature of the ion, and the charge carried by the cyanide. Sitting still and doing nothing will not help as much as you might think, although you probably shouldn't exercise just after you have been poisoned :)

Conversely, carbon monoxide, being a softer and uncharged base prefers the less polarising FeII, and will preferentially attack FeII in the body. Sitting still after carbon monoxide poisoning will help a great deal since only the 'carrying capacity' has been effected, whereas with cyanide the respiration process is effected, and once the cyanide has actually poisoned you (as opposed to merely been ingested or whatever) you are pretty well stuffed.

Thanks for the concern but I am being very careful, to the point of hindering my experiments, and for once in my life actually know what I am doing :>

btw, another old school method of dealing with poisoning involved egg white, but only for ingestion.

Antwain - 12-8-2007 at 01:53

Well I did it, kind of.

Theoretical reactions;
K4[Fe(CN)6] + 5H2SO4 ----> 4KHSO4 + FeSO4 + 6HCN
HCN + KOH ------> KCN + H2O

A distillation setup was put together consisting of a 1L RBF at the distilling end, a B24 water condenser (30cm) and a 500mL RBF for collection of the distillate. A short length of hose was placed on the end of the condenser tube, so that it sat around a centimeter above the magnetic stirrer in the receiving flask. K4[Fe(CN)6] (105.6g, 0.25mol) was placed in the 1L RBF and dissolved in water (200mL) with stirring and heat. KOH (84.2g, 1.51mol) was placed in the receiving flask and dissolved in water (200mL) with stirring. H2SO4 (100mL, 1.87mol, 49% excess) was mixed with water (200mL), and this was added to a dropping funnel on the distillation beaker, topping up as required.

After heating the ferrocyanide solution to reflux, the the sulfuric acid was added slowly of the course of ~1/2 hr. As soon as the acid started entering the flask bubbling occurred and the solution boiled. The solution began to change colour at the top to apple green. After the addition of all the acid, the entire solution had become apple green and the receiving flask had developed a slight yellow tint. It was also necessary to relieve the pressure several times to prevent the distillate from being sucked back up the condenser. The temperature of the vapor distilling over was not constant but stayed mostly at ~85*C for a while and then rose to 97*C.

Additional H2SO4 (20mL, 0.37mol) mixed with water (40mL) was added, and further boiling occurred, but the temperature of the vapor did not change nor did the appearance of the distillation solution. The flasks were cooled, and the green solution placed in a waste bottle. After rinsing the 1L flask and distillation setup, the placing of the flasks was reversed to as to distill out of the 500mL flask.

This solution was distilled until about 100mL remained, at which time the 500mL flask was disconnected while still quite warm. A VERY strong smell of ammonia was present. The solution was cooled in an ice bath, but simply gelled, so it was added to a larger beaker and ~350mL of ethanol added. This was filtered, which removed all but about 50mL of liquid. The gelatinous white powder was placed between two filter papers with many sheets of paper towel on either side, and a brick placed on top. After half an hour the filter parers, which were only damp, were placed on a warm heating mantle for around ~1/2hr. After this time the white powder was dry and was placed in a bottle (yield 33.3g, 0.51mol, 34%), however it had attacked the steel top of the heating mantle, leaving a ring of ferrocyanide on the filter paper.

So in conclusion, I got a pretty crappy yield, of probably not entirely the right stuff (it felt and smelt like sodium acetate does when heated, which is a worry because formate is one of the decomposition products) but there is definitely cyanide there as evidenced by it attacking my mantle. The ammoniacal smell stopped after the addition of alcohol so if I do this again (I have enough ferro for one more attempt) I will be making a solution of KOH in ethanol, and the KCN can precipitate out.

Also, does anyone know any good tests for cyanide. Ideally a volumetric quantitative one... I only have 0.1G accuracy and dont want to use all of my cyanide to get an assay. Perhaps a colourimetric one where I run something into a solution of 5.0g of white powder and eventually it changes colour. I can do volumes fairly well if they are not too small. It would be really good to know how much of my 'cyanide' is cyanide :)

[Edited on 12-8-2007 by Antwain]

thelittlestknife - 19-8-2007 at 12:32

This sounds a lot like the successful attempt above, but I had a few questions...

Ok. So I recently found an interesting recipe called the Bucher Process, which is probably old hat to a lot of the posters on this thread, but I was curious to test it out. Unfortunately the highest training I have in Chemistry is 11th grade(and even that wasn't too good), so I'll do my best to follow.

The Bucher Process (for those who don't know) is producing NaCN from Sodium Carbonate, Carbon and Nitrogen (just good ol' air) and Iron filings as a catalyst.
The Sodium Carbonate can be produced evidently by heating up Sodium Bicarbonate (Baking Soda) above 270 *C and I've found a chemistry website that I can obtain lab quality Graphite and Iron Filings. A yield of 5 grams of NaCN requires 5.41 grams of Sodium Carbonate (Na2CO3), 2.45 grams of Graphite (Carbon) and 4 grams of Iron Filings (Fe)

My questions regarding this process:
1. What materials will I need? I'm assuming a hot plate that can reach 270 *C and over. Perhaps a crucible for mixing the ingredients and placing on the hot plate for heating, or is there a better vessel? Tongues as not to get burned.
2. How will I know the Sodium Bicarbonate has successfully changed to Sodium Carbonate after heating? How long should I leave the baking soda over heat?
3. When heating the mixture, should I put all of the ingredients in together and then heat, or should I add ingredients intermittently in some precise order?
4. What temperature should I use for the mixture? Will I know when the process is complete?
5. Do I need to use something so separate the NaCN from the remaining Iron Filings?

Any help in this matter would be greatly appreciated.
Thanks!

Eclectic - 19-8-2007 at 13:53

Would you also like lessons in how to fly a plane but not land it?

thelittlestknife - 19-8-2007 at 15:19

Sure, anything to get me off the ground.

Antwain - 31-8-2007 at 11:23

I looked into the Bucher process before deciding how to try to make cyanide. After looking closely at it, I couldn't rationalise it actually working on a small scale, in an oxygen atmosphere, however there are ppl on the internet who claim it has worked. If you do decide to try it you will need a large excess of carbon, which will burn in the oxygen which comes free with every 4 parts of nitrogen in our air. Also, the equilibrium to form cyanide requires carbon monoxide to be removed from the vicinity... not easy when your excess carbon is going to be reacting with oxygen producing this. Finally, despites ppls claims, I think it would be much more likely to work with anhydrous potassium carbonate... at the temperatures required for the reaction, the sodium ferrocyanide (an intermediate) tends to want to break down to form nitrogen and carbon, while potassium ferrocyanide is stable to ~600*C

Filemon - 5-9-2007 at 15:03

Quote:
Originally posted by DDTea
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.


How the process it is? Do work if it chloroform and ammonia (ac)?

[Edited on 5-9-2007 by Filemon]

Filemon - 11-9-2007 at 14:36

Quote:
Originally posted by madscientist

[HCOO-][NH4+] --} HCONH2 + H2O
HCONH2 + H2O --} HCN + 2(H2O)



Where you have read that? I have never read that the formamide decompose HCN for heat. Have not you made a mistaked with the dehydration with P2O5?

S.C. Wack - 11-9-2007 at 15:26

There are numerous patents on this. It is not for amateurs.

Filemon - 22-9-2007 at 15:02

I have read that the reaction of an amide with NaBrO produces nitrile.

http://www.ugr.es/~quiored/qog/grup_fun/amidas.htm

With this reaction one could make with formamide NaCN. Does somebody know this reaction? For that one cannot make with NaClO?

amchem2000 - 22-9-2007 at 19:37

NH3(aq) + CHCl3 => HCN + 3HCl
- Aqueous Ammonia and chloroform are immiscible.
- At what temperature should they be heated to produce the reaction?

kmno4 - 23-9-2007 at 13:40

Quote:

NH3(aq) + CHCl3 => HCN + 3HCl

:D
It is not good equation.

amchem2000 - 23-9-2007 at 15:38

Quote:
Originally posted by kmno4
Quote:

NH3(aq) + CHCl3 => HCN + 3HCl

:D
It is not good equation.

Correction1 -
NH3(aq) + CHCl3 => HCN + 3HCl(aq)
OR
Correction2 -
NH4OH + CHCl3 => HCN + 3HCl + H2O

So again,
- To what temperature should this "mixture" be heated?
- For how long (Give any reference amounts)

DeAdFX - 23-9-2007 at 16:05

If I remember correctly doesn't the reaction between ammonia and chloroform produce methylamine or some sort of methylamine derivative?

S.C. Wack - 23-9-2007 at 18:13

Last time I checked ammonia forms salts with acids like HCl and HCN. Would you believe that if you could simply boil household ammonia and chloroform and get HCN, this would be mentioned somewhere?

Really hot. Residence time is probably not long.

Polverone - 23-9-2007 at 19:47

Household ammonia is too dilute. 30% technical/lab grade works ok with ethanol as cosolvent or maybe no cosolvent but using PTC; IIRC extra base (alkali hydroxide) is needed in either case. You can also prepare strong ammonia solution in place by reacting an ammonium salt with alkali hydroxide, but this of course leaves you with an even messier mixture of chemicals.

I never attempted to isolate pure cyanides by this method, but you can definitely get a strong positive on the prussian blue test. It uses relatively expensive materials and even in the best case the material thus prepared would contain more chloride than cyanide. It doesn't need extreme conditions, hard-to-obtain materials, or fancy apparatus, but it still never seemed attractive enough (compared with cyanate reduction) to try developing into a useful preparation.

amchem2000 - 23-9-2007 at 21:16

Quote:
Originally posted by Polverone
Household ammonia is too dilute. 30% technical/lab grade works ok with ethanol as cosolvent or maybe no cosolvent but using PTC; IIRC extra base (alkali hydroxide) is needed in either case. You can also prepare strong ammonia solution in place by reacting an ammonium salt with alkali hydroxide, but this of course leaves you with an even messier mixture of chemicals.

I never attempted to isolate pure cyanides by this method, but you can definitely get a strong positive on the prussian blue test. It uses relatively expensive materials and even in the best case the material thus prepared would contain more chloride than cyanide. It doesn't need extreme conditions, hard-to-obtain materials, or fancy apparatus, but it still never seemed attractive enough (compared with cyanate reduction) to try developing into a useful preparation.


=> Too dilute alright - so is the reaction slow or non-existent?
Since HCN evaporates at 26 oC and dilute HCL (in dilute ammonia solution) at much higher temperature, I assume that if we get the reaction started, then we can capture HCN (gas) in another bottle containing K/NaOH solution in alcohol - precipitating K/NaCN! This I think should give very pure K/NaCN (This knowledge is theoretical though).

=> The question is, at what temperature does the household ammonia solution and Chloroform start reacting (if they do at all) and how long does that take?
=> The problem would get complicated (a) if the reaction happens at temperature beyond CHCl3's BP (61.2 oC). Since at that point, Ammonia and Chloroform might just escape without reacting [what we capture in another bottle would then pretty much be everything from the previous bottle] (b) if the reaction is too slow (like several hours) as in that case Cyanide is sitting in a strong alkali alcohol solution which might then decompose (or polymerise).

Just a thought!

1) Where can we get strong ammonia solution
2) Forgive my ignorance - what is PTC?

I would really like to know someone has attempted this method successfully and if so the details of it.

BTW, just adding alkali to ammonia(dilute)+chloroform solution gives lot of heat [thats just alkali hydrolyzing] - but the end result had a layer of brown solution. Could this be the CN polymer that someone mentioned here?

12AX7 - 24-9-2007 at 01:39

Phase Transfer Catalyst.

Soap, in a very crude sense...

Tim

kmno4 - 24-9-2007 at 03:53

Quote:

Correction1 -
NH3(aq) + CHCl3 => HCN + 3HCl(aq)
OR
Correction2 -
NH4OH + CHCl3 => HCN + 3HCl + H2O

:D:D
These are not good equations - you do not know basics of chemistry.
It is the same as you would write:
NaOH +...+...+... => H2SO4 +...+...+.....
:P

amchem2000 - 24-9-2007 at 07:01

Quote:
Originally posted by kmno4
Quote:

Correction1 -
NH3(aq) + CHCl3 => HCN + 3HCl(aq)
OR
Correction2 -
NH4OH + CHCl3 => HCN + 3HCl + H2O

:D:D
These are not good equations - you do not know basics of chemistry.
It is the same as you would write:
NaOH +...+...+... => H2SO4 +...+...+.....
:P


They are not my equations. They were part of this thread since 2003. I am just asking if they work at all because of various other issues too.

In any case, I think they are 'good equations' but 'incomplete' and not really 'incorrect'. HCl could further react with ammonia giving ammonium chloride salt while part of HCN escapes out due to low BP. Many possibilies but we are looking at one section (equation) trying to see if that is significant enough to be considered here.

Some ppl on this forum claimed that it works. I just wanted to know what exactly did they do.
==========
BTW, kmno4, does prussian blue (ferric Ferro cyanide) react with dil H2SO4 directly upon heating? Or do we have to convert that to potassium ferro/i cyanide first. You seem to have used the pottasium varient - did you try using prussian blue directly?

Antwain - 24-9-2007 at 10:41

I cant see why it would matter at all to be honest, besides I have read literature that prussian blue is in fact ferric ferrocyanide AND ferrous ferricyanide (as I would have expected after one of my courses last year). So unless ferric ions interfere then you will have no problem - and i should point out that you end up with loosely packed ferrous sulfate floating around in all its pale green-ness after the distillation of ferrocyanide anyway.

Btw, the first time I tried to distill potassium ferrocyanide and sulfuric acid, but did not heat it adequately to drive off ALL the HCN the entire residue (coke) bottle became filled with deep blue, starting from the contact with air at the top of the bottle and gradually diffusing into the rest of the bottle. I still have to get around to destroying that at the end of the year... but since i just bought 10L of 'liquid pool chlorine' this shouldn't be difficult.

kmno4 - 24-9-2007 at 15:28

Quote:
Originally posted by amchem2000
BTW, kmno4, does prussian blue (ferric Ferro cyanide) react with dil H2SO4 directly upon heating? Or do we have to convert that to potassium ferro/i cyanide first. You seem to have used the pottasium varient - did you try using prussian blue directly?

I do not know if they react at all.
" You seem to have used the pottasium varient - did you try using prussian blue directly?"
I do not understant this question. I use H2SO4/K4[Fe(CN)6] as starting materials.... And as I wrote before:
2K4[Fe(CN)6]+3H2SO4 -> 6HCN + FeK2[Fe(CN)6]+3K2SO4
But FeK2[Fe(CN)6] is not so useless as it seemed to me. It can be converted, in a simple way, into K2Na2[Fe(CN)6] with aid of NaOH:
FeK2[Fe(CN)6]+2NaOH ->K2Na2[Fe(CN)6] + Fe(OH)2 (I have done it recently - messy job but it works :))
.... and reused again (as dry salt) for making HCN.
ps1
in Ullmann's enc. you can find b.p. of mixtures HCN-H2O and it can be seen that it is important to distill off everything from reaction mixture up to (almost) 100 C.
ps2
In "References" I gave old article about interaction between H2SO4 and K4[Fe(CN)6]
ps3
FeK2[Fe(CN)6] do not react (if even - veeeery slow) with ~40% H2SO4 (in boiling temp) - my own observation
BTW1
NaCN(aq) reacts easy with BzCl without cosolvent and heating but with addition of catalytic amount of TBACl and stirring ;)
BTW2
KCN reacts even with CH2Cl2 in acetone :o I am going to do this reaction with aquenous solution + TBACl
BTW3
This specific isonitrile reaction "NH3+NaOH+CHCl3" really gives NaCN in solution ( there is an article from ACS about it)

:)


[Edited on 25-9-2007 by kmno4]

amchem2000 - 29-9-2007 at 03:00

Quote:
Originally posted by Antwain

This solution was distilled until about 100mL remained, at which time the 500mL flask was disconnected while still quite warm. A VERY strong smell of ammonia was present. The solution was cooled in an ice bath, but simply gelled so it was added to a larger beaker and ~350mL of ethanol added. This was filtered, which removed all but about 50mL of liquid. The gelatinous white powder was placed between two filter papers with many sheets of paper towel on either side, and a brick placed on top. After half an hour the filter parers, which were only damp, were placed on a warm heating mantle for around ~1/2hr. After this time the white powder was dry and was placed in a bottle (yield 33.3g, 0.51mol, 34%), however it had attacked the steel top of the heating mantle, leaving a ring of ferrocyanide on the filter paper.

So in conclusion, I got a pretty crappy yield, of probably not entirely the right stuff (it felt and smelt like sodium acetate does when heated, which is a worry because formate is one of the decomposition products) but there is definitely cyanide there as evidenced by it attacking my mantle. The ammoniacal smell stopped after the addition of alcohol so if I do this again (I have enough ferro for one more attempt) I will be making a solution of KOH in ethanol, and the KCN can precipitate out.


[Edited on 12-8-2007 by Antwain]


How do you know that the 'jelly' substance is cyanide? It could just be mostly KOH (after drying) as the MSDS states that KCN/NaCN decomposes in water to KOH/NaOH + HCN.

Apparently anything short of looking at cyanide decomposes it to HCN - with water, air, CO2 etc.

NaCN (I think) does not precipitate but forms a jelly in the ethanol solution. How do u dry that jelly without decomposing NaCN? Using a hair dryer to dry it will probably decompose the substance.

amchem2000 - 29-9-2007 at 03:03

Quote:
Originally posted by kmno4
NaCN can be made in the same way as KCN, from K4[Fe....] and H2SO4/H3PO4. Diffrence is that NaCN crystallises as hydrate ( NaCNx0,5H2O or x1H2O) from EtOH so H2O must be quickly evaporated or hydrate should be kept at lower (<10 C) temperature. But it is much easier filter off NaCN than KCN, because of its much larger crystalls. It has also lower molar mass: 49g NaCN corresponds 65g KCN and there are less problems with stirring/filtering suspentions.
Generally, cyanides should not be kept/heated for a long time in strongly alkaline solutions - they decompose to brown products (propably polymeric CxNy ).
BTW.
Carl Scheele (discoverer of HCN and many others chemicals...) described smell and taste of HCN, ha ! It was hard man, almost dead because of Cl2... Great oldschool chemist :)


On the picture: about 60g NaCN (two runs). One run takes about 4-5 hours (from starting distilation to placing dry NaCN in a jar)
Everything can be done....;)


Same here. How do u know the content in the bottle isn't mostly NaOH? How will you evaporate the water from the 'jelly' substance (NaCN?) obtained in ethanol+NaOH solution?

kmno4 - 29-9-2007 at 04:27

Where have I written that it is 'jelly' ? My observations and easiness of filtering out NaCN hydrate say that it has crystalline form. Heating this hydrate up to ~80C causes its melting (looks like white thick honey, but not so tasty ;)) and (during stirring with spoon) as H2O goes away, it spills into white powder. At this moment it looks like (previously prepared) KCN. About KCN --> see page 4 of "Preparation of cyanides". Proof of content ? Read BTW1 in my last post (and yield of the precious nitrile was good ;)). Of course, some can say: it is bullshit, not NaCN in a jar but washing powder... But this powder works ;)

amchem2000 - 29-9-2007 at 09:02

- What is BzCl and TBACl (forgive my ignorance)?
- The reaction for HCN ad NaOH is thus (simplyfying to 1 equation),

HCN + NaOH <=> NaCN + H2O
with equilibrium biased towards the right side.
When heated dry (under burner, drier or open air), the HCN evaporates/boils faster than H2O. As a result, at the end of the drying process, you are left with mostly NaOH (and perhaps its sister products like Na2CO3 etc) and very little NaCN [Since NaCN decomposes very fast in the presence of H2O with 'drying']. The product might pass the prussian blue test but will be very low in NaCN - something like <5-10% (even that I doubt).

If you know that your yield is more than that, then it will be curious to know how you dried it.
Could you please explain your steps with amount of time spent on each step and the exact details?

Antwain - 29-9-2007 at 23:35

Quote:
Originally posted by amchem2000
How do you know that the 'jelly' substance is cyanide? It could just be mostly KOH (after drying) as the MSDS states that KCN/NaCN decomposes in water to KOH/NaOH + HCN.


Ummm.... rubbish?

Yes it is decomposed by CO2 + moisture
Yes other weak acids decompose it easily to HCN
Yes, it is strongly hydrolised in solution by the good old weak acid strong base (oversimplified) theory.
And yes, it polymerises and generally turns into things you do not want.


But, that is a load of crap. HCN will react very strongly towards the right hand side of this equilibrium, especially with an excess of base.
K/NaOH + HCN <------> K/NaCN + H2O

Also, I just properly read your last post. H2O, pKa~15; HCN, pKa~7

Once there is a good excess of a few % of hydroxide, there should be next to no HCN escaping. Since I designed the reaction with an excess of hydroxide I think loss of HCN was unlikely.

[Edited on 30-9-2007 by Antwain]

amchem2000 - 30-9-2007 at 20:06

Quote:
Originally posted by Antwain
:::
Also, I forgot to post after my experiment... I was expecting a yield of ~70g theoretical. what I now have is a slurry in some ethanol which is ~25g and is probably only <5g of something (white powder), and 700mL of 80% ethanol solution with god only knows what in it. Sodium cyanide is quoted as being 'slightly soluble in ethanol' by merck and other sources, but is soluble in water 1:1@0*C, 2:1@100*C. Also sodium formate is 'almost insoluble in ethanol' and sodium hydroxide dissolves 1g in 7.2mL ethanol. Also given that the solution I had poured like conc. NaOH, ie. like honey, I wonder if maybe I never made much cyanide. A lot of gas bubbled through the solution (possibly because the base was too concentrated and it clogged) but I had a bleach soaked cotton ball in the release tube and a fan blowing into the shed.

I have NO experience with practical gas chemistry so any help would be useful.

PS. I am currently thinking of using an upturned funnel, which is a pain because of the diameter of the beaker or whatever required + I can think of a bunch of ways in which this could fail and release HCN, or bubbling it through a long thin coloumn, of which I have none.


Antwain,
- Take about 15-20g of K-Ferricyanide
- Add lots of 30% H2SO4
- place in boiling water bath
- Put the tube from this into another bottle having denatured alcohol+NaOH. Place some part of the tube and the Alc+NaOH bottle in ice water.
- After about 1 hour bubbling, there will be virtually zero 'precipitate' (You would expect atleast few grams). The solution would turn a little green though.
- FerriCyanide+H2SO4 solution would turn into very deep blue to black color.
==========
- Clearly 'bubbling' doesn't do the trick.
- Any analysis on the colors obtained [green and deep blue/black]?
==========
Basically what did you do next.

Edit: Summarizing my understanding of Antwain's experiment. Description found to have lot of inconsistencies (pointed by kmno4 and Antwain).

[Edited on 2-10-2007 by amchem2000]

kmno4 - 1-10-2007 at 10:23

Quote:

Antwain,
- Took about 15-20g of K-Ferricyanide
(...)

Antwain took K4[Fe(CN)6] (ferro...) not K3[Fe(CN)6] (ferri...)
I think your ignorantion is too big to play with such things.
In Ullmann I have found also HCN/CN(-) equ. in diluted solutions. As you see, much less than 1% excess of (for example) NaOH is needed to prevent HCN formation. Smell of HCN is caused mainly by atmospheric CO2.
BTW.
TBACl is [N(n-Bu)4]Cl, one of the PTC catatysts. BzCN is øCH2CN.


[Edited on 1-10-2007 by kmno4]

amchem2000 - 1-10-2007 at 10:53

Quote:
Originally posted by kmno4
Quote:

Antwain,
- Took about 15-20g of K-Ferricyanide
(...)

Antwain took K4[Fe(CN)6] (ferro...) not K3[Fe(CN)6] (ferri...)
[Edited on 1-10-2007 by kmno4]


=> Doesn't this work for ferri?
=> What about other questions? Like if one should condense the 'HCN bubbles' to a liquid before introducing it to NaOH solution?

=========
I came across another equation which some people claimed to have worked -
K3[Fe(CN)6] + 3KOH = 6KCN + Fe(OH)3(ppt)

Did anyone try this route? It also looks safer (without involving HCN) and better.
However, mixing the two chemicals in water and heating may not do anything.
=========
Edit: Found the flaw in the equation - one book mentioned that Ferri gets converted to Ferro in the presense of alkali.

[Edited on 2-10-2007 by amchem2000]

12AX7 - 1-10-2007 at 12:56

What's the Kf of CN vs. OH? OH is pretty substantial, but so is CN.

Tim

Antwain - 1-10-2007 at 15:33

@amchem2000

Ok, first of all I con't remember if I posted my first attempt and don't have time to check, but a water bath is NOT HOT ENOUGH. I used a water bath the first time and so much cyanide was left in the distillation flask that it was not destroyed by adding several hundred mL of bleach, it is still deep blue. Use an oil bath (or sand of whatever, I prefer oil). Ferric ferricyanide is deep brown, god only knows what else you had in there.

Don't know if it works with ferricyanide, but making ferrocyanide is easy enough. *see post below

Also, I can't remember my exact reasoning, but I decided that ethanol+ NaOH was not acceptable. I think that NaCN is too soluble or NaOH not soluble enough.

The method you are referring to with KOH + ferrocyanide sounds like one I saw using K2CO3. I wont promise you this, but I really think the reverse reaction would happen, ie ferric hydroxide would dissolve in KCN. The method I saw requires fusion, and pouring off molten KCN. It doesn't sound much safer to me, and ferro/ferricyanide is libel to decompose to C and N at the temperatures required, I wouldn't expect a great yield.

[Edited on 2-10-2007 by Antwain]

kmno4 - 2-10-2007 at 02:26

Quote:
Originally posted by Antwain
(...)Filter off the zinc and crystalise the ZnSO4 + k4[Fe(CN)6]. Having ZnSO4 in there shouldn't matter.

Yeah.
And cows can fly....
ZnSO4 reacts with K4[Fe(CN)6].

[Edited on 2-10-2007 by kmno4]

Antwain - 2-10-2007 at 03:31

Your (accurate) sarcasm has been duly noted.

How about metabisulfite then? Easy to obtain from your local home brew section. Probably easier to get than zinc anyway. Serves me right for posting when I should be asleep :(

(incidentally, I expect that zinc ferrocyanide would work in place of potassium ferrocyanide)

Pixicious - 28-1-2008 at 16:44

How would you suggest building an oxygen-free crucible?

Pixicious - 5-2-2008 at 08:14

Sorry for the second post. This one is for Meyer.

I'm not a chemist but it appears in the second process (although it is weird this doesn't appear on wikipedia since it appears to be a 1839 process but only in its infancy in commerical production now) that you need a temperature of 900-1000C, which I believe is a greater temperature than that of glass.

The formulas are fine but I couldn't tell you anything more. This is just a passing interest for me.

EDIT:
Quote:

OK, the process is too tedious as an amateur method of sodium cyanide production when compared to the discussed NaOCN reduction with carbon. Not only because of the need of oxygen free nitrogen, but also due to the messy workup. Still, I find it fascinating that Fe (or in situ formed Fe when Fe2O3 is used) can catalyze the reaction. How does it "capture" N2? Does iron form or equilibrates with Fe(II) nitride when heated in N2 atmosphere?


Couldn't it be possible to fill a cruitable (upside down ofc) with Nitrogen which is obtained by a reaction of Ammonia Chloride and Sodium Hydroxide in a mixture of water which is sent through an iron catalyst to seperate the Hydrogen and Nitrogen. The mixture required is placed on top of a lid and the lid is very carefully and securely attached to the upside down cruitable. The cruitable can then be shaken, dropped and carelessly handled without air or more importantly oxygen added to the mixture. Then this is put in side a furnance at temperatures of 950-1000*C. Afterward the container has cooled it is opened and a yeld of 30-40% NaCN is removed.

DO NOT TRY THIS AT HOME. I AM NOT AN EXPERIENCED CHEMIST. THIS COULD EXPLODE.

[Edited on 6-2-2008 by Pixicious]

Cyanogen Cyanide chemistry

franklyn - 16-2-2008 at 11:22

The Chemistry of Cyanogen Compounds and Their Manufacture and Estimation
Herbert E. Williams - 1915
http://books.google.com/books/pdf/The_Chemistry_of_Cyanogen_...
Also covers fulminate compounds
Page 177 gives this reference for Cyanuric chloride, needs phosphorus pentachloride though.
Beilstein, A., 116, 357

.

Pixicious - 21-2-2008 at 04:51

Quote:

- Any analysis on the colors obtained [green and deep blue/black]?


I've read it could be a reaction between iron and the other substances.

K4[Fe(CN)6] + H2SO4 -> FeSO4 + 2HCN + 4KCN


Iron Sulphate is one possibility. After checking Wiki it could be the reason for the green colour.

Can someone say the formula above may be correct? What may be the other colours in his "mixture" I know HCN is formed when ferrocyanide and sulphuric acid are mixed. KCN was just the letters which were left. Iron Sulphuate was used because it seemed to fit the equation and was green in colour.

Sorry I couldn't have been more help.

grind - 23-2-2008 at 15:00

There is another way to make KCN. I´ve tried this:
Make a concentrated solution of KOH in absolute ethanol. Cool this with ice/NaCl. Now slowly drop in a solution of acetone cyanohydrine in ethanol. KCN is precipitated. Filter, wash with little ethanol, dry in vacuum at first at RT, later at 80°C. This yields 50% of very pure KCN.

(CH3)2C(OH)CN + KOH ---> KCN + CH3COCH3 + H2O

The only problem would be the accessibility of the cyanohydrine, but this method works fine.

[Edited on 23-2-2008 by grind]

Pixicious - 24-2-2008 at 01:17

It would be interesting to know how to make cyanohydrin.

If so that is a really interesting method because potash would be really easy for people to come by here.

Pixicious - 24-2-2008 at 01:20

13 is unlucky, 14 is nice.

I'm not sure if you mean ethanol or methanol with the formula you mentioned.

Nicodem - 24-2-2008 at 01:35

Quote:
Originally posted by Pixicious
It would be interesting to know how to make cyanohydrin.

Acetone cyanohydrin is made by the reversed reaction (the reaction is catalysed by traces of KCN or any other base):
HCN + CH<sub>3</sub>COCH<sub>3</sub> ---> (CH<sub>3</sub>;)<sub>2</sub>C(OH)CN
I'm quite sure you can find the exact experimental in Vogel's, Organikum or any other book on laboratory practice.

PS: Try not to double post. Use the edit function instead.

grind - 24-2-2008 at 07:11

The way via the cyanohydrine only makes sense, when you can buy the cyanohydrine. It´s cheap but very toxic and I think for most people hard to get.

Pixicious - 27-2-2008 at 02:41

Quote:

1) Where can we get strong ammonia solution


You mix NH4Cl (Ammonium Chloride) in water, this is not exothermic and then add NaOH (Sodium Hydroxide), this is exothermic.

If in the right quantites you will produce salt so there is no need to worry when you wash the solution away. The gas given off is NH3, feed this through water and you have a very concentrated NH4 solution.

NH4Cl + NaOH + H2O -> NH3 + 2H20 + NaCl

quicksilver - 27-2-2008 at 11:41

Quote:
Originally posted by amchem2000
1) Where can we get strong ammonia solution

For absolute lowest cost I like ammonium sulfate (available at any garden supply, hardware store and sodium hydroxide (lye) via the above mechanism of gas generation through water. In terms of cost for either anhydrous ammonia gas or ammonia solution, you are actually dealing with pennies.

497 - 7-4-2008 at 17:28

I have a solution of an unknown amount of sodium cyanide with quite a bit of sodium carbonate and probably some sodium cyanate along with. I had the idea to add calcium hydroxide forming calcium carbonate precipitate. This should also produce calcium cyanide right? Then I read that calcium cyanide is unstable in water, so would I just get a bunch of HCN or what? There must be a better way to separate them.

Pixicious - 8-4-2008 at 23:45

497: I don't know.

I just came here because from things I have been reading there is another way of producing NaCN from just household.

This method relies on Ammonia, Chloroform and Sodium Hydroxide producing Sodium Cyanide.

A couple of questions arrise. How are the three mixed together? NaOH + NH3(aq) cannot be in the same solution together, NaOH + CHCl3 -> NaCl + H2O + CCl3 and, NH3(aq) + CHCl3 is the only method I can think of mixing the two before dripping in the Sodium Hydroxide. Although I have a memory which says this produces HCN.

Is the reaction of Chloroform and Ammonia exothermic? If so is HCN, HCl or both released as a gas, or do either or both remain a liquid? I think this is an essential question for anybody here. Especially for purification.

The method involves just Ammonia, which is obtained by concentrating Ammonia solutions through heat into a much smaller amount of water. Calcium Carbonate which is used to produce Calcium Hydroxide, Sodium Hydroxide and Acetone. Also needed is Acetic Acid and Sodium Hypochlorite.

Obviously you will need to distill and dry at several points, and I am not sure where you can produce drying stuff from household. (Maximum temperture needed is: 850oC and that is only to produce Sodium Hydroxide.)

I would like to know if there is a known method of reacting Sodium Hypochlorite to form Calcium Hypochlorite power.

The seperation as described of HCl and HCN and an excess of NH3. (Just so all the chloroform has reacted) is to bring it to a boil of 26.5oC and bring a controlled release of HCN gas insealed containers feeding into a NaOH and methanol solution? Or in this case would the Hydrochloric acid not bound with the Hydrogen Cyanide and will be released as gas just leaving pure Hydrogen Cyanide..

[Edited on 9-4-2008 by Pixicious]

Pixicious - 10-4-2008 at 01:02

If you bubble Ammonia through a solution of Hydrogen Cyanide and Hydrochloric Acid, would the Hydrochloric Acid (assuming it remains a solution in HCN) react to form Ammonium Chloride?

Then would it just be a simple case to filter the Ammonium Chloride from Hydrogen Cyanide to obtain a pure form of Hydrogen Cyanide.

Something I've been wanting to pick with you for a long time Polverone. If to achieve HCN all you have to do is slightly warm acidified Potassium Ferrocyanide, why is it not considered poisonious to ingest?

[Edited on 10-4-2008 by Pixicious]

Sauron - 10-4-2008 at 05:08

Acetone cyanohydrin is easy. Yes the prep is in Vogel; he cadged it from Org.Syn as usual. See it there for more details and a larger scale.

I tried to order some from Aldrich and they wanted something like $2000 for ocean freight hazmat. So I got it from Merck. No hazmat which is entirely America shooting itself in the foot.

I use it in one of the processes to prepare AIBN, the radical initiator for polymerizations and some chlorinations. Could have made my own but that would have meant making anhydrous HCN and better to work around that, than to work around it, if you get my meaning.

497 - 8-5-2008 at 22:31

I have heard mention of fusing calcium cyanamide with Na/KCO3 to yield the respective cyanide along with CaO and oxygen. If you can get/make CaCN2 easily this might be useful. Sorry I don't have more details, I'm way too busy with school to work on this.

And sorry if this is old news, its been a while since I read this thread in detail.

[Edited on 8-5-2008 by 497]

NaCN via Nitrite + Acetate

Axt - 6-6-2008 at 20:31

CH3COONa + NaNO2 --> [ONCH2COONa] --> NaCN + NaHCO3 + H2O

See the attachment, in german so I cant make a lot of it out, would be good if someone can confirm what I've written here.

By heating a mixture of 12g sodium acetate with 10g sodium nitrite with added bicarbonate (to stop or at least control the deflagration of the mixture) it gives NaCN in 25% yield. This isn't a lot, ~1.8g per 10g of nitrite. Gasseous HCN and H2O are released during the reaction.

K nitrate + K acetate also forms some cyanide, presumably through the nitrite intermediate.

Is the extraction of ther NaCN mentioned in the article? How was it analysed to determine 25%? It says something about 70% alcohol but I cant make it out.

Maybe its possible to increase the yield by trapping the lost HCN via NaOH/EtOH, though I suspect this will also have a bicarbonate impurity.

Attachment: nitrite-cyanide ocr.pdf (97kB)
This file has been downloaded 1301 times

Formatik - 6-6-2008 at 23:28

In this process without the soda they had a violent explosion from it (I'm not sure what the source of explosion is, if it is the possible reaction as an oxidizer mixture or HCN as according to Urbanski hydrogen cyanide is explosive, and alkalinity can polymerize it explosively). The procedure they give they say it occurs without explosion. The proportion of soda needs to be as described, already 3g of mixture and 2 g soda ratio deflagrates pretty vigorously. Though a 1:1 mass ratio in a metal bath starts to soften and inflate around 300 deg., at 375 deg. water and significant amounts of HCN is let free under fizzling and freezes to a porous mixture of carbonic acid salt and NaCN.

12 g sodium acetate and 10 g NaNO2 with 22 g soda (Na2CO3) in a porcellain crucible is heated over a free flame. This will soften and glow, as soon as the reaction temperature is reached, there is a lively glimmering, but it occurs without explosion or spattering, whereas water and noticeable amounts of hydrogen cyanide escape. The porous, crumbling mass is colored dark from the separated coal. By boiling with 70% pure alcohol the NaCN can be extracted and then after a repeated recrystallization by cooling an aqueous-alcoholic solution, can the plates as described by Joannis be obtained.

They did the determination of yield by precipitating AgCN from the NaCN, and then weighed it. The yield of NaCN is dependent on the type of heating, and from that no more than 25% yield results.

Note: NaHCO3 will lose mass (37% mass) as it is heated at low to moderate temperatures forming H2O and CO2. Na2CO3 forms several hydrates and will also lose mass. Both of these might skew the ratio unfavorably. Also reading further the explosion source is likley a redox reaction maybe going through unstable intermediates, as NaNO2 reacts similarily with sodium formate, propionate, or tartrate, also forming more or less NaCN.

[Edited on 7-6-2008 by Schockwave]

Ephoton - 8-6-2008 at 22:58

an idea :)

if one was to go from sodium or potassium cyanate then
any reducing agent that works in the conversion of nitrates
too nitrites should work.

there was a post in this forum some were from a gentleman
from the upper block of europe stating it was impossible to
get nitrites in his area. he stated that the general way to
obtain these was to heat the nitrate untill it was molten then
add lead tartrate.

after a bit of thought and some looking around and a few small
tests this would seem to me to be the best way to make
very pure cyanide as well.

I would expect any problems found in the conversion of one
would also be seen in the conversion of the other (ie nitrate
or cyanate)

by the way thanx KMnO4 for the hint it was a true killer :)
just as I thought to be honest it will stay at the amide.

and thanx Nicodem for posting the entire article.



[Edited on 9-6-2008 by Ephoton]

Axt - 13-6-2008 at 11:12

Thanks for the translation Schockwave, this may be the explanation for its explosive nature.

The double salt, KCN.KNO2.H2O, is obtained by dissolving potassium nitrite (50 grams) aiid potassium cyanide (20 grams) in the smallest possible quantity of water and allowing the solution to evaporate over sulphuric acid. Potassium cyanide separates first, and then the new double salt in short, characteristic prisms. It explodes with a loud report when heated at 400-500°. J. Chem. Soc., Abstr. 70, I, 69 1896.

[Edited on 14-6-2008 by Axt]

Cyanide manufacture

jarynth - 9-10-2008 at 16:10

Gary R. Maxwell's Synthetic Nitrogen Products (Kluwer) offers a quick survey of the industrial syntheses of basic nitrogen compounds. Chapter 19 is dedicated to hydrogen cyanide.

I won't even mention the high pressure gas phase processes, but the following could be useful in an amateur setting, provided the necessary precaution is met.

1) 'The dehydration of formamide is conducted in iron catalyst at 380°C to 430°C under reduced pressure. The tubes are filed with Fe or Al phosphate catalyst that also contains Mg, Ca, Zn or Mn as promoters. The selectivity to HCN is 92% to 95%'
(Weissermehl, Arpe Industrial organic chemistry VCH 1997)

2) It's a common oppinion that this organic compound cannot be turned appreciably into ionic cyanides; luckily this is true as far as the human metabolism goes, but the Japanese patent 10167721 makes a refreshing claim. For those who can find acetonitrile cheaply, and with a tube furnace, consider this:
'PROBLEM TO BE SOLVED: To efficiently convert acetonitrile into prussic acid by a simple method by using activated carbon as a catalyst in producing prussic acid by reacting acetonitrile with oxygen or oxygen and ammonia. SOLUTION: In this method for producing prussic acid by effectively utilizing acetonitrile as a by-product in production of acrylonitrile, activated carbon is used as a catalyst. Industrially useful activated carbon is generally used. The shape of activated carbon may be granule of powder. Pure acetonitrile is not necessarily required and a mixture may be used. Oxygen may be diluted with an inert gas such as nitrogen or may be supplied as air. The amount of oxygen used is preferably 2-3 mols based on 1mol of acetonitrile. The reaction temperature is preferably 400-500 deg.C. The reaction pressure is preferably high with respect to contact efficiency with the catalyst and may be normal pressure or slightly under pressure in terms of simplicity of facilities. The reaction time is preferably about 0.5-5 seconds.'

len2 - 22-2-2009 at 04:51

Someone on the forum was interested in this so I tried it out.
Quote:


Decomposition of Potassium Ferricyanide by the Action of Heat. V. CUTTICA (Guzsetta, 1922, 52, i, 20-.25).-

Protracted heating of potassium ferricyanide at 230C results in complete decomposition of the salt according to the equation

2K3Fe(CN)6 = 2FeC2 + 2N2 + CN2 + 6KCN.

658 56 52 390

The intermediate green substance formed during the heating (cf. Locke and Edwards, A., 1899, i, 407, 557; Cuttica and Canneri, A., 1921, i, 322) exhibits the oxidising properties of the original salt, but differs from it in certain of its reactions, and contains complex iron cyanides with less than six cyanogen groups in the molecule.



Ferricyanide is superior to the ferro salt in that there is no water of crystalization (.3H2O for ferro) to speak off. But at 230C there was almost no weight loss as per formula - and there was only 0.1gms lost at 480C for up to two hours heating. This puts in doubt the report above if it refers to anything like reasonable reaction time, as chemical reaction rates on average double every 10C or so. Nonetheless some iron was reduced as addition of HCl resulted in deep blue colouration indicating some Fe(II) present (the original ferricyanide gives a deep yellow colouration only).

4.4gms ferricyanide was then held at 180C for 1hr in a box oven to rid of any moisture, then heat was raised to 400C for 0.5hrs, 640C 2hrs, 680C 0.5hr. A borosilicate tube blocked with glass wool was used as container - which was not ideal as it softened and bent, while KCN being basic attacks the glass. Nonetheless at the end the bent tube was filled with a white powder and black granules, was brocken, ground up, and 50ml H2O added and mixed. Filtration under vacuum gave a clear solution (no ferri evident in product). This shouldnt be evaporated as KCN decomposes in boiling water. Alcohol added (100ml) immediately gave a white precipitate which was filtered and dried. 1gm obtained, which = 40% yield - would be higher for larger batches.

To test for KCNO 0.1gms was dissolved in H2O/alcohol and HCl (conc) added. A heavy mist of HCN resulted, but there was no effervescense (CO2) - this quick test indicates no substantial oxidation of KCN had occurred.

[Edited on 22-2-2009 by len2]

densest - 23-2-2009 at 07:44

One approach which I saw appeared to work:

To a cold saturated solution of KOH was added K4Fe(CN)6 crystals until no more would dissolve. The flask was sealed with plastic film to exclude CO2 and O2. Over a period of some days, Fe hydroxides and oxides precipitated, and the color of the solution changed from yellow-green to clear. The supernatant was decanted. On further chilling, transparent square plates and small cubes crystallized. Filtered quickly, washed with a minimum of very cold distilled water, a very small amount (milligrams) gave a very strong blue reaction with FeSO4 solution.

I believe it took several weeks overall, using an outdoor shed during autumn. It would seem to depend on KCN being somewhat less soluble than KOH or K2CO3 and very little O2 being available to destroy the KCN. Perhaps the air in the flask could be displaced with something else to improve the yield.

According to an old Chem Rubber handbook, the only likely substance in that solution which crystallizes to a square or cubic form would be KCN giving a second reason to believe the process worked.

S.C. Wack - 23-2-2009 at 18:35

I'm sure people will be giving that a try now.

----

There are many places where one can find a mini-review of cyanide, and many resources have been posted on this board over the years. At the very beginning, Beilstein mentions a review in JACS
http://books.google.com/books?id=lAkSAAAAIAAJ&pg=PA31
there is also
http://books.google.com/books?id=lAkSAAAAIAAJ&pg=PA3
These are not the greatest, but they are informative to those not aware of the history (to 1889) and it gives me something to post.

If anyone is interested in looking up old things probably in a different language, since I have these old photocopies and they're just gathering dust and personally I like it when people post things such as Beilstein, 14 pages from the Hauptwerk on preparation/formation/occurrence of HCN, the complete entries for NH4CN, NaCN, K4Fe(CN)6, K3Fe(CN)6, and most of KCN.

Attachment: beilstein_cn.pdf (1.7MB)
This file has been downloaded 2011 times

len1 - 23-2-2009 at 19:27

Thanks for the info SC Wack. But none of the links work. The first two only give me the title pages the last hangs the computer.

ANYONE WHO WORKS WITH CYANIDES INCLUDING MYSELF MUST WEAR A GAS MASK, GLOVES and GLASSES!. Even in this case when theoretically no HCN is generated KCN spilled on a stray drop of HCl, can generate enough HCN to kill, especially if you are like myself and cant smell it. Grinding or picking KCN can stray particles into your face and mouth - also enough to kill. A mask will guard against all of this. Gloves give protection against KCN dissolving in skin moisture and penetrating though cuts etc. Glasses protect against KCN particles flicked into the eye dissolving in tears, being absorbed, and killing. Symptoms of mild CN poisoning resemble symptoms of fear of having been poisoned (anxiety).

Ive done the Ksp calculations, and the KOH method must work and it must work even better with K3FeCN6 since its last cyanide is weakly bound (making it poisnous) so that it can be substantially separated even in boiling water

[Fe(CN)6]3- + OH- -> [Fe(CN)5OH]3- + CN-; [Fe(CN)6]3- + H2O -> [Fe(CN)5H2O]2- + CN-


Removal of all the cyanides if you check the K's proceeds because of the low Ksp of iron hydroxide. BUT its all very slow and inefficient. In practice my method is better: simplest method imaginable - no mixing, weighing etc; takes a few hrs; directly gives pure KCN; is safe for non-specialist labs - no HCN at any stage

Yiled can be improved, but at the expense of a lot more dangerous work. At this level I think this method is perfect.

[Edited on 24-2-2009 by len1]

S.C. Wack - 24-2-2009 at 03:59

Quote:
Originally posted by len1
Thanks for the info SC Wack. But none of the links work. The first two only give me the title pages the last hangs the computer


As I told Sauron to some argumentation last week, the Google links work perfectly for those in certain countries, like the USA, however Polverone deleted my explanation on how others can get around this so I ought not post it again. Nor is there anything wrong with the pdf, I'm always the first one to download to make sure it works and it just worked again. All attachment downloads in the past few months stop at say 98% for 10 seconds then finish. Maybe its a virus scanning thing or something, or just a problem, in any case that's the way it is and they always finish for me.

[Edited on 24-2-2009 by S.C. Wack]

not_important - 24-2-2009 at 05:05

For me the attached PDF stalled closer to 20 seconds, but did finish and yield a readable file.

The Google links work when accessed through a proxy in the U.S. It is amusing to read
Quote:
In 1837 Neilson first introduced the use of the hot blast at the Clyde iron furnaces. Shortly afterwards,1 a peculiar exudation of fused salt which hardened on reaching the air to a white, opaque mass was noticed upon the walls of the furnace near the boshes. The substance was regarded with much curiosity and it is related by Clark, who made the first analysis of the product, that its alkaline character was soon discovered by the workman and that it was used by the wife of one of them, for a time, as a substitute for soap in washing clothes.2

Clark's analysis allowed it to contain potassium cyanide 43.4%, potassium carbonate 45.8%. No ferrocyanide was present.

len1 - 24-2-2009 at 15:46

Quote:
Originally posted by not_important
it was used by the wife of one of them, for a time, as a substitute for soap in washing clothes.2


I guess it was a very short time ...

A useful thing I found when working with cyanides is to have a developing solution - a few specks of FeCl3 (PCB etchant) and a few specs of FeSO4 (garden fertilizer) dissolved in 10ml H2O, dab it around the lab to locate specs of KCN which might have been left lying around. Even traces of KCN give an intense blue colouration (as of course would ferro/ferri cyanides)

Magpie - 25-2-2009 at 10:38

len1, there is the Liebig method for the determination of cyanide. This may be of help in your optimization. I've extracted this from "Quantitative Analysis," 3rd Ed, 1951, p.305, by Pierce & Haenisch, as follows:

"Procedure. To the dissolved sample (note 1) which should contain 6-8 mmol of cyanide ion, add 30-40 mmol of ammonium hydroxide and 0.1-0.2 g potassium iodide, and dilute to a volume of 100 ml. Titrate with standard 0.1M silver nitrate until the addition of 1 drop of reagent causes the appearance of a permanent turbidity in the solution (note 2).

Notes. 1. Keep constantly in mind the very poisonous nature of potassium cyanide. Be sure to wash out the solution with a large quantity of water at the conclusion of the determination. Do not allow any waste cyanide to stand in a sink where it may come in contact with acids and evolve hydrogen cyanide gas."

The reaction up to the endpoint is:

Ag+ + 2CN- ----> [Ag(CN)2]-

So, for every mole of Ag+ consumed there was 2 moles of cyanide present.

len2 - 25-2-2009 at 15:06

Thanks Magpie.

One thing i was trying to avoid is using silver - why is it so popular in titrations of CN? Its $55/10gms. So for 8mmol a sinle titration is $2.40! The other thing is AgCNO is also insoluble. Is there any statement to the effect of cyanates? I suppose i could make some cyanate and see.

[Edited on 26-2-2009 by len2]
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