Preparation of cyanides

Quote: Originally posted by lysander

For my fourth attempt I tried the Brauer/Vizine formula, which essentially doubles the amount of ferrocyanide but still uses a 25% dilution of H2SO4. Combine 100mL distilled water with 100mL H2SO4. This reaction heats the dilute to 100C. Therefore wait for it to cool back to room temperature Add 211g K4FE(CN)6 trihydrate to 1 liter boiling flask. Add 200mL water and begin stirring. (This requires a more powerful stirrer). Add the cooled 200mL H2SO4 dilute to boiling flask. Heat solution to 60C. Run for <i>four hours</i>. <B><I>Nothing</B></I> evolved! Raised heat to 80C. Managed to get 15mL of condensate in cooled collection flask that smells of HCN, but also of something more strong and pungent. Hang head in disappointment. Here's a photo of the apparatus running after about an hour: The color gets perhaps a <i>little</i> darker by the end, as seen in this video taken right before shutdown: http://youtu.be/dTFK_o-D_JI (Compare that color to the two runs where I dropped the concentrated H2SO4 into the ferricyanide solution: http://youtu.be/SqLJU862yMQ Questions: A. Does the color indicate any failure? What is the expected progression of color over the course of the reaction? B. Is HCN miscible with H2SO4? (If not that would explain the two layers I'm getting in what little I collect.) [Edited on 15-9-2015 by lysander]

Quote: Originally posted by Dan Vizine

I have never observed that color at any stage. When the ferricyanide was added to stirred, hot 25% sulfuric acid (or the reverse, it makes no difference) the suspension turns deep blue very quickly.

This might be a key to solving my ongoing failure. For attempt #5 tonight I put all liquid in the boiling flask first, and then began to add the ferrocyanide with the mixer going. (I can always see the mixer working because I can see the vortex.) It was turning blue as it was being added, until I increased the rate of addition at which point it became briefly milky before starting to turn light green.

Of course yellow + blue = green, but it's not just a failure of the yellow ferrocyanide to react. Something else is going on, because after removing the addition funnel I wafted the opening towards my nose: again, overwhelming the hint of HCN was something far more pungent -- the same nauseating thing that overwhelmed the HCN odor in the past condensed fractions that have two immiscible layers. I can't put my finger on it, but I think it is also present in the smoke of burning garbage containing plastics.

Suffice it to say that I think the mixing of the reagents has to be done in a more controlled fashion than documented anywhere yet. Although, embarrassingly, that's not quite true: Ledgard's instructions, of all things, noted that the H2SO4 dilute should be added dropwise to the mixing solution of the ferrocyanide.

Maybe sixth time's the charm?

[Edited on 20-9-2015 by lysander]

Quote: Originally posted by Dan Vizine

You're using the ferrocyanide? Stupid me, I thought you were using the ferricyanide (orange-red). While both will give HCN ultimately, you can't just assume a procedure specific to the ferricyanide will be correct for the ferrocyanide.

Well if there's an award for worst experimental chemist I'd like to nominate myself. I've tried every formulation I can find documented of reacting K-ferrocyanide with H2SO4 to produce HCN. I even carefully followed Williams to include a CuCl catalyst dissolved in HCl. No matter what I do I can't get more than about 10mL of HCN from 200g of K-ferrocyanide or -ferricyanide. Running longer or hotter just gets more water.

"Well fine," I thought. "I'll go back to the old-school method of boiling it off of cyan-salts with H2SO4." So I smelted up a nice batch of K-ferrocyanide with Na2CO3, then dripped H2SO4 into the results. Turns out there's more that reacts with H2SO4 in the byproducts (carbon and iron compounds) than just the cyan-salts. Also turns out a Liebig condenser isn't adequate to condense whatever it is that boils off.

Also turns out that it leaves some black residue in the reaction flask that neither acids nor bases nor detergents will remove. Any ideas on other compounds that might clean this?

Lysander, use bleach. It's highly effective.

As I've been waiting for the winter to end so that I can finally complete the thorium production run (since it's going to be done outside, no question about it), I thought I'd do a relatively safe reaction during the cold winter months.

There have been an incredible number of verbal descriptions for the production of hydrogen cyanide from common chemicals. Personally, I've never had any luck at all with the industrial approaches starting with urea and sodium carbonate, and performed over a hot fire. I'm sure that it works, but control on the reaction variables and what values that those variables should be held at is difficult to determine. I've clearly smelled that wonderful almond smell in the crude product, but after isolation it was really just pure garbage.

From my standpoint, given the available precursors, the only logical method is potassium ferricyanide plus hot sulfuric acid and, as I have earlier in this thread described the ratios of reactants and concentration of acid and how I performed the reaction and over how long, I want to just share with you a few pictures of a successful run since there seem to be so many questions about the technique and not the actual chemistry.

In the heavily labeled picture below you can see the actual setup that I used. The exhaust tube simply runs outside via a port in my basement window. Mechanical stirring makes this reaction incredibly much easier to do than it is with magnetic stirring. The nature of the stirred mixture changes in a relatively complex way. The reaction mixture starts out as a spectacularly blue colored liquid which gradually changes to a heavy suspension which is evolving gaseous hydrogen cyanide. This can lead to substantial foaming and even the use of silicone anti-foaming agents is only moderately successful at minimizing this. The reaction becomes very much thicker eventually, almost impossible to stir, and then the material starts to become heavy and granular. Magnetic stirring works moderately well as long as you don't let the bar get stopped. Mechanical stirring does away with all of the difficulties. When foaming occurs, it can be easily broken apart to release the escaping HCN, and this greatly minimizes foaming. And the mechanical stirred doesn't get stopped no matter how thick the mixture becomes.

The picture of the solution which is bright blue is immediately after combination of the reactants. Within fifteen minutes the reaction mixture was beginning to change color as shown in the matching photo.

As I mentioned before, it's important to collect the hydrogen cyanide safely and so I distill it into a measured amount of water containing some sulfuric acid for stabilization. The receiver is also cooled in ice throughout the procedure as shown below. Also pictured is the device that I used to recirculate icewater through the condenser. It was scavenged from one of those medical devices that you use to cool an affected area, like a knee or an arm. I simply cut that part off and I have a well insulated reservoir with a built-in pump which runs on 12 V from a wall wart. This is much better than using tap water to cool your condenser. In fact I would not even suggest that as a viable alternative.

This run was performed just as the literature originally described it, no additives of any kind, no silicone, no copper salts. This was the first time that I actually used a thermocouple to accurately measure the reaction temperature. By the end of the reaction, the temperature in the pot was actually over 88°C. This was higher than I had estimated before. If you allow pot temperatures to rise this high, you'll need some relatively efficient means of separating hydrogen cyanide from water vapor. As you can see I used a Vigreaux with a vacuum jacket. I also monitor the temperature of the vapor at the top of the condenser and it never rises above the boiling point of hydrogen cyanide.

There are also two very short movie clips. One is a clip of the reaction mixture as it is just getting started. There is nothing particularly interesting about it, it's just a stirred blue solution. However some people have had questions about even this, and so I included it. The other short clip illustrates the maximum rate of hydrogen cyanide collection. This run produced 102 g which corresponded to a 53% yield.

I hope that some of you who are having difficulties in performing this procedure can take some useful information away from this descriptive account. Also, if you don't have the equipment to do it safely, don't try it. Cyanide antidote kits (and who has one anyway?) depend on you to be able to do IV injections (actually two) which has always astounded me, since many labs have kits and no instruction is provided in their use except by the manual. Imagine trying to hit a vein in an emergency situation....Oh, forgot to mention why you can't wait for the ambulance...it's because a likely injury is a cut with HCN in it or a largish inhalation. That is going to be way, way faster than ingestion of a salt. I'm not trying to scare you, but don't attempt this if you wonder if it's beyond your abilities.



Attachment: Initial Stirred Solution.mp4 (4MB)
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Attachment: Max Rate of Collection.mp4 (4.8MB)
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[Edited on 31-3-2016 by Dan Vizine]

Preparation of KCN via the Wagner Process as Modified by Engager - a carbothermic process

Introduction
I prepared KCN a few years ago using a modified Wagner process (ref 1). This process is based on the carbothermic reduction of potassium ferrocyanide.

K4[Fe(CN)6] + K2CO3 + C --> 6KCN + Fe + CO2 + CO

I didn’t post about this at the time as I thought it best not to advertise how to make alkali cyanides. Now I see that others have posted methods both on SM and YouTube. I think that the alkaline carbothermic methods, although more difficult, are inherently safer than those that generate HCN gas as an intermediate, especially for the underequipped neophyte. That is why I have decided to now post my preparation.

I struggled for some time to get success. But with guidance and encouragement from Engager I finally achieved a modicum of success. The following are my abridged lab notes.

Procedure
I weighed out the following:

•K4[Fe(CN)6]*3H2O (lab grade): enough to get 25.6g (8 parts) of the anhydrous salt
•K2CO3 (pottery grade): 8.36g (2 parts as Na2CO3)
•C(food grade activated charcoal): 0.64g (0.2 parts)

I dried the potassium ferrocyanide trihydrate and the K2CO3 for 1 hour at 145°C.

The ingredients were ground together in a mortar then placed in a 250 ml ceramic crucible with ceramic lid (a smaller crucible). This filled the crucible 1/3 full, as the charcoal was very light and fluffy.

This was placed in a muffle furnace and heated per the following schedule of Engager:

10:50AM……………12°C (room temperature)
11:25AM…………..600°C
12:30PM…………..600°C
12:45PM…………..650°C
1:45PM................... 650°C



After cooling, inspection showed there was some carbon and product on the underside of the lid (dried drops). The product was dissolved in 50 ml of boiling water that had been pre-boiled to remove oxygen. The solution was filtered into a 100ml RBF yielding a clear, slightly yellow filtrate. This tested strongly for cyanide using the Prussian blue test (see below).

Aspirator vacuum was applied to remove water. Bumping was a problem so a Claisen adaptor was added to increase head space. Clear crystals began forming on the bottom of the RBF with ~25 ml of liquid remaining. I then installed an ebulliator tube on argon to stop the bumping. This evaporation took a lot of heat using a hot air gun. This was slow going but did eventually remove most all of the water. Crystals on the tip of the ebulliator gave an intense Prussian blue! The crystals were very hygroscopic.

Prussian Blue Test Reagent for Detection of -CN
For the Prussian blue test the pH should be 5.5-6.5. Some Fe+++ ions must be present along with the ferrous ions. I dissolved some FeSO4*7H2O crystals in 1 ml of water then added 2 drops of 0.5M FeCl3. The ideal Fe:CN mole ratio is 0.5.

Clean Up
I cleaned up the equipment and workspace using an aqueous solution of laundry bleach (sodium hypochlorite) (ref 2).

KCN + NaOCl --> KOCN + NaCl

To test for residual –CN I swabbed my hood ss catch pan with Prussian blue solution. Only a slight trace of blue (-CN) was detected.

Transfer of the Crystals to a Storage Bottle
I slurried out the crystals in the RBF using denatured alcohol onto a filter paper in a7cm Buchner funnel. They were dried with a little sucked air flow. The weight of the crude crystal white KCN was 21.2g.

Assay of the Crude KCN Crystals
This was done using the Liebig AgNO3 titration method shown in Pierce & Haenisch (ref 3). The crystals assayed 36.7% KCN for a %yield of 28.7%.

References
1. http://www.sciencemadness.org/talk/viewthread.php?tid=23&...
(Engager’s post, bottom of p. 17)
2. Prudent Practices for Disposal of Chemicals from Laboratories, National Research Council et al (1983), p. 87.
3. Quantitative Analysis, by Pierce & Haenisch, 3rd ed (1951), p. 304.

Quote: Originally posted by Racconized

Hm the simplest way seems to be the ferrocyanide with a "weak" acid or diluted strong acid, the most appealing for me seems to be collecting the hcn into an alcoholic solution of NaOH.seeing that many nitrile synthesis from halide and an alkali cyanide uses water and alcohol it wouldn't matter if the resulting nacn is a bit wet right?

Quote: Originally posted by skip

I will never post my synthesis because of fear of repercussion.

Quote: Originally posted by aga

Dan, It is likely that the brand new users just read Wikipedia, hence the scant detail posted here. Unlikely that you're responding to people who actually do any Chemistry, much less likely anything related to Cyanides, highly unlikely they ever tried to make any. The vast majority of posts on this board over the past year are like this.

Probably eitherway it seems that this forum is dying put and sadly, it seems to be one of few chemistry forums around with active members. That's just how I see it though.
Anyway since cyanide is pretty dangerous or can be quite dangerous, are there any antidotes, which are legal (read somewhere amyl nitrates is a part of the official cyanide antidote kit however it's illegal and can be given without needles or with needle but IM instead of IV.

I can just google it but I feel like this is a more fun and keeps the thread active

Quote: Originally posted by Racconized

Quote: Originally posted by aga   Dan, Anyway since cyanide is pretty dangerous or can be quite dangerous, are there any antidotes, which are legal (read somewhere amyl nitrates is a part of the official cyanide antidote kit however it's illegal and can be given without needles or with needle but IM instead of IV. None that I know of. The irony of an illegal antidote is palpable. That is nearly as lame as reading that cannabadiol oil (which is NOT psychoactive, but DOES help treat a refractory form of epilepsy) was declared by the DEA to be a schedule I controlled substance. Seems that they need to find ways to justify their jobs, now that they won the war on drugs.

Quote: Originally posted by Racconized

Quote: Originally posted by aga   Dan, Probably eitherway it seems that this forum is dying put and sadly, it seems to be one of few chemistry forums around with active members. That's just how I see it though. I thought that I was finding a little less actual chemistry recently. I hope it's just a statistical blip, though. This is the best chemistry forum that I've found. Personally, if I didn't contribute here, I probably wouldn't anywhere. I'm not interested in being the smartest guy in a forum, and here, I'm not, by a long stretch.

Quote: Originally posted by Dan Vizine

Quote: Originally posted by Racconized   Hm the simplest way seems to be the ferrocyanide with a "weak" acid or diluted strong acid, the most appealing for me seems to be collecting the hcn into an alcoholic solution of NaOH.seeing that many nitrile synthesis from halide and an alkali cyanide uses water and alcohol it wouldn't matter if the resulting nacn is a bit wet right? Quite correct. And the cyanide is always in excess, so approximate weights are plenty good. When distilling HCN directly into cold, stirred base, EVERY SINGLE RUN THAT I EVER DID GAVE BROWN-BLACK POLYMERS along with the alkali cyanide. IN CONTRAST, collecting the HCN first and then adding it drop-wise to cold, stirred base gave a very pale brownish solution. I have no good explanation for the difference. [Edited on 18-12-2016 by Dan Vizine]

Found this in an 1897 text, titled "Manual of Chemical Technology":



Apparently, a mixture of KCN and NaCN can be easily prepared by melting 8 parts anhydrous potassium ferrocyanide with 2 parts sodium carbonate. Iron carbide precipitates from the melt.

[Edited on 11/9/17 by Melgar]

Quote: Originally posted by Hunterman2244

I made a test solution to test for any cyanide produced, and it showed positive, strangely it also was positive for sugar and potassium nitrate burned. Anybody know why?

Quote: Originally posted by Velzee

This probably occurs to a small extent as some of the sugar is reduced to carbon, and further reacts with KNO3.

Yes I tried it using Magnesium, it does work, but you get a lot of smoke, which is probably containing lots of cyanide.
I dissolved the cyanide using water, which left the Magnesium oxide and unreacted Magnesium. The filtered solution was able to dissolve Gold, so I would call it a success.
But I thought, the reaction between Sodium cyanate and Magnesium would be much less vigorous and you would need to constantly heat it, but it does burn quite fast and vigorous

Many paths involving exotic compounds (at least for the humble home chemists) and high temperatures have been presented.

How about the room temperature photolysis of NH3 and C2H2?

Here is the reference: 'Formation of hydrogen cyanide and acetylene oligomers by photolysis of ammonia in the presence of acetylene: applications to the atmospheric chemistry of Jupiter' by James P. Ferris, and Yoji. Ishikawa in J. Am. Chem. Soc., 1988, 110 (13), pp 4306–4312, DOI: 10.1021/ja00221a033, a link to the extract only available at https://pubs.acs.org/doi/abs/10.1021/ja00221a033?journalCode... , note suggested Equations (1) to (4). Interestingly, it is mentioned that the photolysis of CH4 can apparently lead to the formation of some C2H2 (more details on this path to C2H2 is available in the ebook 'Jupiter: The Planet, Satellites and Magnetosphere', edited by Fran Bagenal, p. 139 at https://books.google.com/books?id=aMERHqj9ivcC&pg=PA139&... ).

Also, 'cyano-containing hydrocarbons may act as photolytic sources for HCN and HNC in astrophysical environments' per http://iopscience.iop.org/article/10.3847/1538-4357/aa8ea7/m... .

Excuse me for not diving into details on just how just about 'anyone', not skilled in the art, could possibly photo cook a batch of a highly toxic gas. Somehow, I sleep better especially, if per chance, my windows are open!

Anyone performing photolysis experiments involving ammonia and hydrocarbons (like CH4) should, however, be advised to avoid smell tests, just in case .

[Edited on 10-7-2018 by AJKOER]

Quote: Originally posted by S.C. Wack

Why not zinc.

Quote: Originally posted by Mabus

Quote: Originally posted by S.C. Wack   Why not zinc. Don't have Zn powder yet. Also, an update on my iron adventure. I managed to dissolve most of the rust from the mixture with acid, and there is some blue precipitate there. Not much, but still significant, especially since the wool barely reacted. I guess the classical recipe works better.

Quote: Originally posted by PirateDocBrown

You can just buy Prussian Blue. Laundry bluing is just a suspension of it, get some, dry it in an oven. 3 bucks a pint, at my local Wal-Mart.

Unfortunately, CuCN (much easier to prepare than ionic cyanides) is not replacemet for K(Na)CN and it gives mainly isonitriles

Quote: Originally posted by Refinery

Could this process work: urea + sodium hydroxide + carbon in a furnace heated to reaction temp to produce cyanate and via carbothermic reduction to sodium cyanide + residual of sodium hydroxide? Then followed by purification with hot water, filtering, and crashing the sodium cyanide by adding ethanol which should reduce the solubility of NaCN to a significant degree, but still allow the remaining sodium hydroxide to stay dissolved? I prepared a batch of this by blending the three ingredients with blender and heating up. The solution was filtered, and adding significant amount of ethanol caused white crystals to precipitate in a very good amount. Should the product be mostly sodium cyanide that was produced? Unfortunately this process was done years ago and I had to get rid of my chemistry items due to changes in other life matters, hence no more info is available. The process described is from a german chemistry board. To obtain high purity an acid distillation for HCN to base could do the job, but if possible avoidable mostly due to the process being too laborous. (necessary safety disclaimer: im using A2B2E2K2 filter with the infamous breaking-bad yellow chemical suit and my workspace was located outdoors and I actually went so far as to build a 20-foot high chimney to my portable fume hood from 8" pvc tube to suck all nasties up to the sky.) [Edited on 10-10-2019 by Refinery]

Quote: Originally posted by kmno4

.... reaction ends at FeK2[Fe(CN)6] step (larger amount of H2SO4 will not help). Further conversion (to FeSO4) is terribly slow. Great dilution and boiling expels all HCN but with large amounts of water. You can add some CuCl (or even CuSO4) to the reaction mixure: it is converted to CuCN. It has so small solubility that FeK2[Fe(CN)6] is (slowly, on boiling) converted to CuCN (-> HCN). In this way all CN can be removed as HCN.....

My experience:

Theory

1mol urea (slight excess)
1mol NaOH
1mol C (slight excess)
= 1mol NaCN

Urea + NaOH = NaOCN (+ NH3 + H2O)
NaOCN + C = NaCN (+ CO)

It appears that urea and carbon can be excessed because the other one dissipates and the other one remains inert, easily filtered, but sodium doesn't go anywhere.

Cyanuric acid is very slightly soluble (1/100), cyanate 10/100 and cyanide 60/100. For ethanol, the solubility crashes to almost zero at 100% and to 2% at 95%. 50-70% ABV crashes out major amount of NaCN from water. When water is added, it dissolves cyanide, cyanate and other stuff, but carbon and possible cyanuric acid remains and is filtered. When alcohol is added, cyanide crashes out and is filtered.

Carbon is powdered using blender, and reagents are poured in SS crucible with gravity plug. Crucible is placed in ceramic wool round kiln and heated using high power propane torch. The plug audibly rattles when NH3 and water evaporate. Rattling stops eventually, heating is continued. Crucible will eventually visibly start to glow dark and then cherry red, and rattling begins again and visible jets of yellow flame are visible between the plug. When jets of flame cease, heating is stopped and crubile is left to cool. Water is poured in (100mL for each 50g of NaCN theory; 60g/100mL sol @ 25C). A lot of mechanical work is required to dissolve the concrete-like residue and a crucible with large opening is strongly preferred for this process. When most to all is dissolved (which took total of 12 hours + lots of mechanical work), the black gunk is filtered into clear, slightly yellow liquid.

1.4x volume of 95% EtOH is added. At first, two layers are formed(a mystery?), a lower, yellowy, and upper, cloudy white, but it quickly dissipates upon stirring, and liquid turns cloudy. Liquid is filtered again, and an amount of very slightly yellowish mass is collected and placed on a drying pan. No final weighting has been made yet, but the yield appears to be over 50% with a margin. No tests for purity has been made yet.

Notes:

- Some crystals crashed out from filtered residues after NaCN was recovered. Cooling and refiltering the residue could increase yield.
- All residues and equipment were treated with calcium hypochlorite and rinsed thoroughly with running water after the process. Proper PPE with full face mask and ABEK filter were used. Care was taken not to breath any fumes emitted during heating or other phases and process was carried outside to eliminate any contamination or ventilation issues.
- If working routinely with cyanide, cyanokit (hydroxocobalamin) must be kept at person in order to reduce lethal effect if an accident, for ex. a spillage occurs.



[Edited on 11-6-2020 by Refinery]

Quote: Originally posted by Polverone

The above text says that the Beilby cyanide process once provided half of the world's cyanide demand, yet there are only two unique references to it on the whole web, one from the Sciencemadness Library and another from the Digital Library of India.

My first crystals of potassium ferrocyanide.
By the KOH+urea method, in 3 steps.

Quote: Originally posted by Calculon

My first crystals of potassium ferrocyanide. By the KOH+urea method, in 3 steps.

Pray tell how!

Quote: Originally posted by Fyndium

The carbonate can be replaced with hydroxide

Quote: Originally posted by Fyndium

When dissolved in water and crashed out with plenty of ethanol, one should wait a good time before filtering the solids, because the process takes some time.