Sciencemadness Discussion Board

Preparation of cyanides

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Dan Vizine - 20-9-2015 at 07:00

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.

  1. Combine 100mL distilled water with 100mL H2SO4. This reaction heats the dilute to 100C. Therefore wait for it to cool back to room temperature
  2. Add 211g K4FE(CN)6 trihydrate to 1 liter boiling flask.
  3. Add 200mL water and begin stirring. (This requires a more powerful stirrer).
  4. Add the cooled 200mL H2SO4 dilute to boiling flask.
  5. Heat solution to 60C.
  6. Run for <i>four hours</i>. <B><I>Nothing</B></I> evolved!
  7. 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.
  8. 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]


Regarding A)
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. The ~ 60 C blue mixture foams during the first hour when HCN evolution is fastest. Thereafter the mixture seems to thicken and the bubbles are very tenacious. Heating can then be increased (above 60 C) if desired, but this can bring over more H2O. I add Dow Corning anti-foam agent and it may help a little. I find that it is necessary to watch the process closely throughout as stirring speed needs frequent adjustment. Are you always able to keep the suspension actively stirring? Don't confuse the sound of a rattling, but stuck, stir bar with one that is stirring. Sometimes it's necessary to glimpse the stirring magnet of your stirrer, just to know if it's working, or not (spinning very fast as it decoupled from the stirring bar which was formerly stirring a thick bubbling slush and so had the stirring plate set rather high to provide the needed torque).

P.S. See the above answers re. my use of copper metal instead of CuCl. It may have helped, it certainly didn't hurt.

And B) HCN, water, sulfuric acid are mutually miscible in all proportions.

I still strongly suggest a heating source that completely surrounds the flask, an oil bath is the easiest, cheapest soln.

[Edited on 20-9-2015 by Dan Vizine]

lysander - 20-9-2015 at 15:48

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]

Dan Vizine - 20-9-2015 at 16:26

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.

lysander - 20-9-2015 at 16:43

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 my first two tests were with ferricyanide. Then since all other sources indicated ferrocyanide, and with the same specifications, I used that for #3-5.

Meanwhile, I combined and ran a single distillation of the fractions from all runs to date. Most of the liquid boiled about 30C as expected, producing 50mL of condensate. The "other immiscible stuff" remained in the boiling flask, so I poured it over a thin layer of NaOH. It reacted violently. I put the resulting deliquescent mass in a freezer and might try to assay it further sometime....

[Edited on 21-9-2015 by lysander]

lysander - 13-1-2016 at 18:31

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?

elByDnI.jpg - 419kB

Heavy Walter - 14-1-2016 at 07:44

Hi

See this:

http://www.ehs.wisc.edu/chem/GlasswareCleaning.pdf

Dan Vizine - 31-3-2016 at 12:43

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.

Set-up.jpg - 139kB Cooled Receiver.jpg - 76kB Blue Color.jpg - 2.8MB Initial Color.jpg - 1.8MB Ice Water Re-circulator.jpg - 999kB

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]

Magpie - 31-3-2016 at 14:20

I knew HCN could be made using acid but felt the alkaline heating method was less risky. I struggled with the alkaline heating method for quite a while. With the help of Engager I was finally successful. I agree that the way you have done it is sensible if you have the right equipment and know what you are doing.

I can't open your movies. What software is required?

Dan Vizine - 31-3-2016 at 19:24

Hi Magpie,

I tried the alkaline method one time about 20 years ago. It was not a very successful attempt. The idea of the preparation being the purification method also was what appealed to me about the acid method.

Most any player, even WMP should play them. VLC player is an open-source freeware download and excellent with many formats. The first video is trivial. The second shows a peak production rate of a little better than 1 drop/sec.

Magpie - 2-4-2016 at 12:14

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

250 ml crucible.jpg - 110kB

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.



clearly_not_atara - 4-4-2016 at 09:50

http://www.nrcresearchpress.com/doi/abs/10.1139/v61-169#.VvB...

Can someone download this paper? If the reaction generalizes to glyoxylic acid it would be

CHOCOOH + NH2OH >> CO2 + 2H2O + HCN

Reaction occurs in water.

EDIT: Thanks, gdflp! The paper indicates that both glyoxylic acid and mesoxalic acid will give HCN by reaction with hydroxylamine. However only the anti oxime decomposes at room temperature.

[Edited on 4-4-2016 by clearly_not_atara]

gdflp - 4-4-2016 at 10:05

Here you go.

[Edited on 4-4-2016 by gdflp]

Attachment: v61-169.pdf (731kB)
This file has been downloaded 545 times


skip - 4-4-2016 at 16:49

I've made sodium cyanide so many times it's not funny. About every time was at least a mole, using HCN. Over the years I've probebley made a few pounds, perhaps more. I've never had any issues, even gotten it on my fingers(washed off right away). I will never post my synthesis because of fear of repercussion. The first time I tried the synthesis I was scared to death and had a scuba mask on, as I gained experience the mask is gone and my fear of cyanide considerably diminished . Now the HCN liquid is no joke, respect that stuff and protection is a must. It can be handled though if you have good lab skill. Yea its deadly stuff but I think people freak out about it.

testimento - 6-4-2016 at 09:57

I have understood that using urea instead of ferrocyanide is much more cheaper and OTC method for producing alkali cyanides. The process involes about molar ratio of urea and sodium carbonate with one mol of reductive carbon heated to 800-1000C for the reduction to take place. I performed a test with these at small scale years ago, but I couldn't confirm if cyanide was produced, or how pure it was.

Chiron - 8-4-2016 at 13:03

Polverone, I admittedly did not read the entire thread, just the first few pages. I'm not sure if it has already been mentioned but did you ever consider using methanol instead of water for the evaporation component of your experiment? Cyanide salts dissolve less readily in CH3OH and it has a lower evaporation point than water. Heat will generally speed up the reaction with the air to form cyanate, but at least with a lower boiling point that would be reduced.

I guess hypothetically you could use a distillation setup to remove the methanol without air exposure to the cyanide, but would that much cyanate be produced if you boiled it openly anyway?

chemplayer... - 9-5-2016 at 06:29

Tried out another cyanide preparation today; this time using potassium ferrocyanide and fusing with potassium carbonate.

https://www.youtube.com/watch?v=E8lULpuQvg4

We'd tried this before using potassium ferrocyanide and sodium carbonate and had terrible results, so we were expecting the worst, especially as our spare kitchen gas burner is on the brink of dying (too many aluminium chloride preps!).

Anyway, to cut a long story short it was surprisingly effective. We managed to isolate just over a gram of crystalline solid which according to the tests we've done so far seems to be fairly pure potassium cyanide (but this is 18% yield). Getting the rest of the product out of the aqueous solution is much harder using this method. But a lot more OTC than using sodium metal, so may be of interest...

skip - 9-5-2016 at 17:40

love you're video's . very good work. cheers mate.

Racconized - 18-12-2016 at 06:08

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?

Dan Vizine - 18-12-2016 at 11:41

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]

Dan Vizine - 18-12-2016 at 11:58

Quote: Originally posted by skip  
I will never post my synthesis because of fear of repercussion.


I hear statements like this from time to time. I assume that the repercussion you fear is a liability-based one?

It makes me wonder. If Wikipedia tells me how to make cyanide or bromine or whatever, could I reasonably expect that the same would be true? Could I expect that a court would hold them liable if I hurt myself? Common sense says no, but of course, the law is whatever the lawyers can convince the judge or jury is true.





[Edited on 18-12-2016 by Dan Vizine]

aga - 18-12-2016 at 12:33

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.

Racconized - 19-12-2016 at 14:36

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 :)

Dan Vizine - 20-12-2016 at 08:38

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.

Dan Vizine - 20-12-2016 at 08:49

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.

Racconized - 20-2-2017 at 05:23

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]


How about the yields, what have you been able to get (average). Is the yields worth dying or almost dying for (Just joking, kinda). Or should I just buy it (100g for 30usd)

Dan Vizine - 20-2-2017 at 09:32

I'm a chemist by trade. Thus, if a starting material is available for purchase, I'll almost never make it. Why waste time on starting materials or reagents unless you have to. And that is a good price.

Yields have been around 50-55 %. You can never say for sure. Some water vapor is carried over with the HCN just by entrainment.

clearly_not_atara - 1-9-2017 at 14:58

Could you trans-ligate ferricyanide to ferrioxalate? I.e.:

K3Fe(CN)6 + 3 K2C2O4 >> K3Fe(C2O4)3 + 6 KCN

If not, are there some other ligands that might accomplish this? Wikipedia claims that the anion FeF5H2O(2-) is very stable, so that would be:

K3Fe(CN)6 + 5 KF + H2O >> K2FeF5H2O + 6 KCN

These methods may avoid producing any HCN if you're careful, although you then need to precipitate cyanide, unless you want to convert it to thiocyanate in situ, which might be possible somehow.

[Edited on 1-9-2017 by clearly_not_atara]

clearly_not_atara - 1-11-2017 at 17:14

A-ha!

"Formaldoxime readily decomposes into its nitrile (hydrogen cyanide) and water when it is heated with aqueous alkalis"

Dunstan & Bossi, Proceedings of the Chemical Society Vol 10 no 136, "Formaldoxime", attached.

This method is nearly perfect. There are no side products, the precursor formaldoxime is easily prepared from formaldehyde and hydroxylamine, and the cyanide is produced in alkali.

Attachment: dunstan1894.pdf (1.5MB)
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Melgar - 9-11-2017 at 01:45

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

kcn-nacn.png - 608kB

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]

The Volatile Chemist - 9-11-2017 at 21:42

I think I saw the above method in a Cody's Lab video. I've wanted to try it before, and might soon. Also, Iron carbide, hmm...

Hunterman2244 - 18-6-2018 at 19:14

Sorry for bringing the thread back up, but I did a rough test of the burning carbon/KNO3 method, and it seems promising. Has anybody else done this, or know the best ratios?

Hunterman2244 - 25-6-2018 at 16:18

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?
The gunk left over from the reaction was dissolved in water and filtered to get the cyanide, it may leave some kno3 in solution, but for the moment its good enough.
The test solution was made by putting and iron nail in sulfuric acid and adding some h2o2. Dripped into the cyanide solution, it creates a definite prussian blue.

Velzee - 26-6-2018 at 17:14

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?


There is a lesser known reaction between KNO3 and C that indeed forms KCN;

\[KNO_3 + 4C \rightarrow KCN + 3CO\]

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

Hunterman2244 - 27-6-2018 at 04:42

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.

It seemed a lot stronger a reaction in the test. The blue showed up faster. The amount of sugar and kno3 I burned was also less.

walruslover69 - 27-6-2018 at 05:59

Has anyone had any luck with reducing cyanate to cyanide by aluminum, magnesium or zinc?

Tellurium - 27-6-2018 at 23:00

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:o

walruslover69 - 28-6-2018 at 06:44

I did some quick calculations,

3NaCNO + 2Al ---> 3NaCN+ Al2O3 = -780 kj

NaCNO+Mg ---> NaCN+MgO = -287 kj

NaCNO+Zn ---> NaCN+ZnO = -39 kj

I might try and see how the zinc and aluminium reductions compare.
Sodium cyanate can be made from store bought cyanuric acid very cheaply so it could be a very practical method.


clearly_not_atara - 9-7-2018 at 14:43

It seems likely that in basic solutions isonitrosoacetone would decompose to acetyl cyanide, which is typical of aldoximes in alkali, and thereafter to cyanide anion and acetate:

https://pubchem.ncbi.nlm.nih.gov/compound/Isonitrosoacetone#...

As is typical for other ketones this compound should be produced by nitrosation of acetone.

AJKOER - 10-7-2018 at 04:31

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]

Mabus - 20-1-2019 at 07:32

My latest attempts at making KCN by reducing KCNO made from urea and KOH were terrible.
For the first batch I tried using Mg powder, which worked, but I think it worked too well, since I only got a few grams of Prussian blue from the mixture, when the theoretical yield should have been like 40 g or so. I'm pretty sure what happened there is that the magnesium metal stripped away not only the O from the KCNO, but also the N from the molecule, leaving behind a very hot potassium carbide, which oxidized in air producing a very nice purple flame, to form lots of potassium carbonate (which crashed out beautifully from the methanol I used to extract the cyanide from the mixture).
A second attempt, using Al powder failed miserably, and even when I used a torch to directly ignite the mixture, all that happened is that the mixture melted, and nothing else. Adding a small amount of magnesium powder to act as a starter failed to do that, and it would appear that Al powder just doesn't work.

I also tried a different approach, to make Prussian blue directly, I heated together a mixture of KOH, urea and some steel wool, mainly because last time I cleaned the SS cup from the KCNO leftover, I noticed a small amount of Prussian blue forming on the center of the bottom of the cup, where the temperature would be the highest, so figured that maybe making Prussian blue might work better. After the solid cooled, I took it apart, but didn't see any blue formations, figured I'd either have to use a different form of iron or simply the temperature wasn't high enough. Upon addition of acid however, I noticed that the solution has turned black, but it also has a weak dark blueish hue, and it's not the soluble part, but rather from the suspensions. I think I might have got some Prussian blue, but it's very little, although I'll only know more after I've purified the whole solution. If this works, I might try using iron powder or turnings next time, and also use higher temperatures.

S.C. Wack - 20-1-2019 at 10:17

Why not zinc.

Mabus - 20-1-2019 at 12:27

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.

PirateDocBrown - 11-2-2019 at 08:51

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.

Felab - 12-2-2019 at 12:25

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.


You can make zinc powder by electrolising sodium zincate, which is where I get mine. NurdRage has a great video on this: https://www.youtube.com/watch?v=3X9c6epL7HQ

morganbw - 12-2-2019 at 16:24

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.


I will state that I did not know this and that I will be looking into it as well.
Thank you.

S.C. Wack - 12-2-2019 at 17:08

Zinc is everywhere. You can get it for pennies if you have a ball mill or iron mortar. I had no problems with the powder in fresh alkaline batteries as long as it was well washed free of alkali; dilute acid might help. Expensive when compared to the preferable fine powder sold by pyro suppliers for Zn/S rockets.

PirateDocBrown - 15-2-2019 at 08:09

For Zn, look for pyrotechnic suppliers. Last I got some, it was $8 a pound, powdered.

And you can get it FROM pennies, if you wanna go that way. Just melt some in a crucible, and pour into water, to make mossy zinc. It'll have some Cu contamination, but it'll be good for most purposes.


[Edited on 2/15/19 by PirateDocBrown]

clearly_not_atara - 15-2-2019 at 10:29

If you make CuCN from Prussian Blue as described in this old thread, could you then use a solution of CuCN in MeCN as a source of nucleophilic CN-? I.e. something like this:

CuCN + 4 MeCN (solv.) >> Cu(MeCN)4+ + CN-

CuCN + EtBr + excess MeCN >> EtCN + Cu(MeCN)4+ + CN-

Or, possibly, perhaps you could even precipitate KCN from this solution by adding KI?

[Edited on 15-2-2019 by clearly_not_atara]

kmno4 - 15-2-2019 at 12:59

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

Refinery - 10-10-2019 at 13:27

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]

Mabus - 16-10-2019 at 11:58

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]

Yes, it works. The urea+NaOH+C part. Not sure about crashing the NaCN with EtOH though. I know it doesn't work with iPrOH since the alcohol gets salted out of the solution.
Unfortunately, the biggest drawback of using urea is that the yield is pretty bad, I never managed to get past 20%, half of the nitrogen is lost in the reaction as ammonia, and then half of the rest simply breaks down during the reduction due to side reactions.

kmno4 - 10-6-2020 at 11:40

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.....

Because I used almost all my NaCN, I decided to verify the "CuCl" way. Indeed, I was able to convert all CN into HCN and absorb it in KOH-EtOH solution. It is good method allowing to convert practically any CN containing material into HCN. Two important remarks:
1) amount of H2SO4 should be taken with (at least) 10% excess, counting on bisulfate formation (it means KHSO4 from K4[Fe(CN)6] for example, not K2SO4 - the solution must be highly acidic to prevent slow reaction rate
2) few (~5 g) grams of NaCl or KCl per ~20 g K4[Fe(CN)6] should be additionally added - it greatly speeds up reaction
The rest of information can be found in "Chemistry of cyanogen compounds" by Williams, on pages 278-279 and additional references given there (two papers - available from the net)

Refinery - 11-6-2020 at 10:32

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.

dryis.jpg - 111kB emiss.jpg - 16kB

[Edited on 11-6-2020 by Refinery]

kmno4 - 16-6-2020 at 13:13

Quote:
Because I used almost all my NaCN, I decided to verify the "CuCl" way (...)

Another tested variation of this method below.

To decrease H2SO4 consumption, the reaction is performed in two steps. The first step is reaction of H2SO4 and K4[Fe(CN)6] (in water) only. This leads to insoluble K2Fe[Fe(CN)6] as end by-product, but amount of the acid is calculated (+ 10% excess) for K2SO4. No matter how much more H2SO4 is used, K2Fe[Fe(CN)6] is very resistant to it.
When most of HCN distilled off*, the post-reaction mixture is set aside and cooled to r.t. Transparent liquid is the pipeted out as much as possible and to the remaning "mud" of K2Fe[Fe(CN)6] another portion of H2SO4 solution is added (calculated for KHSO4 formation). Instead of CuCl, CuCN is added, but in this case slightly larger amount of NaCl should be added. Fortunately, for this purpose CuCN does not have to be pure.
It was observed that K2Fe[Fe(CN)6] is rather easily oxidized by air (it becomes blue), especially in the second step (which lasts much longer that the first one) and it seems to slow down its decomposition.
To prevent this, Cu tiny wire (from old coax) is added in amount of ~2 g (or more, per ~20 g of ferrocyanide). The excess of it remains in exhausted, green transparent solution. It is easy to see that some part of it really reacted (acted as reductor).

* in the end of reaction, HCN goes off with lage (> 90%) amount of water. Optionally, it may be collected separately and added to the mixure in the second step. It sligtly increases the KCN yield, because KOH ethanolic solution is less diluted with water.
See diagram of vapor-liquid for HCN-H2O system here:

Code:
http://www.ugr.es/~tep028/pqi/descargas/Industria%20quimica%20organica/tema_1/documentos_adicionales/a08_159_cianhidrico.pdf


Fyndium - 9-9-2020 at 11:24

http://www.sciencemadness.org/smwiki/index.php/Sodium_cyanid...

Few questions:

- Doesn't the reaction of cyanate and carbon produce carbon monoxide, not dioxide? At least in the reaction a flame was emitted from the crucible for the expected duration, and afterwards almost all carbon was gone. Carbon dioxide does not burn, to my knowledge.

- Since sodium hydroxide is reacted with cyanuric acid to form eventually sodium cyanate, there should be little to almost none left, especially if a slight excess of urea is used, because it should completely decompose upon enough heating?

- Why use magnesium thermite reduction, when carbon does the same?

I made what is presumed to be sodium cyanide via the sodium hydroxide urea carbon method, and when the reaction was complete, the cake was dissolved in hot water, carbon was filtered to result a yellow solution, which was mixed with equal volume of ethanol to precipitate white mass, which was filtered dry and dried and presumed to be mostly cyanide.

Edit: also regarding the wiki page about purification by HCN distillation, should it be possible to remove carbon dioxide by condensing the HCN into liquid form through a reflux condenser, form where it would drop into NaOH solution and CO2 would vent out and only trace amounts would travel down into NaOH solution? For the record, the vented gas from condenser would of course be led through a long tube into a safe exit. I'm not sure how to appropriately determine when the solution has been depleted from NaOH other than installing a syringe outlet to determine pH of the solution and cease the generation when the solution does not show up as basic anymore. Also a third inlet with dropper funnel to add more hydroxide could be placed. I presume this method would produce mostly highly pure sodium cyanide?

[Edited on 9-9-2020 by Fyndium]

Fyndium - 8-10-2020 at 12:43

Well, it seems that no one has any knowledge of above. Or am I the only one with access to facilities suitable for making this stuff?

I found out last time that the yield I acquired was partially cut by hesitating with the filtering process. It seems that when adding in ethanol, one should wait for good 15 minutes to allow the cyanide to settle. When I filtered it by vacuum, more kept crashing out and I found out the solution I dumped contained quite a lot of white mass.

What I'm yet to figure is that is there CO2 formed at some point? My observations suggest that it indeed is the monoxide that is produced, because an intense flare was emitted from the vessel exhaust tube and almost all of the carbon was gone when the cake was dissolved an filtered off from it. Because if there is no CO2, any residual sodium hydroxide should pretty much stay in the solution when crashed.

What'd be the most effective way to determine the approx purity of obtained cyanide?

njl - 8-10-2020 at 14:28

Double displacement in aqueous solution with silver nitrate.

Pumukli - 9-10-2020 at 10:38

Distilling HCN into aquaeous NaOH is not a preferred method because those who tried it reported dark, discoloured product.

Calculon - 16-11-2020 at 18:42

Someone tried the patent WO2016199944A1 ?

The method seems pretty simple, sodium carbonate + urea + additive1---> CYANATE--->reduction---> CYANIDE
I think is missing the step of separation of ammonium carbonate after first order reaction (it's necessary ?) and the addition of coal is missing in the step for second-order reaction (reduction).
Infact in the process flow diagram is showed the addition of an unknown "additive 2"


Fyndium - 19-11-2020 at 02:31

The sodium carbonate, urea and carbon process is well reckoned here. There was mention that it has somewhat lowish yields and there will be impurities.

The carbonate can be replaced with hydroxide, and there should be little carbon dioxide contamination, as carbothermic reduction produces carbon monoxide, which can be seen burning at the exit hole.

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. I noticed a good bunch of white residue in the filtrate when discarding it, but had no time to refilter it anymore.

Calculon - 20-11-2020 at 12:47

Due to the low yield of the sodium carbonate, urea and carbon process I wanted to try the patent
https://patents.google.com/patent/WO2016199944A1/en

same process but good yield, that claim a content of sodium cyanide in the raw obtained product is 62-68%, it's a lot!
And after this step i can use the usual method, dissolve "metal" in water and crashed out with ethanol (i usually wait 6hours before filtering the solid out of ethanol solution at 0°C)

Fyndium - 20-11-2020 at 13:09

I'm still yet not sure if NaOH is better option as sodium source than Na2CO3. If there will be no carbonate present and if no CO2 is evolved at any given time, it should not be in the final product. I'm not sure about reaction kinetics, though.

S.C. Wack - 22-5-2021 at 11:43

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.


BTW the patent is also known as US484579. It's interesting on the semi-professional scale, once some MCN has been obtained by other means to use as flux. The starting charge illustrated there is 20% KCN, 20-25% C, remainder K2CO3; mp below 850C. I wonder where the mp of the Na version or mixture with K is.

Calculon - 27-10-2021 at 13:23

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

1ab.jpg - 806kB 1bb.jpg - 1.1MB

Fery - 27-10-2021 at 20:26

Calculon - well done and beautiful crystals !!!
Could you please post more details about your experiment? It would be very useful for other chemists.

artemov - 28-10-2021 at 01:39

Quote: Originally posted by Calculon  
My first crystals of potassium ferrocyanide.:)
By the KOH+urea method, in 3 steps.



:o Pray tell how!

Calculon - 29-10-2021 at 15:48

I still need time to do a lot of tests to improve the yield, the reaction is very simple but I think that the details make the difference.
For this reason now at the end of the reaction I convert the KCN into potassium ferrocyanide, it's more stable and easier to separate to weigh it and measure the yield.
Actual yield 15g KCN every 100g KOH
If anyone knows any tricks i can test it, however my schematic procedure is as follows:

1° step KOH + urea ==> KCNO
250-300°C for 30 minute in a SS large pot (5L) until all the water and ammonia have evaporated, mix strong meanwhile as it cools off to avoid the cyanate from sticking to the bottom like concrete. Put this grainy powder in a mixer till finely powder, avoid contact with wet air as much as possible.

2° step KCNO + C ==> KCN
Mix activated carbon finely powder ( I make from sugar, also charcoal works) with the crude cyanate into the mixer and chop for a few minutes. Avoid contact with wet air as much as possible, and put in a oil filter jar up to 50% of the volume, close well with a sheet metal lid and aluminum foil to prevent air from entering.
I use a homemade gpl furnace, start to heat slowly 200°-300°-350°C for the first 30-50 minute until the smell of ammonia stops, now raise the temperature to medium 450°-550°C (the bottom of the jar is dark red) for 80 minute, little blue flames (invisible on daylight ) come out of the lid, when the blu flames are disappearing raise the temperature to 700°-800°C (the aluminium foil fuse) for 30 minutes.
Switch off the flame and let cool without open the lid. Now the "metal" is more hard than concrete need hammer to crush it together with the pot.

3° step KCN + Fe ===> K4[Fe(cn)6]
Put the product with all the iron pieces of the oil filter into a glass beaker and add distilled water (the smell is like H2S), heat to 50°C for some hours stirring sometimes, leave to rest for 48 hours stirring occasionally, filter, concentrate and separate the ferrocyanide using the temperature solubility curve (very complicated). First forming a lot of white crystals are K2CO3 i think, instead ferrocyanide accumulates in the solution up to a certain point start to make yellow powder or slurry crystals, now take the concentrated solution and add slowly HCl till stop bubbling CO2 to ph 8-9 (not less otherwise Prussian blue is formed, it can be seen when the drops of HCl are dropped), make saturated solution at 30°C , filter, and leave alone for 24 hours. Crystals will be formed.
Dissolve again the crystals in distilled water, make saturated solution at 30°C, filter, leave alone for 24 hours, and beautiful big crystals will be formed.

This is only a procedure without many details and doses, i will post when i have a better yield.






S.C. Wack - 30-10-2021 at 09:22

The solubility of K ferrocyanide is an example of common ion effect, e.g. a precipitate starts to form in seconds when KCl is added.

Quote: Originally posted by Fyndium  
The carbonate can be replaced with hydroxide


There's probably a good reason why all the chemists of yesteryear never use 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.


A few cpds. mentioned in this thread are not entirely stable in alkaline water.

Lionel Spanner - 12-8-2022 at 03:52

Given that ChemPlayer obtained sodium and potassium cyanides by reducing potassium ferrocyanide with molten sodium metal, has anyone tried the same with Prussian Blue?
If it works, the reaction should go as follows:

Fe4[Fe(CN)6]3 + 18 Na ---> 18 NaCN + 7 Fe

[Edited on 12-8-2022 by Lionel Spanner]

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