Sciencemadness Discussion Board

Making Sodium Cyanide

ScienceHideout - 17-9-2011 at 16:48

Hello everyone!

I am planning a reaction on making NaCN from NaOH and urea. This will prevent the scary encounter with HCN.

My thinking is to add NaOH in a test tube, and add a stoiciometric amount of urea. I will heat this in a fume hood with a bunsen burner.

Here are where my problems come in-
Will the NaOH safely react without eating the glass?
What IS the stoiciometry between these substances?

I don't have too much experience with urea, and all my molten NaOH I've encountered before I used steel. Any thoughts?

Thanks in advance!

hkparker - 17-9-2011 at 17:07

Please be careful, and reconsider trying this.

What is your source that NaOH reacts with Urea to form NaCN? Another thread perhaps? If you saw a source then I'm sure they gave you a reaction, from which stoichiometry could be calculated.

I've looked around online and cant find a reference for this. From a google result I get:
Quote:

The hydrolysis of urea proceeds like normal base-catalyzed amide hydrolysis, giving first sodium carbamate and ammonia. The carbamate readily undergoes a second hydrolysis reaction to give sodium carbonate and another equivalent of ammonia.


Not NaCN. This was in reference to a (I believe wet) reaction between urea and Sodium Hydroxide. <a target="tab" href="http://www.scienceforums.net/topic/38367-what-happens-when-you-add-sodium-hydroxide-to-urea/">Link here</a>.

Also, molten NaOH eats glass fast, so it could not be done in glass.

ScienceHideout - 17-9-2011 at 17:10

I have heard of people doing the same with KOH, and I know that is MUUCH more corrosive than NaOH.

hkparker - 17-9-2011 at 17:12

How is KOH more corrosive then NaOH? At least, "MUUCH more corrosive"?

Once again, where did you hear people doing this?

Endimion17 - 17-9-2011 at 17:19

Molten sodium hydroxide eats glass for breakfast. Urea, if heated alone, yields something I despise - a mixture that is nearly impossible to remove. AFAIK, it contains cyanuric acid, biuret and some polymerized stuff. Essentially, you get an almost inert, rock hard polymer that ruins glassware. You can pound it with a hammer if you like.

I have no idea whether that polymer is soluble in molten sodium hydroxide. But glass is, so chances are your tube will be gone before urea.
I don't really know will urea gently dissolve in molten NaOH, to give a homogenous reaction mixture.
And I don't recall cyanides having to do anything with this.

[Edited on 18-9-2011 by Endimion17]

ScienceHideout - 17-9-2011 at 17:22

I read on this forum of a person claiming that he did this reaction with KOH. The topic was about him claiming that KOH is less corrosive than NaOH, but from experiments and knowledge I know otherwise.

hkparker - 17-9-2011 at 17:30

A link it what I had in mind. But looks like s/he was wrong, this won't work. And KOH is not more corrosive in a any significant way that I know of. It is slightly more soluble, so there's that, but the potassium ion is larger and I would image less % of KOH is actually hydroxide ions then NaOH.

ScienceHideout - 17-9-2011 at 17:39

http://www.sciencemadness.org/talk/viewthread.php?tid=15633

Sodium Hydroxide is stronger than lithium hydroxide, but not as strong as rubidium hydroxide, so potassim hydroxide would be stronger than sodium hydroxide, right?

hkparker - 17-9-2011 at 17:46

Thanks for the link. Read the whole thread. blogfast25 points out how in solution KOH is only slightly more corrosive (Im guessing because K+ is a weaker conjugate acid?). However, <a target="tab" href="http://www.springerlink.com/content/n5523871x634l523/">this link</a> says that NaOH is more corrosive specifically to glass.

Either way, The thread says heating KOH and Urea with cyanuric acid will make KOCN (no source backing it up). Doesn't mean NaOH and urea will make NaCN if thats what you were going off of.

ScienceHideout - 17-9-2011 at 18:04

Well, chemical reactions tend to go in 'families'. example: you can make fluoroform, chloroform, bromoform, and iodoform all with the same reaction, but different reactions.

BTW: I realized just then he said cyanate, not cyanide.... but NaOCN would still be as useful.

hkparker - 17-9-2011 at 18:31

For what? Whats your goal with making cyanide/cyanate?

plante1999 - 17-9-2011 at 18:35

Does anyone already make the famous polymeric material from pyrolisis of urea , if yes does it melt , I Supose it is melamine. Simply by curiosity , I also want cyanide for making gold sol.

Formatik - 17-9-2011 at 22:14

Cyanate can be obtained by route of alkali base and urea, but decomposition of it (at least for KCNO) only gives partial yield cyanide at higher temperatures. This and cyanate preparation was mentioned here.

I mentioned my experience of attempting to obtain cyanate here, but for some reason got something containing cyanide, even though I was only using a bunsen burner to heat, and I believe used stoichiometric amounts.

If you are heating aq. NaOH, Na2CO3, etc. with urea, then you will split off all nitrogen as NH3. I've done this as well (primordial chemicals thread).

ScienceHideout - 18-9-2011 at 06:06

I am planning on making a little bit of cyanate/cyanide salt for synthesis of inorganic (and some organic) compounds. I always love adding another polyatomic ion to my lab. :cool:

Heating sodium carbonate seems a lot easier than hydroxide- but- it always seems like it would be difficult to melt- especially because it is so... dry! I've melted many a chemical before, but, alas, CO3^2's weren't one of them!

I guess I could try the alkali carbonate... again I know that I will not get a good yeild, but I might aswell try! That's why it's called an experiment!

I will post my results!

barley81 - 18-9-2011 at 07:19

There's a whole thread on cyanide preparation here:

http://www.sciencemadness.org/talk/viewthread.php?tid=23

The process involved fusing alkali carbonate with urea/cyanuric acid (giving cyanate), adding charcoal and heating to red heat or higher (producing cyanide and CO), dissolving/filtering the residue, and precipitating with alcohol.

Relatively pure (at least free-flowing) potassium carbonate can be bought cheaply from pottery supply stores if you want to make KCN and don't want to use more expensive KOH.

For high temp. stuff, you can make a crude furnace from an empty paint can, a hairdryer, and cheap charcoal briquettes. It worked for me for some crude aluminum casting.

Don't use glass as your reaction vessel with the furnace, it may crack. Use a metal crucible (a soup can, an iron pipe cap/nipple, or a stainless steel cup).

Also it is very, very, very, very helpful to use the search function before starting new threads.

[Edited on 18-9-2011 by barley81]

ScienceHideout - 18-9-2011 at 09:47

Thanks so much! I will let you know of my results...

cyanureeves - 18-9-2011 at 12:17

there was a video on youtube for a while that got took down of a guy heating potassium carbonate or hydroxide,i forget which, with potassium ferrocyanide in a test tube. potassium cyanide formed like a beach around the mixture. it was in german so i had to use google translater on his notes. he didnt say how he kept away from the hcn gas though.careful.
oh! and the test tube was tilted just above horizontal while heating.
[Edited on 18-9-2011 by cyanureeves]

[Edited on 18-9-2011 by cyanureeves]

mr.crow - 20-9-2011 at 06:35

Speaking of Germans, here is a thread. Translation

Don't die

Melgar - 25-9-2011 at 12:32

Oh, hey, that was my thread. :) I know KOH can corrode glass, but my point was that you can do the KOH/urea reaction in glass without noticeably damaging it, probably because once molten, the reaction proceeds rather quickly.

For making NaCN, it would probably be best to heat a stochiometric mixture of sodium carbonate/hydroxide, urea, and charcoal to red hot, probably in a good-sized charcoal fire. This reaction does give off lots of ammonia, which will react with red-hot charcoal to form hydrogen cyanide, so watch out for that.

Oh, and you know what makes an excellent crucible? Empty disposable propane tanks with the top sawed off. They're clean, thick enough to stand up to high temperatures, and most of us probably have a few laying around already. Of course, you do need to make DAMN sure, they're actually empty before actually sawing the top off one.

AndersHoveland - 26-9-2011 at 07:13

Often times you can find good tutorials for making cyanide on suicide forums. I found an interesting method of making hydrogen sulfide this way.

testimento - 5-7-2013 at 19:33

For this topic, I would like to continue.

Could NaCN be produced by following method:

-Burn calcium carbonate into calcium oxide at 1000C
-Mix 3 moles of urea and 1 moles of calcium oxide at urea melting, when calcium cyanate is formed
-Calcinate calcium cyanate at 700-900C protected from oxygen to produce Calcium Cyanamide
-Mix 1 mole of calcium cyanamide, 1 mole of sodium carbonate and 2 moles of carbon at 900C temperature, where carbonate will melt and reaction will produce molten sodium cyanide, carbon monoxide and calcium oxide and the sodium cyanide could be poured out in molten stage in ceramic container where it can be cooled and smashed into powder and put into proper container.

Sources:

https://en.wikipedia.org/wiki/Calcium_cyanamide
http://www.sciencemadness.org/whisper/viewthread.php?tid=142...

If this process works, it looks the most straightforward and OTC to me, apart from the trouble of making the furnace. I suggest using clay flowerpot or SS cooking pot with clay coating and 0.5mm nichrome wire installed inside clay surface with dimmer(triac) to get over 1000C tempes. The pot could be insulated with quite thick layer of clay, cement or other stuff too.


Another process is to blow ammonia through glowing coal, but IDK about this process a lot, sounds like PITA to get HCN out from CO2, CO and soot created by the coal, and the heating of it would be another PITA, maybe a shitload of nichrome around quartz tube, but can you get it glowing without reacting air with it too?

[Edited on 6-7-2013 by testimento]

AJKOER - 7-7-2013 at 17:02

OK, a possibly cheap and relatively easy path to a cyanide that I have been considering. Take safety precautions as this preparation can still accidentally lead to exposure to deadly gases including both CO and HCN.

1. A possible source of HCN is by burning a nitrogen containing plastic as per Wikipedia (http://en.wikipedia.org/wiki/Hydrogen_cyanide ):

"and in smoke from burning nitrogen-containing plastics"

An important point is precisely which plastic, however, as a low nitrogen content is not desirable. This source (http://answers.yahoo.com/question/index?qid=20101104220951AA... ) may provide an answer as it states:

"HCN forms when synthetic fibers containing Orlon® or Acrilan® burn. Acrilan® has an empirical formula of \rm CH_2CHCN, so HCN is 50.9% of the formula by mass. A rug in the laboratory measures 12.0 times 15.0 ft and contains 30.0 oz of Acrilan® fibers per square yard of carpet. If the rug burns, what mass of HCN will be generated in the room? Assume that the yield of HCN from the fibers is 20.0% and that the carpet is 36.0 % consumed"

Acrilan is a brand name for acrylic fiber which contains essentially Acrylonitrile (formula C3H3N, see discussion at http://en.wikipedia.org/wiki/Acrylonitrile).

I have long known that a fire in a building having plastic rugs, curtains,...can produce HCN, which is perhaps equally dangerous as is the CO and the fire itself.

2. Direct the smoke using an air flow into a scrubbing solution of iced NH4OH (other choices include NaOH, KOH, but NH4OH also does dissolve CO).

That's it. The scrubbing solution will contain NH4CN (see http://en.wikipedia.org/wiki/Ammonium_cyanide for more details) along with some nitrite and nitrate along with some exit gas of toxic CO. I have chosen this unstable cyanide as it decomposes readily (permitting cyanide separation) as follows, per Wikipedia:

"Ammonium cyanide decomposes to ammonia and hydrogen cyanide, often forming a black polymer of hydrogen cyanide:

NH4CN → NH3 + HCN "

and I speculate that adding some H2O2, CO2 and Cu (or no Copper as with Hydrogen peroxide the safer cyanate (CNO-) could be formed from the cyanides if pH 9-10, see http://www.h2o2.com/industrial/applications.aspx?pid=106&... ) to the aqueous cyanide/nitrite/nitrate mix would, in time, release N2, NO (see my comments at http://www.sciencemadness.org/talk/viewthread.php?tid=6381#p... ), previously dissolved CO and possible HCN. The latter could be re-absorbed leaving only a solution of HCN and some CuCN/Cu(CN)2.

[EDIT] I would consider adding a secondary scrubbing solution of fine Fe in a suspension of ammonia water to address excess CO. In all cases, this preparation should be performed in a fume hood or outdoors.


[Edited on 8-7-2013 by AJKOER]

Clan-destined - 5-1-2019 at 21:31

Can you ppl please dispense with this urea talk for preparation of sodium cyanide? This shit is a no-brainer:
1. Sodium hydroxide
2. Equal amounts of potassium ferrocyanide (yes, you may use sodium ferrocyanide--geez... Using potassium ferrocyanide gives the identical potassium cyanide. In fact, it's been said that the only difference between the two molecules is that one bottle has a label that reads "potassium" before the cyanide and the other reads a "sodium" before the cyanide.).
3. A clean metal vessel (tablespoon; lid to a jar of spaghetti sauce, etc).
4. Propane and a match.

Now mix the ferrocyanide in with the hydroxide. Apply lots of heat. Don't worry about cyanide poisoning; your propane burns off the evolving hydrogen cyanide gas. But to satisfy the weenies on this board, I declare a warning: DON'T TRY THIS WITHOUT A FUME HOOD OR RISK CERTAIN DEATH BY INHALING EVEN A BIT OF THE GAS THAT EVOLVES! IT'S BEEN SAID THAT EVEN A CUBIC CENTIMETER OF THIS STUFF IS FATAL! Ok, the weenies are now happy...
As you continue to heat, the mixture turns from a faint yellow, coarse powder to a black bubbling viscous liquid. The flames you see shooting out is your hydrogen cyanide gas. You can't keep heating it much beyond this or risk losing all the cyanide part of your sodium cyanide! Total heat time can't run for over 5 minutes for a small cook. You're done when the sodium cyanide begins to precipitate out as a white liquid that floats on top. Turn off the heat, you're done!
Let this substance cool into a hard, crusty material.

The ferro in ferrocyanide precipitated out of the reaction, and it's now time for you to separate it from the goods. Simply dissolve the moonrock in a small quantity of warm water (the purpose of which is to dissolve your sodium cyanide, while leaving all other ingredients behind). Decant the rust from the sodium cyanide solution.

You may now remove the water from your sodíum cyanide using any means available. The white, crystalline crusty stuff left is crude sodium cyanide. Proof: drop a small chunk in some HCL. Prussian blue? Check! The stench of hydrogen cyanide immediately filling the garage? Check!
Do we have our sodium cyanide? Check...

Mabus - 20-1-2019 at 08:20

Unfortunately neither ferro nor ferricyanides are not something you can just find at the local store, while urea and KOH is something you do. Also, both urea and alkali hydroxides are much cheaper, so there's also the cost to be considered.

S.C. Wack - 20-1-2019 at 10:30

The urea method does not use hydroxides esp. KOH w/10% water. It requires the most anhydrous carbonate you got. Same with the ferrocyanide.

Mabus - 20-1-2019 at 12:30

Quote: Originally posted by S.C. Wack  
The urea method does not use hydroxides esp. KOH w/10% water. It requires the most anhydrous carbonate you got. Same with the ferrocyanide.

True, both work and both are very OTC. I too would definitely want some ferro or ferricyanide, since there are fewer side products. But alas, gotta do what I can with what I got.

AJKOER - 20-1-2019 at 16:20

In my opinion, an interesting path to CN- from OCN- based on some radical chemistry, which I argue is the basis for a famous patent, see Clancy Patent discussion at http://www.sciencemadness.org/talk/viewthread.php?tid=87030#... .

Or, disregard my theoretical discussion and lookup details on execution of the patent, which employs an electrolysis approach.

[Edited on 21-1-2019 by AJKOER]

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

Quote: Originally posted by Mabus  
I too would definitely want some ferro or ferricyanide, since there are fewer side products.


Inorg Syn says if done right the potassium cyanate is nearly pure in high yield and the Na salt is easily purified...btw with carbonate and ferrocyanide the extra mol of cyanide product comes with one of cyanate. It might be wiser to add nothing at all to the ferrocyanide and lose N2 than to heat it with NaOH.

PirateDocBrown - 11-2-2019 at 08:46

Fe7(CN)18 + H3PO4 = FePO4 + HCN

That's laundry bluing, you can get it at Wal-Mart. Dry it, first.

Condense the HCN with a very cold condenser fluid, or you'll lose a lot to evap. Catch the condensate in chilled EtOH, the solution is much easier to handle, Pure prussic acid boils around RT.

Make damn sure you have good ventilation, duh.

You want Na or K CN, dissolve the base in the EtOH first. Even easier.


[Edited on 2/11/19 by PirateDocBrown]

Fantasma4500 - 21-10-2021 at 04:33

2. The process of Claim l wherein a) step for mixing of raw materials is characterized in that 2.5~2.8:i mol ratio of urea and sodium carbonate are charged the blender, and 200 mesh-sized iron powder and 200 mesh-sized anthracite coal powder mixed by 1:1 weight ratio are added by the quantity corresponding to 0.2-0.4 % of raw material, and then raw materials and additives are uniformly mixed.

3. The process of Claim 1 wherein b) step for first-order reaction is characterized in that the mixture of claim 2 is charged a reactor with and then the temperature of the reactor inside is hold at 300-350 °C for 2 hours to make the reactants of the mixture react.

4. The process of Claim 1 wherein c) step for second-order reaction is characterized in that the temperature of the reactor inside is hold at 650-750 °C for 1 hour to make the first-order reaction product deoxidized.
https://patents.google.com/patent/WO2016199944A1/en

i suppose butane could be pumped into reaction vessel to keep oxygen out, its very heavy.

also RIP anders

macckone - 21-10-2021 at 13:52

So that patent appears to be making sodium cyanurate then heating with iron and carbon to catalyze to sodium cyanide.

walruslover69 - 21-10-2021 at 17:35

I have carried out a similar procedure by nurdrage with success a long time ago. Carbon does the reducing. what is the role of iron? is it a catalyst? what would that mechanism be?

Fantasma4500 - 22-10-2021 at 03:52

i just realize, as with NaNO3 to NaNO2, iron oxalate can be used as it thermally decomposes at relatively low temperature, forming superfine iron powder
this would keep oxygen out and at the same time reduce

macckone - 22-10-2021 at 07:08

walruslover69,
the carbon and iron appear to be strictly catalytic as they are only a few percent of the other reactants.
I believe they are using the urea itself as a reductant. It is added in a good molar excess.

walruslover69 - 22-10-2021 at 07:59

I didn't see that It was only a catalytic amount of iron and carbon. Makes sense that the iron would be an oxygen scavenger. I don't think urea is the reductant though, Is it truly just a thermal decomposition then?

The first heating step with urea and sodium carbonate at 350 forms sodium cyanate. The urea decomposes, and it's quite clear when the reaction is over and stops giving off large amounts of ammonia.

The second step is the conversion of cyanate to cyanide. I've read through several papers and threads and I'm still confused about the actual process going on. I always assumed it was a reduction of NaCNO + C ----> NaCN + CO or 2NaCNO + C ----> 2NaCN CO2. But if the reaction takes place without a direct reduction that would mean that NaCN is the more thermodynamically stable compound and only a catalyst is needed.

doing first order calculations from wiki's thermo data

NaCNO enthalpy formation = -400kj/mol
entropy = 119.2 j/mol

NaCN enthalpy formation = -91kj/mol
entropy= 115.7 j/mol

O2 entropy = 205,14 j/mol

For the reaction 2NaCNO --> 2NaCN + O2
Gibbs free energy = 560 kj/mol at 25C and 425 kj/mol at 700C.

these values are for room temp, so one problem might be that the thermo data is significantly different in the molten phase, but I couldn't find data for that. There is the kinetic factor of O2 constantly evolving into open air that would shift the equilibrium to cyanide, but I would be skeptical that it would be enough to could overcome the 425 kj/mol at any significant rate.

Am I missing something ?

macckone - 22-10-2021 at 08:33

walruslover69,

There is excess urea, it will form biuret and cyanuric acid giving off ammonia. But there is not enough sodium carbonate for it to react with so it is going to act as a reducing agent at the higher temperature. The ratio is 2.8 moles of urea to 1 mole of sodium carbonate. That means there is 0.8 moles excess to act as a reducing agent. With the iron and carbon catalyst, that may be sufficient.

walruslover69 - 22-10-2021 at 14:59

The urea will just thermally decompose. I believe it starts around 100C There is no way it would be stable at 350C for 2 hours.