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Hawkguy
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Its probably easiest (If you're looking for convenience) to add cooled Hydrochloric Acid to Potassium Ferricyanide, and distill the Hydrogen Cyanide
directly into aqueous Potassium Hydroxide.... I guess this only really works in places with OTC Potassium Ferricyanide like Canada...
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careysub
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Quote: Originally posted by Hawkguy  | | Its probably easiest (If you're looking for convenience) to add cooled Hydrochloric Acid to Potassium Ferricyanide, and distill the Hydrogen Cyanide
directly into aqueous Potassium Hydroxide.... . |
That is what I would have tried.
But Dan posted that this does not work very well due to polymerization as the HCN condenses into the base.
I am hoping he clarifies whether he uses acid to stabilize the product while being collected, or afterwards, which may help to explain the the
difference between the two apparently similar scenarios he described.
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Dan Vizine
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| Quote: Originally posted by careysub | | Quote: Originally posted by Hawkguy | | Its probably easiest (If you're looking for convenience) to add cooled Hydrochloric Acid to Potassium Ferricyanide, and distill the Hydrogen Cyanide
directly into aqueous Potassium Hydroxide.... . |
That is what I would have tried.
But Dan posted that this does not work very well due to polymerization as the HCN condenses into the base.
I am hoping he clarifies whether he uses acid to stabilize the product while being collected, or afterwards, which may help to explain the the
difference between the two apparently similar scenarios he described. |
I answered this on p.24. I use H2SO4 to stabilize any HCN which is collected as such (now that I fully appreciate the danger).
There is polymerization going on, I'm just not sure it's the HCN itself that causes it because it only happens...well, let me summarize:
1) HCN is generated, condensed in a distillation head, then allowed to drip into cold, stirred aq. NaOH directly. Result: Black solution.
2) HCN is generated, condensed in a distillation head, collected in a flask containing H2SO4 stabilizer. This liquid is then allowed to drip into
cold, stirred aq. NaOH. Result: Colorless to slightly yellow solution.
3) HCN is generated, condensed in a distillation head, collected in a flask with no stabilizer. This liquid is then allowed to drip into cold, stirred
aq. NaOH. Result: Colorless to slightly yellow solution. It IS NOT suggested that you try this, I did it only out of ignorance.
Interesting observation: The material in the discharge end of the distillation head (which hasn't touched base yet) also turns black in the "direct
addition to base" scenario described in (1). It doesn't do it in (2) or (3).
I know this sounds crazy. But I have done it several times (both ways) with the same results always. The collected HCN was typically (but not always)
stored overnight in a freezer before addition to base.
A note about stabilization: This is done to prevent explosion (uncontrolled polymerization) of HCN which is catalyzed, especially strongly, by the CN
anion. It is said that glassware needs to be very clean before condensing liquid HCN into it. Since many labs use base bathes to clean glassware, it
should be rinsed off very thoroughly. Stabilization with 1 - 2 % H2SO4 can be seen to be very appropriate to staying safe.
[Edited on 22-10-2014 by Dan Vizine]
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careysub
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| Quote: Originally posted by Dan Vizine | ...
I am hoping he clarifies whether he uses acid to stabilize the product while being collected, or afterwards, which may help to explain the the
difference between the two apparently similar scenarios he described.[/rquote]
I answered this on p.24. I use H2SO4 to stabilize any HCN which is collected as such (now that I fully appreciate the danger).
There is polymerization going on, I'm just not sure it's the HCN itself that causes it because it only happens...well, let me summarize:
1) HCN is generated, condensed in a distillation head, then allowed to drip into cold, stirred aq. NaOH directly. Result: Black solution.
2) HCN is generated, condensed in a distillation head, collected in a flask containing H2SO4 stabilizer. This liquid is then allowed to drip into
cold, stirred aq. NaOH. Result: Colorless to slightly yellow solution.
3) HCN is generated, condensed in a distillation head, collected in a flask with no stabilizer. This liquid is then allowed to drip into cold, stirred
aq. NaOH. Result: Colorless to slightly yellow solution. It IS NOT suggested that you try this, I did it only out of ignorance.
Interesting observation: The material in the discharge end of the distillation head (which hasn't touched base yet) also turns black in the "direct
addition to base" scenario described in (1). It doesn't do it in (2) or (3).
I know this sounds crazy. But I have done it several times (both ways) with the same results always. The collected HCN was typically (but not always)
stored overnight in a freezer before addition to base.
...
[Edited on 22-10-2014 by Dan Vizine] |
Having the case by case comparisons is very helpful in pondering what may be going on here.
The difference between 1 and 3 is what is puzzling - no polymerization with the acidic stabilizer (2) is what we would expect.
A few useful facts there - the pH of HCN itself is about 4.5, but to prevent polymerization the pH should be 4 or below.
Polymerization is autocatalytic so unnoticeable amounts of polymer, once formed, can drive polymerization.
Initiation of polymerization of HCN during distillation is a known problem, there are patents that seek to address this.
The blackening of the discharge end in 1) suggests that perhaps the dripping process itself is causing the transport of base up to the distillation
tube end. Perhaps microdroplets are being created that then contaminate the tube end with hydroxide? This then sets a troublesome degree of
polymerization in motion.
But why would this not also happen in 3) when not adding an acid-stabilized product? Perhaps the freshly distilled material (recently warm) is more
"active" in some way and more sensitive to trace quantities of base? Dissolved traces of newly formed HCNx that settle on surfaces later? Effects of
trace oxidation of the HCN?
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Dan Vizine
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Yeah, it's a difficult nut to crack. So many maybe's...
About the blackening in the condenser in (1)...the idea of splashes is very unlikely. The drip tube of the 14/35 distillation head was fitted with a
Teflon tube about a foot long and 1/8 "dia. to lead the liquid HCN into the base flask.
The HCN is never allowed to warm above 0 C except for the brief residence time in the dropping funnel. Even then, it doesn't warm very high at all
since it starts out colder than 0 C and is poured into a pre-chilled dropping funnel.
I'm one of the sub-group that easily smells HCN. Suitably diluted, I really like the smell...delicious almond pastries!
As poisons go, I prefer working with this type. If you walk away at the end of the day, it's behind you. Not like working with MeI or Me2SO4, where
you can only hope you didn't just methylate any of your essential DNA. I even prefer working with HCN over HMPA.
Funny story, a former boss worked at DuPont in Niagara Falls. During an ill-advised pipeting incident (it was a different time....you know) he got a
mouth full of LHCN. I asked him what he did...his answer...I spit it out. Probably with a lot of mouth rinsing.
The most interesting HCN experience I've ever had was maybe 25 years ago when I opened an autoclave in which a Ba salt of some arcane mercapto
S,N-heterocycle was being reacted. Apparently the reaction could produce HCN as a side-product. This wasn't mentioned in the patent I was following (I
know..big surprise) and I got a pretty good whiff. I had that little rush up the spine you get when you realize something bad just happened but it
hasn't hit yet. Then it hit and I got tunnel vision. It was getting a bit dark in the room and I turned to walk toward a labmate and was preparing to
say "cyanide". Before another 2 steps the lights were coming on, and just about as quickly as it hit, it was subsiding.
[Edited on 23-10-2014 by Dan Vizine]
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Dan Vizine
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I wonder what possible role that the other tautomer, hydrogen isocyanide, may play (if any)? It is supposed to quite base stable, so maybe no role at
all.
It's clear that either HCH or HNC are both able to produce polymers that are black.
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Hawkguy
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I apologise if this sounds stupid, but what about reacting the Potassium Ferricyanide and Hydrochloric Acid stoichiometrically, then adding aqueous
Potassium Hydroxide and recrystallizing? I wouldn't happen to know of a suitable solvent unfortunately, but hopefully the idea comes across.
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careysub
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| Quote: Originally posted by Dan Vizine | ...
The most interesting HCN experience I've ever had was maybe 25 years ago when I opened an autoclave in which a Ba salt of some arcane mercapto
S,N-heterocycle was being reacted. Apparently the reaction could produce HCN as a side-product. This wasn't mentioned in the patent I was following (I
know..big surprise) and I got a pretty good whiff. I had that little rush up the spine you get when you realize something bad just happened but it
hasn't hit yet. Then it hit and I got tunnel vision. It was getting a bit dark in the room and I turned to walk toward a labmate and was preparing to
say "cyanide". Before another 2 steps the lights were coming on, and just about as quickly as it hit, it was subsiding. |
That is so scary.
It is a good thing that not only is cyanide detoxified by the body, but that cytochrome oxidase complex inhibition is highly reversible.
You got enough in one breath so that the initial CN surge substantially inhibited brain cytochrome oxidase, causing the visual blackout (which can
simulate by holding your breath long enough), but with CN-free blood circulating immediately afterward the CN released from the co, reactivating it.
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careysub
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| Quote: Originally posted by Hawkguy | | I apologise if this sounds stupid, but what about reacting the Potassium Ferricyanide and Hydrochloric Acid stoichiometrically, then adding aqueous
Potassium Hydroxide and recrystallizing? I wouldn't happen to know of a suitable solvent unfortunately, but hopefully the idea comes across.
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You would at least end up with a mixture of FeCl3 and KCl with your KCN, not a desirable product mixture I expect.
After forming aqueous HCN perhaps you could extract it into ether, then extract the ether-HCN solution with aqueous NaOH or KOH.
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Dan Vizine
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The deep blue ferric ferricyanide which results from the acid reaction (not all of the CN comes off the iron) is very bulky. I believe that this is
called Prussian Blue. It would be an isolation nightmare. Catalysis by Cu salts and/or Cu helps push the reaction further according to one source.
Anyway, a way around the problem has been found. I have just always wondered why it happens, though.
[Edited on 24-10-2014 by Dan Vizine]
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Dan Vizine
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| Quote: Originally posted by careysub | | Quote: Originally posted by Dan Vizine | ...
The most interesting HCN experience I've ever had was maybe 25 years ago when I opened an autoclave in which a Ba salt of some arcane mercapto
S,N-heterocycle was being reacted. Apparently the reaction could produce HCN as a side-product. This wasn't mentioned in the patent I was following (I
know..big surprise) and I got a pretty good whiff. I had that little rush up the spine you get when you realize something bad just happened but it
hasn't hit yet. Then it hit and I got tunnel vision. It was getting a bit dark in the room and I turned to walk toward a labmate and was preparing to
say "cyanide". Before another 2 steps the lights were coming on, and just about as quickly as it hit, it was subsiding. |
That is so scary.
.... |
The really scary part is if you've ever seen a cyanide antidote kit. It relies on totally untrained people to get large needles into your veins
quickly. Good luck.
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careysub
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| Quote: Originally posted by Dan Vizine | | The deep blue ferric ferricyanide which results from the acid reaction (not all of the CN comes off the iron) is very bulky. I believe that this is
called Prussian Blue. |
Making Prussian Blue was my favorite "chemical magic" reaction with my ChemCraft chemistry set.
It has the distinction of being the wholly first synthetic dye ever.
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Dan Vizine
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Oh, back in good old days when chemistry sets actually contained chemicals!
My first chemistry set, back in the early 60's, set the course of my life. That can't happen today unless the child has very low standards. Growing
crystals, investigate pH....just kill me now. I preferred to set fire to steel wool in an atmosphere of Cl2 just as "The Golden Book of Chemistry
Experiments"showed me how to do.
[Edited on 25-10-2014 by Dan Vizine]
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careysub
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Have you ever used HCN in the Gatterman synthesis?
I have done some looking for a procedure description. Gatterman's two texts on-line here don't have it, and I haven't found any elsewhere despite
substantial Googling.
Accounts mentioning Gatterman do so only in passing (describing some other aldehyde production procedure) or describe an 'improved' version (most
often with zinc cyanide).
In a world where alkali cyanide salts are essentially unavailable the supposed superior safety of zinc cyanide is illusory - obtaining it requires
making HCN anyway.
And oddly, there is apparently no such taboo about using dimethyl sulfate. OrgSyn.org has DMS procedures, but no HCN. Shulgin declines to give an HCN
procedure (which gives much better results than the one he does describe), but has no problem with describing a procedure using 126 g of DMS.
[Dimethyl sulfate was actually used as a war gas in WWI - it is similar to mustard gas, but is 1/5 as potent - would you do a synthesis calling for 25
g of mustard gas instead?]
I would much rather run a reaction with HCN than DMS. If you check the NIOSH safety limits for the two compounds, DMS has a much lower permissible
level (this is good rule-of-thumb way of estimating low level exposure hazards). HCN skin exposure risks are zero, but are severe with DMS. HCN has no
cumulative or delayed effects - not so DMS. HCN has a useful warning odor, again nada DMS. I could go on.
[Edited on 27-10-2014 by careysub]
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Dan Vizine
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No, I've never done the reaction. We probably would have been much more likely to go the BuLi followed by DMF route. The place where I spent nearly my
whole synthesis career wasn't the type of place that would've had a convenient source of HCN available, but we had gallons of butyl lithium.
Personally, I couldn't agree with you more. I'm not very impressed by the dangers of the chemicals that get you in the here and now. I've never found
that the available safety options for using these things made me feel unsafe. They seemed adequate or at least it was a chance I was willing to take.
Over the course of a career spanning decades, it's not too uncommon to realize that the difference between you and dead you is about an eighth of an
inch of glass. I'm sorry, but sometimes it was just convenient to do reactions with potassium cyanide in DMF or potassium fluoride in DMSO at the 22 L
scale. It doesn't take much imagination to realize that a splash with the fluoride isn't something you'd come back from. Common sense precautions were
always enough. I never witnessed or experienced a life-threatening situation.
The scary things were exactly the types of things you mentioned. The scariest things were the reactions that had HCl and a potential formaldehyde
source like an N-hydroxymethyl group together in one pot. You can leave work that day smiling like a fool, and then 20 or 30 years later the molecular
machinery goes awry.
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careysub
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| Quote: Originally posted by careysub | ...
The detoxification rate is about 0.07 mg per minute per kilogram of body weight. if you weight 70 kg you can absorb 5 mg a minute continuously without
suffering any ill effect (don't test this - it is a safety feature, not a challenge). The 25 mg LD given above requires breathing a high vapor
concentration so that the entire dose is absorbed in a minute or less (e.g. 2.5 grams evaporated in a cubic meter of air). |
I apparently cannot edit my original post about safety/hazard data. The source I pulled up for the detoxification rate had a misprint, the rate is
actually 0.017 mg/min/kg NOT 0.07 mg/min/kg, so it is 1/4 as fast. This means you only metabolize 1.25 mg/min.
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Oxirane
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What happened to the classic carbothermic reduction that contains maybe three of the most available chemicals there are?
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careysub
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| Quote: Originally posted by Oxirane |
What happened to the classic carbothermic reduction that contains maybe three of the most available chemicals there are? |
And if that is what you have to do to get KCN then "unavailable" it is!
There is a significant difference between being able to buy KCN, and needing to first buy an electric (or other) furnace so that potassium
ferricyanide, carbon, and potassium carbonate can be heated at 650 C for three hours first, then extracted and purified to get the same KCN. (Also it
vents carbon monoxide from the crucible, much less dangerous than HCN, but not harmless).
This is a method to redress unavailability, it does not change the fact that you cannot buy it.
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Dan Vizine
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The carbothermic process is one of those industrial processes that doesn't translate well to the home. I welded a steel crucible, built a forced-air
coal furnace, tried the reaction several times, I even had a spin evaporator to quickly evaporate the ultimate product and still the best I got was a
cyanide odor. The performance of the reaction is very subjective, the amount the crucible can be open to the air needs to be just right (with no
criteria for "correct" except, apparently, success or failure at the end), it's a reproducibility nightmare. There's a lot of luck involved.
I guess some members have gotten it to work, I haven't pursued it. But, if you can get potassium ferricyanide and H2SO4 you'd be crazy to go the other
route.
edit: I noticed people mentioned using HCL. This is a poor idea. You need to heat the mixture to get the HCN out. You don't want HCl carry over. H2SO4
is the answer.
[Edited on 28-10-2014 by Dan Vizine]
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Oxirane
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Versuchschemie presented a method that uses urea, charcoal and sodium carbonate to first generate sodium cyanate and then reduce it to cyanide. I have
performed this test and although I did not have test to determine if it was cyanide or cyanate, it corroded aluminium and the synthesis gave all clear
indicators same as the VC describes.
I think this is viable method to make even kilos of cyanide salts when needed, because electric furnace is quite easy to make once you get the specs
and materials, since you will need only some nichrome and a dimmer to control the power. I made quite a few different designs before I got it all
right but then I had a furnace that could bring anything that fits inside to 1000C. This oven is not to be run inside your living room for sure so
it's not otc for people living in cities but for just about everyone else, if the syntesis works as it stands, even a little bit too easy method to
make large amounts of it.
[Edited on 28-10-2014 by Oxirane]
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Dan Vizine
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Yes, mine also gave the "indicators" and I also used the urea method, but the product wasn't cyanide.
Corroding aluminum is fairly meaningless as an indicator of having isolated a salt of HCN, IMHO. After all, if you decompose the cyanide to NaOH
during isolation you'll also see the same thing.
I'll believe in this method as a viable home prep. when somebody either does a further reaction with it [the product] and gets the expected product in
the expected yield, or they perform a chemical assay. After extensive testing over many, many runs and careful analyses of the various products, you
just may hit upon it. Or maybe not.
There isn't any question about the ferricyanide and acid product.
[Edited on 28-10-2014 by Dan Vizine]
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Oxirane
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So in where do it goes wrong? I understand that many have performed this synthesis succesfully. I still have got what's left on that synthesis in a
vial, so I can test it out if you give me a method for it.
I also note that NaOCN reduction is very temperature sensitive. I made a test with insulated propane burner with calcium carbonate and I never got any
basicity with litmus paper, while my electric furnace did that easily. The flames from supposedly carbon monoxide were generated at the high end of
heating and the whole furnace interior glowed bright cherry red. The clunker left in the stainless steel crucible was broken down with chisel and
hammer and dissolved easily into hot water, filtered and precipitated with ethanol.
The aluminium was wrapped around the SS container that held the clunker for the time for it to cool down. It stood there overnight and aluminium was
eaten away. It was never in direct contact but there was about 100mm minimum distance from the clunker to the foil. So gases evolved from the clunker
released something that had disastrous effect on the foil. It was just simply gone, like vaporized.
[Edited on 28-10-2014 by Oxirane]
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Dan Vizine
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http://www.cyanidecode.org/cyanide-facts/sample-analysis
Pick your poison, no pun intended.
OR...
Put some in a test tube, outdoors. Add a little sulfuric acid and warm the bottom while you cool the upper part with a wet, cool paper towel. Do you
see a band of condensation (liquid HCN)?
"All Your Children Are Poor Unfortunate Victims of Lies You Believe, a Plague Upon Your Ignorance that Keeps the Youth from the Truth They
Deserve"...F. Zappa
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Oxirane
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I'm ashamed to admit, but after all the other equipment I possess, I do not have test tubes! 
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Hawkguy
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I think someone might have already mentioned this because I haven't read through all the pages, but its worth noting that apparently Sodium Cyanide is
(harder?) to store than its Potassium Counterpart as it hydrolyses more easily. Ive only seen this from one source, but its worth something I guess.
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