evil_lurker
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Distilling HCN from potassium ferrocyanide...
I've decided to go all out in my quest for KCN/NaCN so I can do some research with platinum group metals. This is a project I've had in the works for
more than a year. Its taken quite a bit of planning and many thousands of rounds of the little hamster wheel in my head.
Unfortunately NOONE will sell me this compound, period.
So if I want it, I'm going to have to make it myself. Unfortunately its not the easiest thing to do in the world. I think the best route is going to
be to add diluted H2SO4 to potassium ferrocyanide using the method found in brauer's inorganic chemistry.
Since I do not need neat HCN, the plan is to condense the HCN gas immediately into an alcoholic solution of potassium hydroxide, take the insoluble
KCN out, vacuum filter, and then place in a vacuum dessicator over CaCl which should hopefully form the addition product with the alcohol and dry it
out so I can get an accurate weight reading.
I believe I have come up with an apparatus that only has 4 ground joints, none of which are horizontal. Plus there is no addition funnel on the
generation flask. The generation flask is goign to be a 24/40 2L RB flask w/threaded thermometer port and heated heated with a mantle.
I found an interesting inlet adapter made by chemglass that allows fluids to be added via a luer lock and syringe:
The idea is pretty simple, chill the flask pre-charged potassium ferrocyanide along with the sulfuric acid, then shoot it in while its still cold
using a luer tubing extension adapter, then turn on heat, light fuse and get away till its done its thing. Then again, it might be better to heat the
contents of the flask over the boiling point of HCN using a water bath and see just how fast it reacts. I'm a bit leery of using a funnel simply
because it would involve another joint which could leak and would be one more thing to clean.
The reciever flask will be simple as well... a 2L flask filled with an equimolar amount of amount of KOH in MeOH based upon the potential HCN, with an
inlet adapter and 400mm double coil condenser running ice water, vented with an inlet adapter off into a garden hose running downwind.
It should be that 100% of the HCN should be liberated at 70ºC... but I plan on taking no chances in that department and some sort of neutralizing
compound will be injected into the luer port.
For safety, I plan on taking no chances in that department either. Since I don't have a hood, I wil have to do things outside with a respirator.
Luckily, I recently managed to get my hands on a real industrial SCBA and tyvek hazmat suit. The SCBA is made by MSA, apparantly new old stock, and
has a quick refill connection kit so it can be refilled from a larger stationary high pressure air tank several times without ever switching tanks or
removing the pack. This feature was created by MSA so that firefighters could quickly refill their tanks. In fact I could probably just leave it
hooked to the big tank while I work, and should I need to leave the area for whatever reason just unhook.
Thoughts?
And yes, I know I'm crazy.
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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PainKilla
Hazard to Others
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I don't think that HCN is that bad if you make sure all your connections are OK, and you do it outside, in an isolated region, not making huge
amounts.
That said, making it inside without a hood is crazy but hopefully no one ever attempts this.
This journal may be of use:
Attachment: Potassium Ferrocyanide Decomposition Using Sulfuric Acid - HCN generation.pdf (286kB)
This file has been downloaded 6287 times
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not_important
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You could go the lower yield route of heating a ferrocyanide to dull redness, or ferrocyanide and carbonate, or those two plus carbon. Extraction with
water, followed by precipitation using alcohol.
For your design, consider putting suction on the vent, drawing the gases through a wash bottle containing bleach .
[Edited on 27-11-2007 by not_important]
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Magpie
lab constructor
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How much KCN do you need/want lurker?
This outfit offers it (along with some other interesting albeit expensive chems.) There is a serious caveat, however: it has to be picked up in
person, i.e., no mailing. 
http://www.hms-beagle.com/
This is the only place I've seen KCN offered to individuals.
[Edited on by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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JohnWW
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KCN, besides being a preparative reagent, is also an analytical reagent. I have worked in water quality laboratories in New Zealand which had it for
water analysis purposes. I think one of the analyses it was used for was a colorimetric/spectrophotometric method for Fe as Fe(III), based on the
intense red color of potassium ferricyanide.
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MagicJigPipe
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Why would law enforcement consider KCN to be a drug precursor? Is there an illegal drug that I'm not aware of that in which is synthesis depends on
KCN more so than other commen reagents?
Because of benzyl cyanide?
*Sigh*... Fleaker, the sight that sells KCN. Go to the KCN section and read it. Big bold letters. Can't miss it.
Don't get so pissed over nothing.
**Tried to put a link but I can't get it to work. I'm sure you can figure it out though.**
Am I setting a new record for edits or what?
[Edited on 28-11-2007 by MagicJigPipe]
[Edited on 28-11-2007 by MagicJigPipe]
[Edited on 28-11-2007 by MagicJigPipe]
[Edited on 28-11-2007 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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JohnWW
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It is used in organic chemistry for adding an additional C atom to a chain of C atoms, by means of nucleophilic attack by CN- to form a
nitrile/cyanide, followed by hydrolysis. This is by SN2 reaction, on an organic halide, displacing the halide as an anion, with the resulting nitrile
able to be either acid or base-hydrolysed to a caboxylic acid; or similarly on aldehydes and ketones to form cyanohydrins, which can then form by acid
hydrolysis alpha-hydroxy-carboxylic acids and then alpha-alkenyl-carboxylic acids by dehydration.
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garage chemist
chemical wizard
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PainKilla, that article was extremely helpful. Now I know that very high yields of HCN are possible with ferrocyanide and dilute H2SO4.
The correct concentration of the H2SO4 is the key to success.
If you just want a few grams or tens of grams of KCN for experiments and small-scale preparations, the melting process would be the best method since
no gaseous HCN is required.
Dehydrate potassium ferrocyanide at 105°C in the oven and heat the salt to red incandescence in an iron or steel crucible under rigorous exclusion of
oxygen.
It decomposes into KCN, Fe, C and N2, KCN is the only soluble component of the fused residue so an extraction directly gives you the KCN.
One would ideally use methanol for this extraction since the solubility of KCN is not so ridiculously high in it than in water.
A soxhlet would be ideally suited to the extraction.
Out of curiosity, why do you need KCN for work with platinum group metals? I've done my fair share of reactions with Pt and Pd and never required any
cyanide. Same with silver and gold.
What are the compounds you want to make?
[Edited on 29-11-2007 by garage chemist]
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MagicJigPipe
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Yes, I realize this, but surely they have something in mind when they say that law enforcement may consider it a drug precursor. Fleaker, read my
last post on this thread. I edited it.
Damnit, now I'm paranoid about purchasing cyanides.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Fleaker
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Forget I said anything about it.
I think garagechemist's idea is best. A steel container of suitable size could easily be made and it could be kept in a charcoal bed if one
controlled the draft. MeOH would work nicely as well.
I don't know what type of plating you're doing garage chemist, but if you do any decent gold plating, then the potassium gold cyanide salt is very
useful. Agreed that cyanide doesn't do much for PGMs though...
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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evil_lurker
National Hazard
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High temp routes to HCN have been effectively ruled out... for now anyways since I don't have enough money to plunk down on some platinum gauze to
load in my tube furnace.
And for my uses, any alkali metal salt will work, its just that I imagine that KCN would be easier to work with due to its lower solubility in
alcohol... heck I could probably get away with just using solution in water.
And I need lots of it, if what I am planning on doing works out (extraction of PGMs from recycled catalytic converters).
http://www.google.com/patents?id=84kiAAAAEBAJ&printsec=a...
Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in
beer.
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Eclectic
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Bromide/Bromate salt solutions would be much safer. Also, NaBr is not a DOT regulated hazmat.
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chloric1
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| Quote: | Originally posted by Eclectic
Bromide/Bromate salt solutions would be much safer. Also, NaBr is not a DOT regulated hazmat. |
And the bromate is cheaply and easily made from the bromide so the expense would be laughably affordable.
I do think cyanides have there place in experimental chemistry but I have made great pains to avoid using or making them. Having a 2 year old does
that. Damn there is an inorganic reduction done by fusing with KCN but I do not remember what. It is about the only interest I have in cyanide.
Fellow molecular manipulator
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kmno4
International Hazard
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BTW:
HCN/KCN thread already exists and I think there is no need to create another ones.
http://www.sciencemadness.org/talk/viewthread.php?tid=23
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