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testimento
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How can I test is the white solid a cyanide or a cyanate salt? I'm pretty sure it's cyanide but I would like to make sure.
I have safety solution made of little bit of sodium hydroxide and a scoop of calcium hypochlorite. The residual matters, like filtrate garbage, flasks
and other stuff will make bubbles and hiss so they make a reaction in there, could this be an indicator that the stuff is really cyanide?
[Edited on 6-11-2013 by testimento]
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Magpie
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see:
http://www.sciencemadness.org/talk/viewthread.php?tid=9128&a...
The single most important condition for a successful synthesis is good mixing - Nicodem
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Panache
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In relation to the reaction between chloroform, ammonia and potassium hydroxide, Gatterman (1937, see Sci Mad Library for download) refers
specifically to it. Interestingly i only just opened and read this thread in order to query with members the voracity of this claim, so it was
pleasant to note the post referring generally to chlorinated methanes reacting with ammonia and hydroxides. I feel that if gatterman specifically
referred to chloroform and KOH, there is an inherent implication that this is the best combination.
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charmander
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Hello. I have been following this forum for a few years now; just a lurker, but I would like some input from the more educated members. I have taken a
few chemistry classes, just finished orgo 1, so I know a little bit but not enough.
I've done Polverone synthesis of cyanide using sodium carbonate, cyanuric acid and charcoal. Everything went well and I have attained a product. The
crystals resemble sugar with a slightly tint of grey from the charcoal that slipped through the filters. The solution is very slippery much more than
sodium carbonate. But I need relatively pure cyanide and I’d like input on how to achieve it.
I will react the product with an acid and distill the hydrogen cyanide and hydrogen cyanate (Isocyanic acid). I have a respirator and this will be
done outside. This will remove charcoal and any sodium carbonate that was potently left, as well as any other byproducts, but not the cyanate.
The salts and acids of cyanide and cyanate have very similar properties. The solubility in alcohols and other solvents are really close. One
noticeable difference was the melting points of HNCO and HCN, -86 °C and -14°C respectively.
Would taking HNCO and HCN in a RBF and putting it over a freezing saturated brine solution cause the HCN to crystallize out?
Or does anyone have a better idea on have to separate cyanates from cyanides?
I was thinking of forming a cyanide complex and separating that way, I need to look into this a bit more. HNCO also turns into cyanuric acid at high
temps which is insoluble in water, but HCN probably will also polymerize to an extent and I REALLY hate even thinking about dealing with HCN as a gas.
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Magpie
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Take a read of the following, available through Google Books:
Allen’s Commercial Organic Analysis, vol VII
There's some information on treating with AgNO3 that will ppt out the cyanate but not the cyanide. It's in the chapter on Cyanogen.
The single most important condition for a successful synthesis is good mixing - Nicodem
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charmander
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Magpie, I read the section on cyanogens but I could not find the section on purifying cyanide. Maybe Google didn’t let me see all the pages. But I
think I figured it out. Here is the plan.
Obtain sodium cyanide and sodium cyanate by reacting the crude mixture obtained with Polverone cyanuric acid method with sulfuric acid and condensing
the gasses. Take the liquid hydrogen cyanide and hydrogen cyanate and pour it into ice cold solution of NaOH in denatured alcohol. The sodium cyanide
and sodium cyanate salts will precipitate out. Wash the crystals with cold ethanol.
Make a saturated solution of the cyanogens salts. Then add drop wise silver nitrate until all the silver cyanate precipitates out. Filter out the
silver cyanate.
The sodium cyanide solution will now contain NaNO3. NaNO3 is soluble in water and alcohol. So when adding denatured alcohol to the solution, only
sodium cyanide should precipitate out. The product should be pure sodium cyanide.
Now to recover the silver from the silver cyanate, add nitric acid to the solution. According to Wikipedia this should yield silver nitrate, carbon
dioxide and, ammonium nitrate. The silver could be recovered by heating the mixture and letting the salts decompose. Or ether could be used to
dissolve the silver nitrate and not the ammonium nitrate. Ether is kind of hard to get so what other solvent or procedure can be used to recover the
silver.
I just received my order of silver so I’ll try this procedure sometime soon and post the results.
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Magpie
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Quote: Originally posted by charmander  | Magpie, I read the section on cyanogens but I could not find the section on purifying cyanide. Maybe Google didn’t let me see all the pages. But I
think I figured it out. Here is the plan.
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I think that is what I hoped you would do, ie, figure out a plan from reading the Allen book. I don't recall there being a specific procedure for
separating the cyanate from cyanide.
I presume you have read my procedure in pre-pub for assaying cyanate. This may prove helpful.
Others can best advise you for recovering the silver. I have not done this yet.
Please be very careful handling cyanide. I have never handled HCN, only KCN. A good fume hood, outside work, and keeping the cyanide basic (whenever
possible) are my recommendations.
The single most important condition for a successful synthesis is good mixing - Nicodem
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charmander
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So I did some more research and I found the article on detecting cyanate with cobalt(2). It was in the Allen's Commercial Organic Analysis volume 7. I
guess last time I must have read in the wrong volume because this one is amazing, the older version or what ever I read had very little on cyanogens.
I downloaded a pdf version so that i can have it for life 
I had to make nitric acid at home so it took longer than usual to get the silver nitrate. The silver nitrate is in a 100ml solution and because of the
weather it has been taking forever to evaporate.
Heating the silver nitrate solution caused silver oxide and or silver metal to precipitate out so it looks like this might take a while to evaporate.
But this weather might be a good thing. If it stays cold then the hydrogen cyanide and cyanate should stay as a liquid, which is REAL good.
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testimento
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Does NaCN/HCN react with aluminium? I stored a portion of it outside overnight and the aluminium foil I placed to cover the pot had been eaten away,
literally corroded. I thought this could be some sort of HCN amalgation?
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charmander
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NaCN will react with aluminum and many other metals like gold and copper(which is why it is used in mining). HCN will not. HCN is usually stored in
aluminum tanks.
You should not store your cyanide salts in metal containers or in glass jars with metal lids.
I store mine in a glass jar with a HDPE cap, and then this is put in a plastic bag for easy and safe clean up just in case it fall and breaks.
Please be safe.
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DraconicAcid
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| Quote: Originally posted by testimento | | Does NaCN/HCN react with aluminium? I stored a portion of it outside overnight and the aluminium foil I placed to cover the pot had been eaten away,
literally corroded. I thought this could be some sort of HCN amalgation? |
It's not amalgamation, it's literally corroded. Strong bases will react with aluminum, due to the formation of aluminates.
2 NaCN + 2 Al + 8 H2O -> 2 NaAl(OH)4 + 3H2 + 2 HCN(g).
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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charmander
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I need advice. So while I was waiting for my silver nitrate to dry off, (Btw it took over a month for 150ml of water to evaporate and leave crystals
of silver nitrate. This must have been because of silver nitrate high solubility as well as the residual nitric acid left behind.) I tried making
cyanide from potassium ferricyanide. (Notice ferri not ferro). I attempted to make it this way before without success, but after getting some lab
experience with nitrated products I attempted the experiment again. I reacted 20 grams of potassium ferricyanide and 15 ml of about 70% sulfuric acid.
I distilled over about 7 ml of a clear liquid which should be hydrogen cyanide. With a dropper I transfer some of this to a solution of denatured
ethanol and sodium hydroxide. What should have happened was the sodium cyanide should have precipitated out, but something else took place. On the top
of the ethanol solution an oily layer formed that took on an orangeish red color. After giving it a few swirls the layer dissolved into the ethanol
solution giving the whole solution an orange color. There was no precipitant.
In another beaker I added the hydrogen cyanide to a solution of sodium hydroxide in water. There was a small color change and the hydrogen cyanide
seemed to dissolve into the solution. I then poured ethanol into the beaker but nothing precipitated. The solution then turned into the same orange
red color.
In a third beaker I dripped the hydrogen cyanide into distilled water. As each drop hit the water gas evolved from that area. The solution turned
slightly orange.
Being disappointed I took a 30 minute break. I left the sealed flask with the hydrogen cyanide in an ice bath. I come back and the hydrogen cyanide
turned a dark red/black color. I poured this into vial and sealed it to deal with it the next day. It was dark and I had to clean up.
The next day I look at the product and it solidified into a black solid cake. After I opened it I took a whiff and it was not a pleasant scent. Some
of the cake dried up on top into a light brown powder.
So I definitely formed hydrogen cyanide but it polymerized up. Can someone give my some advice on how to obtain the cyanide salt and prevent it from
polymerizing?
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Oscilllator
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Charmander read through this thread. The posts by Zan Divine contain the information looking for. In future, be sure to look through the thread to see
if your question has already been answered.
Also, sniffing jars of hydrogen cyanide is an extremely good way to get a darwin award.
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charmander
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I read it before, i guess i got to read it all over again.
I took a whiff about a foot and a half away from the jar after the used my hand to move the vapors towards me. My chem professor thought me that. It
seems safe enough for me.
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AJKOER
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| Quote: Originally posted by AJKOER | A simple direct and proven approach (but gaseous requiring precautions and use of an expensive catalyst), try to replicate the industrial Andrussow
process either on a micro scale or larger. Per Wiki, to quote:
"The Andrussow process is an industrial process for the production of hydrogen cyanide from methane and ammonia in the presence of oxygen and a
platinum catalyst.[1][2]
CH4 + NH3 + 1.5 O2 → HCN + 3 H2O
..... |
What I find interesting in the above reaction is it similarity to the Ostwald process for the production of NO also employing a platinum catalyst.
This observation was also noted by the author of my previously cited doctoral thesis (see page 5 at http://research.cems.umn.edu/schmidt/schmidtpapers/thesis/Sa... ). So what if NO formation provides a path to HCN creation? Assuming it is, in the
home lab, one can easily replace this step (and the use of a Pt catalyst) with just supplying a stream of NO to the combustion of an appropriate
hydrocarbon.
There is some support for this method based on research of removing NO waste gas by "reburning". See "NITROGEN OXIDE REBURNING WITH HYDROCARBON
FUELS", by Thomas E. Burch at https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/35_... . The author outlines the reaction mechanism as follows:
"Employing the mechanisms and senstivity analysis of Miller and Bowman (1989) along with calculations
conducted by Chen et al. (1989) it seems resonable to view reburning as possessing two major kinetic barriers. The first
barrier is the conversion of NO to HCN by combination with various hydrocarbon fragments such as
C + NO -> CN + O
CH + NO -> HCN + O
CH2 + NO -> HCNO + H
The accepted rate constants for these reactions are all within roughly one order of magnitude so the dominant
mechanism in the conversion of NO to HCN is strongly dependent on the relative concentrations of the reducing species produced. Regardless of which
mechanism dominates, there is general agreement that the end product is HCN, whether formed directly of by rapid conversion of intermediates such as
CN.
The second major kinetic obstacle appears to be oxidation of HCN via one of the following reactions:
HCN + OH -> HOCN + H
HCN + OH -> HNCO + H
HCN + O -> NCO + H
HCN+O -> NH + CO
Having accomplished this step the subsequent conversion to N atoms is rapid. N atoms are then recycled to
form NO or react with NO to form N2.
Using this two barrier concept many of the salient feactures of reburning can be interpreted."
The author also makes favorable comments suggesting the use of benzene in place of methane.
I am still thinking over exactly how to implement the underlying process, but I thought it was interesting enough to present. One embodiment, for
example, could be based on the ability of Nitric oxide to support and enhance combustion. So, perhaps placing burning benzene in an atmosphere of pure
NO in a closed vessel would form HCN. Addressing/limiting impurities would be an issue.
--------------------------------------------------------
A comment of preparing cyanide from cyanogen, per Atomistry.com on cyanogen to quote (link: http://www.google.com/url?sa=t&rct=j&q=atomistry.com... ):
"[Water] dissolves about four and a half times its volume of cyanogen gas, alcohol about twenty-three times its volume. Water, however, acts
chemically on cyanogen, causing the separation of a brown insoluble substance known as azulmic acid, and at the same time hydrolysing the cyanogen
(NC-CN), producing from it oxamide (H2NOC-CONH2), oxamic acid (HOOC-CONH2), oxalic acid (HOOC-COOH), and their ammonium salts; together with the
following compounds containing only one carbon atom: hydrocyanic acid, urea (H2N-CO-NH2), and ammonium carbonate. When cyanogen is passed into water
at 0° C., however, the reaction is simple, hydrocyanic and cyanic acids being formed thus:
(CN)2 + H2O = HCN + HCNO. "
--------------------------------------------
Also, per Atomistry.com CNCl does not decompose in water as was previously indicated.
[Edited on 14-3-2014 by AJKOER]
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Nitrous2000
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| Quote: Originally posted by charmander | I read it before, i guess i got to read it all over again.
I took a whiff about a foot and a half away from the jar after the used my hand to move the vapors towards me. My chem professor thought me that. It
seems safe enough for me. |
Can YOU smell cyanide gas?
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AJKOER
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OK, I an across a preparation path using available, mostly households, starting materials. To quote from Atomistry.com on HCN (link: http://carbon.atomistry.com/hydrocyanic_acid.html ):
"Bergmann has shown that when ammonia is passed over carbon heated to about 1300° C., 90 per cent, of it is converted into HCN. The reaction is
endothermic, its heat being -39,500 calories. A modification of this reaction is that of Roeder and Grunwald, who pass a mixture of ammonia, and
nitrous oxide over heated carbon, the reaction being:
2NH3 + N2O + 4C = 4HCN + H2O - 58,000 calories.
Owing to the heat of decomposition of nitrous oxide, which is endothermic, and the heat of formation of steam, it is not necessary to heat the carbon
to so high a temperature as in the former case; indeed the yield of hydrogen cyanide is nearly quantitative when the temperature of the carbon is but
450° C. "
As I have recently purchased N2O and can dispense a stream of gas using the Nitrous oxide whipper, one possible embodiment would be as follows:
1. Place aqueous ammonia in a whipper and infuse with N2O via a 8 gram cartridge.
2. From a charcoal grill, place hot coals in a pipe.
3. Direct and release the N2O/NH3 gas from the whipper through the pipe.
4. Direct the exit gases from the pipe containing HCN into a solution of NaOH.
Points to be resolved:
1. On the chemistry, is water vapor in the gas mix an issue (and a drying step would be required).
2. Do the coals have to be continually heated while in the pipe.
3. Forming a seal with the exit nozzle from the whipper onto the pipe may be a problem.
-------------------------------
A more limited but even easier embodiment (but not necessarily safer) would be to heat outdoors Carbon, Ammonia and N2O in an expandable container in
a microwave for multiple short burst, followed by cooling, to avoid containment rupture. Note, allowing for gaseous expansion favors increase yield
(the formation equation indicates that 3 moles of gas become 4, and there could also be some N2O decomposition where 2 moles become 3, which is
accompanied by a loud knock like noise) and reduced risk of rupture.
Finally, add NaOH upon completion for NaCN in minutes (or possible death, if one is not performing this experiment as recommended, or indoors without
a gas mask and a cyanide antidote kit).
This is probably also a good reason to avoid thus experimenting with N2O and compounds rich in Carbon, Hydrogen and/or Nitrogen, and then expecting
something possibly not too lethal.
[Edit] Do not attempt to make this a one pot synthesis and heat NaOH (or, Na2CO3 plus water vapor) in an atmosphere of N2O in a microwave. As I have
noted previously on SM, this could produce quite a fireworks display with potential containment breach. See discussion at http://www.sciencemadness.org/talk/viewthread.php?tid=32334#... and references cited there in. Also I suspect, ignoring safety and feasibility
issues, that only an impure NaCN could be so formed.
[Edited on 4-10-2014 by AJKOER]
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Dan Vizine
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Hi Charmander,
My advice is don't think of it as a gas. Think of it as a volatile liquid.
The gas phase is just a fleeting moment, it turns to liquid very easily with circulating ice water. Besides, you need the gas phase, it's the only
practical method that doesn't incur huge losses.
Here is a critical point that I know to be true, but the reason mystifies me:
If you collect the HCN as it distills out of the ferricyanide/acid pot, it stays water clear. If you then add it to stirred aqueous NaOH, you get a
clear solution of NaCN. However, if you lead the condensed HCN from the reaction directly into stirred, aqueous base it will turn
very, very dark and quickly. It's clearly a polymerization issue of some kind. Offhand, the two processes don't seem all that different, but they
clearly are.
One other point. HCN is an endothermic compound and as such, may decompose spontaneously (ESPECIALLY if contaminated with cyanide
anions*). This is prevented by addition of a small amount of H2SO4. I think I give a recommended level in my earlier posts. it's a per cent or two,
roughly. I add it to the collection flask before the reaction even begins. Keep the flask at 0 C.
* Your glassware must not have any basic residues left in it!
[Edited on 9-10-2014 by Dan Vizine]
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Dr.Arz
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What kind of protective measures you use when you work with cyanides? I have read that some people here actually dont even have any face gear or
ventilation and some have even sniffed HCN flasks. 
So am I just too paranoid about toxicity of cyanides or what? I have been thinking how can I handle them safely without slightest risk of harming
myself or others. Only really safe thing is to make a fume hood outdoors, put a large duct fan on top of it and add a long, at least 2-3 meters
chimney from pvc tube that will suck everything out from the hood up to the sky. Still after this I want to wear high grade respirator mask, long
nitrile gloves and maybe even full body pp suit just in case. Also to keep hypochlorite liquid near to rinse and wash all parts that were in contact
with any cyanides and discard all wastewater carefully. Im afraid draining them to sewer because gases can absorb to floor drain water locks and
evaporate insides. Problems that its getting really cold outsides so I got to either wait for summer or then figure out some safe way. My worst
nightmare is that any of the distilling equipment implode or fall apart during vacuum distillations, even I use only top grade new-bought glass and
extra precautions with applying heat and cold or any stresses on them, it is just too much of thinking hundreds of grams of cyanides bursting into a
cloud of aerosol.
[Edited on 19-10-2014 by Dr.Arz]
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careysub
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| Quote: Originally posted by Dan Vizine |
...
Here is a critical point that I know to be true, but the reason mystifies me:
If you collect the HCN as it distills out of the ferricyanide/acid pot, it stays water clear. If you then add it to stirred aqueous NaOH, you get a
clear solution of NaCN. However, if you lead the condensed HCN from the reaction directly into stirred, aqueous base it will turn
very, very dark and quickly. It's clearly a polymerization issue of some kind. Offhand, the two processes don't seem all that different, but they
clearly are.
...
[Edited on 9-10-2014 by Dan Vizine] |
I did not know this would happen - but I can postulate what is probably going on.
HCN polymerizes in the presence of bases, a process that is autocatalytic, but not (initially) a very high rate reaction.
When the HCN is being condensed into NaOH solution it is being very slowly added to a huge excess of base, and has time for the polymerization process
to start, and once it has commenced very far you are toast.
When you add a mass of liquid HCN all at once to NaOH solution there is never an excess of base, and the NaOH is neutralized immediately.
The Russians stabilized their HCN rocket warheads with phosphoric acid, so that alkaline conditions were never encountered.
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careysub
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| Quote: | What kind of protective measures you use when you work with cyanides? I have read that some people here actually dont even have any face gear or
ventilation and some have even sniffed HCN flasks.
So am I just too paranoid about toxicity of cyanides or what?
|
HCN is very poisonous to be sure, if absorbed by the body all at once 25 mg - basically one drop - can be fatal. The worst aspect of cyanide
poisoning, should it occur, is that is extremely fast. You would be unable to help yourself. (Because of the way it works cyanide is probably the
fastest poison there is.)
That said - it is unique among strong poisons in that it is not only NOT CUMULATIVE, your body has a detoxification mechanism built in so that
sufficiently low exposure rates are actually harmless. Cyanide is widely distributed in plants in low concentrations, and mammals evolved the ability
to destroy it.
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).
HCN is detectable in air at a threshold concentration of about 0.7 mg/M^3. But people vary in sensitivity, some people don't detect it well, and
people quickly become desensitized to the odor. Concentrations of up to 40 mg/M^3 can be tolerated indefinitely, but four times this will kill you in
half an hour, five times will kill you in ten minutes.
Don't smell an HCN flask. Ever.
If you want to find out what HCN smells like I suggest putting a drop (~40 mg) in a liter of water and smelling that. No toxic exposure is possible in
that situation.
| Quote: | | I have been thinking how can I handle them safely without slightest risk of harming myself or others. Only really safe thing is to make a fume hood
outdoors, put a large duct fan on top of it and add a long, at least 2-3 meters chimney from pvc tube that will suck everything out from the hood up
to the sky. Still after this I want to wear high grade respirator mask, long nitrile gloves and maybe even full body pp suit just in case. Also to
keep hypochlorite liquid near to rinse and wash all parts that were in contact with any cyanides and discard all wastewater carefully. Im afraid
draining them to sewer because gases can absorb to floor drain water locks and evaporate insides. Problems that its getting really cold outsides so I
got to either wait for summer or then figure out some safe way. |
Get a chemical respirator (half-mask is fine) with either a general purpose or acid gas cartridge. Others are not suitable.
Wear good chemical gloves.
Have a basin of 0.5% hypochlorite solution (household bleach diluted 10:1) at the ready at all times, with the plan of dunking all of your equipment
in it when you are done. This will completely destroy all cyanide immediately.
A PP (Tyvek) suit is a good idea when working with any caustic material, if only to protect your clothes.
I think the chimney thing is unnecessary if working outdoors, but I would use some forced air circulation scheme (a fan and a box) to ensure air flows
away from you.
| Quote: | My worst nightmare is that any of the distilling equipment implode or fall apart during vacuum distillations, even I use only top grade new-bought
glass and extra precautions with applying heat and cold or any stresses on them, it is just too much of thinking hundreds of grams of cyanides
bursting into a cloud of aerosol.
|
Design your experiments appropriately. Don't do vacuum distillations with hundreds of grams of cyanide, for example.
[Edited on 19-10-2014 by careysub]
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Dan Vizine
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| Quote: Originally posted by careysub |
When you add a mass of liquid HCN all at once to NaOH solution there is never an excess of base, and the NaOH is neutralized immediately.
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Ah, but the answer isn't that simple. I always add the liquid cyanide (previously collected) in a dropwise fashion to cold, stirred base. The process
takes at least 45 - 60 min for 100 g of HCN (to avoid exotherms which may boil off some HCN).
It is very similar to the dropwise distillation to cold, stirred base straight from the condenser, which causes darkening quite quickly.
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careysub
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| Quote: Originally posted by Dan Vizine | | Quote: Originally posted by careysub |
When you add a mass of liquid HCN all at once to NaOH solution there is never an excess of base, and the NaOH is neutralized immediately.
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Ah, but the answer isn't that simple. I always add the liquid cyanide (previously collected) in a dropwise fashion to cold, stirred base. The process
takes at least 45 - 60 min for 100 g of HCN (to avoid exotherms which may boil off some HCN).
It is very similar to the dropwise distillation to cold, stirred base straight from the condenser, which causes darkening quite quickly.
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Do you add any stabilization acid to the distillation flask or product afterward?
[Edited on 19-10-2014 by careysub]
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careysub
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It would be very interesting to get hold of this article (in English translation):
Völker, T. 1960. Polymeric hydrogen cyanide. Angew. Chemic 72, 379–384.
It seems to be the principal reference on the subject from the perspective of preparative and industrial chemistry.
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Dan Vizine
National Hazard
Posts: 628
Registered: 4-4-2014
Location: Tonawanda, New York
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| Quote: Originally posted by careysub | | Quote: Originally posted by Dan Vizine | | Quote: Originally posted by careysub |
When you add a mass of liquid HCN all at once to NaOH solution there is never an excess of base, and the NaOH is neutralized immediately.
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Ah, but the answer isn't that simple. I always add the liquid cyanide (previously collected) in a dropwise fashion to cold, stirred base. The process
takes at least 45 - 60 min for 100 g of HCN (to avoid exotherms which may boil off some HCN).
It is very similar to the dropwise distillation to cold, stirred base straight from the condenser, which causes darkening quite quickly.
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Do you add any stabilization acid to the distillation flask or product afterward?
[Edited on 19-10-2014 by careysub] |
I'm a bit red-faced here....I've done it both ways. And both ways gave the same results. In my first preps, I didn't appreciate the polymerization
danger. Results were that direct addition to base gave dark products while collection first and subsequent addition to cold, stirred base gave nearly
colorless product. With stabilizer added to the collection I also got a nearly colorless product.
There is no need to add stabilizer to the solution after neutralization. As aqueous NaCN, it can no longer violently polymerize.
Actually, a slight yellow color could be seen in the solutions, but nothing of any significance. And when you have concentrated aqueous cyanide, you
aren't surprised to see traces of color, after all, it's only quasi-stable.
The direct addition solutions were nearly black.
It's almost as though a reactive non-condensable gas is present in the direct addition trials, and it has escaped from the condensed liquid. That fits
the facts, physically at least, but I can't come up with such a species likely to fit that description. The ambident nature of the cyanide group
doesn't seem to have any significance here either.
[Edited on 21-10-2014 by Dan Vizine]
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