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Agari
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Theoretical Synthesis of Phosgene
I am going to try out an experiment on possibly synthesizing phosgene,and am actually going to wear a respirator unlike another member that died in
2010.
Note: So far,this is just a theory,what does the community think of this?
Chemicals:
-Crushed up TCCA tablets or calcium hypochlorite
-35% hydrochloric acid
-Activated carbon bought at a pharmacy
-95% Sulfuric acid
-85% Formic acid
-Water to neutralize the gas
Procedure:
-I will add the TCCA or CaCl2O2 to a 3-neck flask
-Will fill up a reaction tube with activated carbon halfway
-Add formic acid to another 3-neck flask
-I will then seal one end of the reaction tube with a 2-hole stopper and the other end with a 1-hole stopper.
-I will then attach an addition funnel to the 3-neck with formic acid and fill it with sulfuric acid, then completely seal 1 of the necks and cover
the other with a 1-hole stopper.The ratio of formic to sulfuric acid is 1:1.
-Attach another addition funnel with Hydrochloric acid to the 3-neck flask and seal one end completely and the other end with a 1-hole stopper.
-Connect the 1-hole end of the reaction tube to a tub of water using rubber tubing to hydralize any phosgene,if any, that exits.
-I will finally open the stopcocks of both addition funnels.
-I will then connect the 2 3-neck flasks to the reaction tube using rubber tubing and start heating the reaction tube with either a blowtorch or a
Bunsen burner.
Since the reaction is exothermic,I will use water to cool off the reaction tube and (hopefully) keep the temperature below 200C while above 110C.
The process(Theoretically):
The sulfuric acid will dehydrate the formic and result in carbon monoxide gas and the byproducts will remain in the flask.
If TCCA is used with the HCl,then the following happens:
3 HCl + C3Cl3N3O3 = 3 CNOH + 6 Cl
If CaCl2O2 is used:
CaCl2O2 + 4 HCl = CaCl2 + 2 H2O + 2 Cl2
Then,with the CO and Cl flowing into the reaction tube,the reaction:
CO+ Cl2-->COCl2
Will occur, and is catalyzed by the activated carbon.
The phosgene product then flows out of the reaction tube and into the water tub and is then decomposed to Carbon dioxide and hydrogen chloride:
COCl2 + H2O → CO2 + 2 HCl
Thus neutralizing the gas,well technically hydralizing.
As a precaution,I will use a respirator since phosgene is a level 4 health hazard on the NFPA 704 standard,meaning that small doses are enough to kill
or cause major residual damage.
This is just a theory,any criticism is welcome.
By the way,I heard what happened to myfanwy,I also heard that he was synthesizing hydrogen cyanide.
[Edited on 9-10-2015 by Agari]
[Edited on 9-10-2015 by Agari]
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phlogiston
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The title does not match your post. The title suggests you are only interested in theory (a thought experiment) but your post suggests that you intend
to execute the experiment.
Why would you want to?
If your only goal is to do this to be able to claim you did you will need a method of detecting the product, to prove that you actually were
sucesfull.
IMHO certain chemicals are not suitable for experimentation by amateurs. War gasses certainly fall into that category (not counting chlorine, which
can be handled in small quantities with sufficient care)
I can only hope you are not planning to do this in any residential area or location where other people (or animals) could be present.
Consider if your method of neutralizing the product is sufficiently effective and fail-safe.
[Edited on 9-10-2015 by phlogiston]
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Dr.Bob
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On the theoretical side, what is the reaction rate of the reaction
CO+ Cl2-->COCl2
If it is not nearly instant, then trying to make it in a flow system, without ways to measure and control the flow, concentration, and reaction time
of the gases, it will be hard to make much useful phosgene. Most people using small amounts of it now use either diphosgene or triphosgene (see
wikipedia or Aldrich's website) as replacements, which are easier to measure, store, handle, and safely use than phosgene. I have used all three and
would use triphosgene any day over a cylinder of phosgene (we had ~100 pounds of it in the lab in grad school) or even a solution of it in a solvent
(which you can buy from some vendors) or any other method of making it. And there are somewhat more practical ways of making them which are safer
than the method above. Still not easy, but still better.
Also, many reactions that needs phosgene can be redesigned for other more practical reagents or methods. But for some reactions, nothing is better,
I will admit.
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Agari
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Quote: Originally posted by phlogiston ![](images/xpblue/lastpost.gif) | The title does not match your post. The title suggests you are only interested in theory (a thought experiment) but your post suggests that you intend
to execute the experiment.
Why would you want to?
If your only goal is to do this to be able to claim you did you will need a method of detecting the product, to prove that you actually were
sucesfull.
IMHO certain chemicals are not suitable for experimentation by amateurs. War gasses certainly fall into that category (not counting chlorine, which
can be handled in small quantities with sufficient care)
I can only hope you are not planning to do this in any residential area or location where other people (or animals) could be present.
Consider if your method of neutralizing the product is sufficiently effective and fail-safe.
[Edited on 9-10-2015 by phlogiston] |
I will use small amounts of the acids and TCCA/HCl,and possibly use a detector to confirm that synthesis was successful somewhere along the line
before hydrolysis occurs. I am not sure whether hydrolysis is a very effective neutralization method,but it should reduce the amount of gas to a level
that does not present a threat to the surroundings,or do it inside but ventilate the area well.
https://www.youtube.com/v/K5NuqpdYDhE
[Edited on 9-10-2015 by Agari]
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clearly_not_atara
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Diphosgene via methyl formate + Cl2/hv sounds like a massive win relative to other methods, if you have the appropriate equipment, that is. Obviously
do not attempt the procedure without reading the original reference; in particular, do not attempt to simply substitute methyl
formate for methyl chloroformate in the OrgSyn procedure unless you have consulted other references which use specifically methyl formate.
Methyl formate is relatively easy to produce, but I would avoid the Fischer esterification; prefer the MeBr + NaHCO2 to avoid generating CO gas.
Quote: | If it is not nearly instant, then trying to make it in a flow system, without ways to measure and control the flow, concentration, and reaction time
of the gases, it will be hard to make much useful phosgene. |
In addition, be aware that CO is generally an underrated toxicant. Your system as described has very little in the way of containment or detection for
CO and I am concerned that you have not adequately considered the risks of working with this odorless, colorless, extremely toxic,
insoluble-in-almost-everything gas.
In fact if you run the reaction as you have described it your CO will pass through the charcoal and the water and exit into your laboratory
atmosphere. Study the containment and safety procedures for carbon monoxide before proceeding.
[Edited on 9-10-2015 by clearly_not_atara]
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aga
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There is no actual stated Use for the lethal gas.
Perhaps you wish to scale up and kill a lot of people ?
That's the first thought that springs to mind.
Phosgene is not suited to Amateur Chemistry at all.
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clearly_not_atara
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Quote: | [quote=aga] There is no actual stated Use for the lethal gas. [...] Phosgene is not suited to Amateur Chemistry at all. |
I object. Phosgene, if properly handled, can render the synthesis of many otherwise inaccessible compounds -- including 2-oxazolidinones, cyclic and
acyclic alkyl carbonates, acyl/imidoyl/oxalyl chlorides, chloroformates, BOC/tBOC/fMOC-protected amines/alcohols, peralkylated
amidines/guanidines/ureas, and oddities like isatoic anhydride -- possible from stable and cheap precursors. Alternatives like SOCl2 are similarly
difficult to prepare and carry their own hazards.
At worst phosgene can be quantitatively converted to carbonyl-diimidazole, a relatively safe and mostly stable coupling reagent (can prepare esters,
amides, thioesters, anhydrides).
Of course you are more likely to end up synthesizing carbonyl-dichemist if you aren't careful. I wouldn't fuck with it, myself.
[Edited on 9-10-2015 by clearly_not_atara]
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Agari
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Quote: |
I object. Phosgene, if properly handled, can render the synthesis of many otherwise inaccessible compounds -- including 2-oxazolidinones, cyclic and
acyclic alkyl carbonates, acyl/imidoyl/oxalyl chlorides, chloroformates, BOC/tBOC/fMOC-protected amines/alcohols, peralkylated
amidines/guanidines/ureas, and oddities like isatoic anhydride -- possible from stable and cheap precursors. Alternatives like SOCl2 are similarly
difficult to prepare and carry their own hazards.
At worst phosgene can be quantitatively converted to carbonyl-diimidazole, a relatively safe and mostly stable coupling reagent (can prepare esters,
amides, thioesters, anhydrides).
Of course you are more likely to end up synthesizing carbonyl-dichemist if you aren't careful. I wouldn't fuck with it, myself.
[Edited on 9-10-2015 by clearly_not_atara] |
Hmm,that sounds rather interesting, any way to increase phosgene yield for something like that? While I am unlikely to actually be able to prepare
those compounds,my initial intended use for the gas was to pipe it over into a concentrated ammonia solution to obtain urea,but I later found out that
I would need anhydrous ammonia otherwise most of the gas will be hydrolyzed.
Edit:If I can't increase the yield in any way,I guess I will have to buy a generator from Sigma Aldrich's site.
[Edited on 10-10-2015 by Agari]
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careysub
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Check out my recent post on the hazard of phosgene, compared to hydrogen cyanide:
http://www.sciencemadness.org/talk/viewthread.php?tid=13590
Phosgene is much more dangerous than hydrogen cyanide due to the fact that phosgene is a cumulative poison, and cyanide isn't.
Phosgene is a very useful reagent, widely used in industry.
But it should only be produced and consumed in a carefully set-up closed system, with provision against any release (an alkali/water solution trap),
and with suitable respirator protection (separate air supply, an efficient fume hood, or a mask with a filter known to be effective against phosgene)
since accidents happen.
Phosgene has little odor, provides no warning signs, produces no symptoms for up to 48 hours, and once they appear you are already a dead man. There
is no treatment.
A phosgene detection badge would be nice also (commercially available).
You can prepare your own with accessible reagents (this is from Sartori's "The War Gases"):
"Method using Dimethyl Amino Benzaldehyde—Diphenylamine
Paper. Phosgene, even if present in traces in the air, can be
detected by means of papers prepared with dimethyl amino
benzaldehyde and diphenylamine.
These papers are prepared by immersing strips of filter paper
in a solution of 5 gm. />-dimethyl-amino-benzaldehyde and 5 gm.
diphenylamine in 100 ml. ethyl alcohol and allowing them to dry
in a dark place, or better still, according to Suchier, in an
atmosphere of carbon dioxide. By exposing these papers, which
are originally white or pale straw-yellow, to an atmosphere
containing phosgene, an orange-yellow colouration is produced in
a few seconds, the intensity of the colour varying with the
concentration of phosgene. This change of colour is also observed
in presence of chlorine or hydrochloric acid.
It is possible to detect phosgene at a concentration of 4 mgm.
per cu. m. of air"
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Agari
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Quote: Originally posted by careysub ![](images/xpblue/lastpost.gif) | Check out my recent post on the hazard of phosgene, compared to hydrogen cyanide:
http://www.sciencemadness.org/talk/viewthread.php?tid=13590
Phosgene is much more dangerous than hydrogen cyanide due to the fact that phosgene is a cumulative poison, and cyanide isn't.
Phosgene is a very useful reagent, widely used in industry.
But it should only be produced and consumed in a carefully set-up closed system, with provision against any release (an alkali/water solution trap),
and with suitable respirator protection (separate air supply, an efficient fume hood, or a mask with a filter known to be effective against phosgene)
since accidents happen.
Phosgene has little odor, provides no warning signs, produces no symptoms for up to 48 hours, and once they appear you are already a dead man. There
is no treatment.
A phosgene detection badge would be nice also (commercially available).
You can prepare your own with accessible reagents (this is from Sartori's "The War Gases"):
"Method using Dimethyl Amino Benzaldehyde—Diphenylamine
Paper. Phosgene, even if present in traces in the air, can be
detected by means of papers prepared with dimethyl amino
benzaldehyde and diphenylamine.
These papers are prepared by immersing strips of filter paper
in a solution of 5 gm. />-dimethyl-amino-benzaldehyde and 5 gm.
diphenylamine in 100 ml. ethyl alcohol and allowing them to dry
in a dark place, or better still, according to Suchier, in an
atmosphere of carbon dioxide. By exposing these papers, which
are originally white or pale straw-yellow, to an atmosphere
containing phosgene, an orange-yellow colouration is produced in
a few seconds, the intensity of the colour varying with the
concentration of phosgene. This change of colour is also observed
in presence of chlorine or hydrochloric acid.
It is possible to detect phosgene at a concentration of 4 mgm.
per cu. m. of air" |
If you read my original post,I stated that I was going to use a respirator,though I am not sure if mine is effective vs phosgene. As for detection
addressed in an above reply,I was going to use a safe-air badge, which I will order tomorrow online. It is quite late where I live,I will try to make
phosgene detection paper tomorrow if I can get my hands on the reagents.
[Edited on 10-10-2015 by Agari]
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BromicAcid
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Quote: Originally posted by Agari ![](images/xpblue/lastpost.gif) |
-Water to neutralize the gas
-Connect the 1-hole end of the reaction tube to a tub of water using rubber tubing to hydralize any phosgene,if any, that exits.
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I... there is a very real chance you could die with this level of misunderstanding. You're using water to scrub your exit gasses... Carbon monoxide
will not scrub with water and your mask likely won't help either. Chlorine will not scrub with water, the solubility is actually surprisingly low in
plain old water, plus it may make it past your filter. And phosgene <b> will not scrub with water</b>. Phosgene is actually not very
reactive with water at all and can be dissolved in water without reaction (and is only very slightly soluble). Please stop using the internet and go
out and buy a book, get a reliable primary reference and stick to that. The belief that phosgene is rapidly hydrolyzed is ridiculously wide-spread
and completely false.
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Agari
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Quote: Originally posted by BromicAcid ![](images/xpblue/lastpost.gif) | Quote: Originally posted by Agari ![](images/xpblue/lastpost.gif) |
-Water to neutralize the gas
-Connect the 1-hole end of the reaction tube to a tub of water using rubber tubing to hydralize any phosgene,if any, that exits.
|
I... there is a very real chance you could die with this level of misunderstanding. You're using water to scrub your exit gasses... Carbon monoxide
will not scrub with water and your mask likely won't help either. Chlorine will not scrub with water, the solubility is actually surprisingly low in
plain old water, plus it may make it past your filter. And phosgene <b> will not scrub with water</b>. Phosgene is actually not very
reactive with water at all and can be dissolved in water without reaction (and is only very slightly soluble). Please stop using the internet and go
out and buy a book, get a reliable primary reference and stick to that. The belief that phosgene is rapidly hydrolyzed is ridiculously wide-spread
and completely false. |
Mmmk,I was not actually planning on scrubbing chlorine and carbon monoxide,just the phosgene,oh well,so long for that.
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careysub
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A two stage scrubbing system using NaOH/sodium thiosulfate and (separately) KOH/KMnO4 should scrub phosgene, chlorine and carbon monoxide.
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Agari
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Quote: Originally posted by careysub ![](images/xpblue/lastpost.gif) | A two stage scrubbing system using NaOH/sodium thiosulfate and (separately) KOH/KMnO4 should scrub phosgene, chlorine and carbon monoxide.
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I will consider that,I know that NaOH will scrub chlorine and KMnO4 will oxidize the CO,and phosgene does decompose with NaOH.
[Edited on 10-10-2015 by Agari]
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clearly_not_atara
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Quote: | Hmm,that sounds rather interesting, any way to increase phosgene yield for something like that? While I am unlikely to actually be able to prepare
those compounds,my initial intended use for the gas was to pipe it over into a concentrated ammonia solution to obtain urea,but I later found out that
I would need anhydrous ammonia otherwise most of the gas will be hydrolyzed.
Edit:If I can't increase the yield in any way,I guess I will have to buy a generator from Sigma Aldrich's site.
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Orgsyn has a procedure:
http://www.orgsyn.org/demo.aspx?prep=cv5p0201
I suggest an excess of imidazole; better safe than acylated. I (and everyone else here) cannot stress enough the extreme danger you're putting
yourself into.
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phlogiston
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Doesn't know if his scrubber is effective at all ... check
Does not know if his respirator is any good for the purpose ... check
Quote: |
I was going to use a respirator,though I am not sure if mine is effective vs phosgene |
Completely ignores the other highly poisonous gasses being produced... check
Quote: |
I was not actually planning on scrubbing chlorine and carbon monoxide |
And is already planning to scale up before he even started...
Quote: | Hmm,that sounds rather interesting, any way to increase phosgene yield |
At least you did one thing right, which was posting here before actually doing this. It may safe your life, because you are certainly on a dangerous
path.
First, consider whether you really want to pursue this. Is making urea truly worth it (considering it is cheap and should be easily available almost
anywhere)??
Then, if you decide you do, spend the next year doing nothing but planning and thinking it over before doing anything. Pay extreme consideration to
detail and possible failure mechanisms. How do you check if your respirator seals well? Can the tubing on your scrubber come lose in case of
overpressure? What is the capacity of the scrubber? What if you trip, hit your head and lose consciousness? Where does your fumehood vent extracted
fumes? How are you controlling the gasflow of the reactants? etc. etc. etc.
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Metacelsus
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Quote: Originally posted by Agari ![](images/xpblue/lastpost.gif) | my initial intended use for the gas was to pipe it over into a concentrated ammonia solution to obtain urea |
If you're making phosgene, at least use it for something better than making urea. Make something that can only be made with phosgene, like
ethyl chloroformate, from reaction with ethanol. (Don't say you can't prepare that.)
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BromicAcid
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If you are hell-bent on making phosgene you should explore different routes. Working with a single gas is doable at home but taming two gasses to
make a third is begging for disaster. Older (much older) methods started from chloroform or carbon tetrachloride. It may suit you better to start
there, at least you could better meter your reagents that way plus you wont have unreacted chlorine and carbon monoxide coming out the back end.
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careysub
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While doing a little research on this subject, I see that oxalyl chloride can decompose into phosgene and carbon monoxide in various side reactions.
I did not know that.
It would seem anyone working with oxalyl chloride should at least have the respirator/fume hood in place and a phosgene badge also.
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jnik
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There is another possible way (probably more safe) to use triphosgene, which is a white-crystall solid with melting point near 80 C. After hydrolysis
it will give you the desired compoud - phosgene. Such a solid substance much easier to handle.
To produce it you need to chlorinate dimethylcarbonate in a flask under irradiation of sunlight spectrum lamp with increase of temperature step by
step from 40 to 80 C. Byproducts (HCl and unreacted chlorine) coud be neutralised with NaOH + Na2SO3 solution. End of reaction - green colour of gas
phase above the liquid surface / yellow colour of the reaction mixture. Possible issues - crystallization of triphosgene in connection tubes and
condenser.
Safety:
Actually phosgene is not THAT bad, so it will not kill you immediatly (good news). You have some time to neutralise yourself and lab. But be careful,
phosgene will decrease your ability to sence it after exposure!!! (bad news) If you smell the substance, then you must stop process and find a
leakage.
Implementing such a proccess you shoud prepare your best friend: respirator, gloves, neutralisation solutions (5-10% NH3 in water and/or organic
amines like diethylamine) and alcohol (to inhale and drink).
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Agari
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Quote: Originally posted by jnik ![](images/xpblue/lastpost.gif) | There is another possible way (probably more safe) to use triphosgene, which is a white-crystall solid with melting point near 80 C. After hydrolysis
it will give you the desired compoud - phosgene. Such a solid substance much easier to handle.
To produce it you need to chlorinate dimethylcarbonate in a flask under irradiation of sunlight spectrum lamp with increase of temperature step by
step from 40 to 80 C. Byproducts (HCl and unreacted chlorine) coud be neutralised with NaOH + Na2SO3 solution. End of reaction - green colour of gas
phase above the liquid surface / yellow colour of the reaction mixture. Possible issues - crystallization of triphosgene in connection tubes and
condenser.
Safety:
Actually phosgene is not THAT bad, so it will not kill you immediatly (good news). You have some time to neutralise yourself and lab. But be careful,
phosgene will decrease your ability to sence it after exposure!!! (bad news) If you smell the substance, then you must stop process and find a
leakage.
Implementing such a proccess you shoud prepare your best friend: respirator, gloves, neutralisation solutions (5-10% NH3 in water and/or organic
amines like diethylamine) and alcohol (to inhale and drink). |
I have serious doubts about inhaling ethanol when phosgene may be present in my lungs,correct me if I am wrong,but I'm pretty sure it will form HCl
and other compounds.
Edit:Or MAYBE triphosgene is commercially available,nevermind,dimethyl carbonate is also commercially available.
[Edited on 10-10-2015 by Agari]
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CharlieA
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50-some odd years ago, I used phosgene in a synthesis of (I don't remember) at a then-subsidiary of Sigma Chemical Co. IIRC, we purchased the phosgene
in small cylinders. In hindsight, I'm amazed that I didn't die in the laboratory, and now I'm a proud 12+ year cancer survivor. My oncologist thinks
my smoking was the cause; my radiologist thinks my lab work was a cause. When I think of how I (we) operated in the lab (e.g., I pipetted just about
anything by mouth; after a large (several kg) filtration involving EtOH and Et2O in a small enclosure I was bombed out of my head). I guess what I am
trying to say is that it seems to me that many of our members do not give enough consideration to the hazards of chemistry. Although I am setting up a
home lab after 35+ years of no chemical activity, I hope I am going slowly and giving careful consideration to my actions. Of course, maybe I am going
too slowly...
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Agari
Banned
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Location: The Amine Group
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Mood: Lowest Oxidation State
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Quote: Originally posted by CharlieA ![](images/xpblue/lastpost.gif) | 50-some odd years ago, I used phosgene in a synthesis of (I don't remember) at a then-subsidiary of Sigma Chemical Co. IIRC, we purchased the phosgene
in small cylinders. In hindsight, I'm amazed that I didn't die in the laboratory, and now I'm a proud 12+ year cancer survivor. My oncologist thinks
my smoking was the cause; my radiologist thinks my lab work was a cause. When I think of how I (we) operated in the lab (e.g., I pipetted just about
anything by mouth; after a large (several kg) filtration involving EtOH and Et2O in a small enclosure I was bombed out of my head). I guess what I am
trying to say is that it seems to me that many of our members do not give enough consideration to the hazards of chemistry. Although I am setting up a
home lab after 35+ years of no chemical activity, I hope I am going slowly and giving careful consideration to my actions. Of course, maybe I am going
too slowly... |
Yep,TOTALLY legit,TOTALLY not full of crap.
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Bot0nist
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Registered: 15-2-2011
Location: Right behind you.
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Mood: Streching my cotyledons.
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CharlieA, in this thread, I think your plea for a safe pace is called for, and that comes from an amateur whose intrest began with energetic
materials.
I do hope the OP reconsider his quest, or at least takes a very slow pace in learning and applying the vast amount of knowledge and care that an
amatuer hobbiest must surely have in order to even try to safely produce and work with an insidious killer like phosgene. Most amateurs and home
chemistry enthusiasts would not even consider attempting such things, myself included.
In my more careless experiances, I have had organic peroxides explode unexpectedly in close proximity, gassed myself with nitrogen oxides, and even
flirted with hazards such as hydrazine and azides, but still I would not have dared play with a devil like phosgene. And maybe some will say I am
exaggerating the risks of this gas.
Perhaps it is "Not THAT bad," sure, when compared to modern nerve agents and war gasses, but it can and will easily be the unsuspecting death of you,
and any poor soul unlucky enough to catch a few breaths of it. And that's if the attempt is successful. Carbon monoxide is a sneaky killer as well,
and even a system failure resulting in a room full of chlorine could spell disaster.
[Edited on 11-10-2015 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Bot0nist
International Hazard
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Posts: 1559
Registered: 15-2-2011
Location: Right behind you.
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Mood: Streching my cotyledons.
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I do hope your safety checks and PPE serve you as well as your sarcasm and disregard for what seemed to me to be honest and legitimate concern.
Good luck, and be safe Agari, and I mean that truely and with no ill will.
[Edited on 11-10-2015 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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