Picric-A
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Interesting Spectation
I was experimenting today with burning hydrogen. As most people know it burns with a near colourless flame, completly clean burning and i always find
the water produced has a ozone type smell (due to the ~4% H2O2 produced) which i find very pleasant.
Now i decided i would try buring the hydrogen in different atmosphears (i tryed I2, Br2, pure O2, CO2 ect..). I moved on to try buring the H2 in an
atmosphear of CHCl3, knowing that it doesnt burn on its own. What followed was most spectacular;
A delivery tube of burinng H2 was lowered into a gas jar saturated with the CHCl3 vapour. The flame instantly turned from colourless (with a hint of
orange) to a lovely blue colour and then white and yellow fumes started to be produced.
Now i can guess the white fumes are HCl, a possible decomposition product. Maybe some phosgene was formed as well (this was performed in a fume
cupboard). Anybody have an idea of the yellow gas? Elemental chlorine by any chance? I doubt it as it was a lot darker than chlorine is, an almost
chlorine dioxide colour....
Any feedback will be usefull, thanks!
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Barium
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Which part of this is organic chemistry?
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rrkss
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The fact that he is reacting hydrogen with trichloromethane.
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Mr. Wizard
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Just to get some facts straight; you were burning this H2 in air, and you lowered the burning flame into a container that was open to the air and
contained chloroform vapor at saturation at about 20C?
It's partial pressure at that temperature would be around 175 mmHg. Out of 760 for normal air. This is less than 25% chloroform and mostly air.
It does sound very interesting. It could be anything including nitric oxide to ammonium chloride mixed with HCl or Nitric Acid. Is the gas acidic? Is
the gas an oxidizer, will it turn damp KI / starch paper blue or black?
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Picric-A
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At time i did not try contain/ keep the gas for testing as i feared the phosgene potentially produced.
I will today however do some more tests on this and test the properties of the gasses produced.
I will also try the same with with dichloromethane and carbon tetrachloride.
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smuv
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Chlorocarbons burn with a blue/green flame. Hydrogen has nothing to do with it.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Picric-A
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If it was simply the chloroform burning, how come chloroform does not burn on itself, when supported by a wick ect...?
Also can you explain the weird yellow gas produced? The chloroform was A.R and the hydrogen that from a L.B.
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Mr. Wizard
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Most chlorinated hydrocarbons that will even burn, burn with a smokey soot filled flame, and have a yellow or reddish flame, in my experience. The
green blue color you are referring to is from copper reacting with halogens. It is a very sensitive test, and was used to detect Freon leaks in air
conditioning systems before the newer non flame methods were used. Even then, too much of the halogenated hydrocarbon will swamp this color and cause
a soot filled flame that looks yellow or red. This has been been my experience with things burning in air.
To state hydrogen has nothing to do with it may be premature. Hydrogen can maintain combustion in a very wide range of variables and oxygen
concentrations. I understand it was used as an additive in U-2 jet engines to maintain combustion at it's over-flight altitude. They will admit to
being able to fly at 70,000 feet.
http://www.prouty.org/sabotage.html
This little tid-bit about hydrogen does not appear in the present Wikipedia posting of the U-2. Verification of this item would be appreciated.
It's wide range of flammability limits 4-75% and the small amount of energy it takes to get ignition makes it unusual.
http://en.wikipedia.org/wiki/Flammability_limit
I'm interested in hearing and seeing more about his experiment.
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smuv
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Chloroform burns, maybe it can't sustain combustion under most conditions, but it surely will burn.
Again, it is well known that chlorocarbons burn with a blue/green flame, just as alkyl nitrates and nitrites burn with a white flame and alkyl borates
with a green flame.
see
http://books.google.com/books?id=qaOEAAAAIAAJ&pg=PA117&a...
and
http://www.sciencemadness.org/talk/viewthread.php?tid=10758#...
One thing I will say though is that, the green flame probably comes from excited state emission of HCl formed in the combustion of chlorocarbons.
Burning a chlorocarbon, especially as hydrogen poor as CHCl3, in a hydrogen atmosphere will probably result in more intense flame coloration.
[Edited on 6-20-2010 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Mr. Wizard
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Well smuv, you convinced me. I've never seen single chlorine hydrocarbons burn, and the picture is very dramatic. Most of the stuff I've seen burning
was more chlorine saturated, and burned with more very black smoke. especially the unsaturated compounds.
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Picric-A
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I tryed this reaction again with chloform, dichloromethane and carbon tet and got the same results with the chloroform as before. The dichloromethane
burned with a smokey flame as smuv recorded and the carbon tet simply extinguished the flame as i expected (it was once used as a fire extinguisher).
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smuv
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Here is a video of trying to capture the flame color of EtCl. As you can see it is hard to find the right conditions where the brilliant flame color
is visible.
Just heads up some trials were condensed ethyl chloride on a glass slide, and others in a chilled test tube.
EtCl vid (do save link target, it only streams part of the video in the browser before it prematurely stops if you don't)
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Picric-A
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Nice video, did you take that smuv?
The flame i noticed is definintly not as green as seen in that, more blueish, like lead salts...
im not thinking trace transition metals in the glass producing the colouration?
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smuv
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Yeah its mine. The picture in that EtCl thread (linked above) showing the flame color was just taken from one of the frames of that video.
If anything, the coloration from the glass would mostly be sodium ions which would make the flame more yellow. I think this is part of the reason why
on the glass slide it was hard to see the true flame color.
Why don't you try an experiment with a 50% solution of CH2Cl2 in ether? Heat the solution in a test tube with your finger over the opening and
release it into a flame when you feel positive pressure has built up (similar to my experiment). I am confident you will observe a similarly colored
flame as I did with ethyl chloride. Of course exercise caution here.
Edit: If that works like the EtCl experiment, a really interesting experiment would be burning a solution of HCl in some flammable solvent (say
ethanol or ether). If the flame coloration is the same, it can be pretty decisively concluded that we are viewing some excited state emission of HCl
(which I had only previously speculated).
[Edited on 6-20-2010 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Picric-A
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I will try this burning in ether trick and see if i get similar results.
I have however tryed burning HCl dissolved in ether and i simply got incomplete burning of the ether and white fumes given off, presumably the HCl
being released.
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numos
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Quick question, I know chloroform doesn't burn, but wanting to see its reaction to fire, I put a few drops on a concrete slab and hit it with a
blowtorch, it gave off an orange flame and dense black smoke. When the torch was removed, both stopped.
What are the decomp. products for chloroform? The black smoke smelled like a pungent chloriny smell, but it wasn't even close to chlorine itself. Was
there phosgene in that mix of smoke? Phosgene is odorless, but is a possible product?
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BromicAcid
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Yes, likely contained among your products was phosgene. However you are dead wrong if you think phosgene is odorless. Very pungent odor sharp,
stronger than acetone, sweet like DCM. The literature describes it as musty hay or freshly cut grass or green corn.
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chemrox
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This is certainly entertaining and possibly interesting but NOT organic chemistry. Just because an organic compound is involved in an inorganic
experiment does not reach organic chemistry. Where was Nicodem?
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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DraconicAcid
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Quote: Originally posted by BromicAcid  |
Yes, likely contained among your products was phosgene. However you are dead wrong if you think phosgene is odorless. Very pungent odor sharp,
stronger than acetone, sweet like DCM. The literature describes it as musty hay or freshly cut grass or green corn. |
I have smelled it- it struck me as the rancid odour of the bottom of someone's lawnmower before I realized what it was.
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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aga
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| Quote: Originally posted by chemrox | | Just because an organic compound is involved in an inorganic experiment does not reach organic chemistry. |
I'm a total noob, starting chemistry at about the same time as my registration date, see left.
Seems to me that Inorganics are used rather extensively in OC.
e.g. Acetone Peroxide.
Is the H2O2 reactant not Inorganic ?
There has been a reasonable amount of OC involved here, so i fail to see why the Law of OC Purity has been raised twice in this thread.
If i have missed something Major, please U2U rather than reply to this post, so as to prevent the thread being further polluted with uninformative
posts, such as this one.
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