phlogiston
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An oxygen flame in a reducing environment
I'm sure many of you have read about Saturn's moon Titan and the fantastic data that the NASA/ESA/ASI Cassini/Huygens mission has yielded (and it is
still continuing to do so).
The atmosphere of titan is composed of nitrogen (98.4%), methane (1.4%) and hydrogen (0.1-0.2%). This got me thinking on whether it would be possible
to light a flame of oxygen in a hydrocarbon atmosphere.
Here on earth, you can light a flame of a hydrocarbon gas and the air provides the oxygen. Imagine the reverse: a nozzle expelling oxygen gas in an
atmosphere containing a high concentration of hydrocarbons. Would it be possible to light a similar flame?
I can't find any literature on this subject and am not able to actually try this in the immediate future. Any insight or references that can satisfy
my curiosity?
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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bfesser
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Oh, boy, that's going to require some complex thermodynamics and fluid dynamics that's well beyond my understanding. Interesting thoughts, though.
Now <em>I'm</em> curious!
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bismuthate
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This is a very intresting question. I have always wondered about "backwards" if you will reactions such as dropping a piece of ice in molten
potassium. I believe that it would work because the O2 can still react with the methane. This would make for a very cool experiment.
(sorry I have no reference only a hunch and curiosity)
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plante1999
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I remember reading a lecture experiment book where there was a section about combustion. They used what they called combustion tube with two stopper,
the botom one had two hole and tow one had one. They passed the reducing gas at the top, and oxidizing gas at the bottom, and used the third tube to
analyse the product. They burned oxygen in hydrogen, oxygen in methane to make acetylene (and copper acetylide), and many others.
Apparently it look like a regular flame.
I never asked for this.
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ScienceSquirrel
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I suspect that it would work but not in an atmosphere like Titan's.
Too much nitrogen and not enough flammable gases.
[Edited on 14-10-2013 by ScienceSquirrel]
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Oscilllator
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Quote: Originally posted by bfesser  | | Oh, boy, that's going to require some complex thermodynamics and fluid dynamics that's well beyond my understanding. Interesting thoughts, though.
Now <em>I'm</em> curious! |
Nope! It requires a big cylinder of methane, an airtight room, a cylinder of oxygen, a sparker and some serious balls.
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Endimion17
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Of course it can (not the Titan thing - its atmosphere is almost pure nitrogen).
The almost universal thinking that flames can't be produced by "reverse situation" is "because it is an oxidizer and not a fuel". It is the dumbed
down school model used as universal truth. A common school problem.
Methane and oxygen are reacting. One gives electrons, another receives them. That has nothing to do with the flame dynamics. Those are two fuels and
that's it. The fact one is an oxidizer and one is a reducer has meaning when you get down to the level of electron cloud shifting.
It's only the fact we're living in an oxygen atmosphere and have reducers around (mostly organic stuff) that we think that only reducers can give a
flame in an oxidizer. Completely untrue and it's a terrible shame kids are taught these things. If we were living in a reducing environment and we had
oxidizing compounds around, there would still be flames.
I understand that youngsters need a simple model to understand the fire hazard, but older students should be able to understand there's no difference.
If fluorine's chemistry was more energetic, it would burn in air no matter air would be a reducer.
[Edited on 15-10-2013 by Endimion17]
[Edited on 15-10-2013 by Endimion17]
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bismuthate
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that would be horrifying (yet amazing).
I believe we could introduce a small steam of chlorine into acetyline to produce rather spectacular results. That would most definitly react at room
temperature so maybe somebody (possibly me) could perfom that experiment as an example of a oxidizer burning in a recucing atmosphere.
Here is a link to a video (many will be familiar with) that includes chlorine and acyetyline reacting.
http://www.youtube.com/watch?v=UWYiyFkfxQU
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woelen
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I have done a similar experiment with passing chlorine gas into PH3. This does burn in PH3. I had the PH3 in an upside down test tube, immersed in
water. When Cl2 is passed in this tube (from below), then it ignites in the PH3 and the volume of gas decreases (the products of combustion, PCl3,
PCl5, and HCl, dissolve in the water).
This experiment is combustion of an oxidizer in a reducing atmosphere. The use of Cl2 as oxidizer is easier than the use of O2 as oxidizer, because
the Cl2 ignites at room temperature, so no sparker is needed to ignite the gas.
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bismuthate
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I saw that in the video it was very interesting however I can't use phosphine at the time. The acetyline method would be better for me personaly.
To everyone who helped make that video it was amazing. Great job!
SM should try making another video collabration.
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Eddygp
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Wow good question. I have actually thought about similar things: an oxygen balloon is "immolated" in a pure C2H6 atmosphere 
there may be bugs in gfind
[ˌɛdidʒiˈpiː] IPA pronunciation for my Username |
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Endimion17
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Someone might try to combust oxygen or chlorine in propane, propane-butane or butane. It's a potentially highly dangerous reaction setup. The
container should be completely filled with the reducer. In fact, the reducer should be flowing through it at a very slow rate, to avoid air getting
inside, or to avoid the depletion, or to avoid explosive mixture formation.
I'd recommend propane and chlorine. It's better for the stuff that is introduced into the reducer to be denser because you don't want your oxidizer to
quickly float up.
Also, a system that can deliver a spark (piezoelectric) every few seconds should be used above the tube delivering the oxidizer. Just in case the
flame becomes unstable if the flow drops down, and of course to ignite it in the first place.
I don't know if you can see this video (YouTube, governed by assholes from Google who shove their Google+ crap into users' mouths, started experiencing lots fo problems with
older videos), it's a kind of setup where I tried to burn propane in nitrogen(I) oxide. A modification of the setup could be used here, as well.
The most important thing is to ensure the reducing environment is constant. The best thing is to use a slightly positive pressure and vent everything
outside, away from ignition sources.
Alternatively, but only if oxygen is used, one might introduce the runoff gas into the air intake of a working Bunsen burner.
[Edited on 16-10-2013 by Endimion17]
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woelen
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This sounds like a very dangerous thing to do. A spark, produced every few seconds is not often enough. In a few seconds, quite a lot of the oxidizing
gas may be pushed into the reducing gas and if a spark does not lead to ignition, then the next spark, a few seconds later, may lead to an explosion!
The only safe method of demonstrating this is using a reductor/oxidizer mix, which ignites at room temperature (e.g. PH3 plus Cl2, C2H2 plus Cl2, SiH4
plus O2). Unfortunately, the added safety from the point of view of risk of explosion comes at the cost of using more poisonous reagents. I myself,
however, am more prepared to handle poisonous reagents than the risk of explosion with the possibility that splinters of glass are flying around at
high speed.
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DraconicAcid
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Somewhere, in one of my books, I have directions for setting up an oxygen-in-natural-gas flame. You take a hose from the gas line, attach it to a
funnel, and ignite it so that you have a wide flame at the mouth of the funnel. A thin glass tube with a stream of air coming out is then passed
through the flame into the main part of the funnel, which has a flame coming out of it.
If I find the book, I'll scan it, or at least post a cite.
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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bob800
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I have a digital copy of a Scientific American article about this matter:
"Flames in Which Air Is Introduced into a Flammable Gas Rather Than Vice Versa"
by Jearl Walker
November, 1979
Attachment: flamearticle.pdf (279kB)
This file has been downloaded 770 times
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Endimion17
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| Quote: Originally posted by woelen | This sounds like a very dangerous thing to do. A spark, produced every few seconds is not often enough. In a few seconds, quite a lot of the oxidizing
gas may be pushed into the reducing gas and if a spark does not lead to ignition, then the next spark, a few seconds later, may lead to an explosion!
The only safe method of demonstrating this is using a reductor/oxidizer mix, which ignites at room temperature (e.g. PH3 plus Cl2, C2H2 plus Cl2, SiH4
plus O2). Unfortunately, the added safety from the point of view of risk of explosion comes at the cost of using more poisonous reagents. I myself,
however, am more prepared to handle poisonous reagents than the risk of explosion with the possibility that splinters of glass are flying around at
high speed. |
That's why apparatus needs a buffering system (balloon, for example, if oxygen is used) and valves, to control the rate of gas addition. It can be
done safely. Syringe is very safe because the user controls the addition directly. Making the gases ad hoc, without a buffer, would not be a
smart idea, of course.
One might use an inductor for faster sparks. The delivery tube should be rather narrow, almost a capillary tube.
Here's more material.
http://terpconnect.umd.edu/~pbs/2004-Sunderland-et-al-CNF.pd...
Luminosities are different when diffused flames with hydrocarbon fuels are used. There should not be lots of differences in cases where there is no
soot.
[Edited on 16-10-2013 by Endimion17]
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