Combustible gas with no oxygen?

[Forensicmad]

Hi,

This is my first time posting so... hi

Anyway, I have a question (which you may have guessed).

 

I am writing a book/story which is about life on another planet and i am trying to keep it as scientifically accurate as possible. One thing which i need to know is;

Is there any gas which is combustible in an atmosphere with no oxygen?

Or even any substance?

I'm pretty sure you will all say that all combustion is, is the rather hot, oxidising reaction which we see as a flame. My question is really asking however, if there was an atmosphere with no conventional earthly fire, could something at least resemble it or would i have to create something? I have to stay away from oxygen as much in its elemental form because it would conflict with far too much else in the story.

 

Thanks very much

Matt, 16

[RyanJ]

Welcome to SFN!

 

Yes there are such chemicals when you consider combustion as oxidation.

 

Lets take an example, if we were to burn hydrogen in an oxygen atmosphere the 2 hydrogens each "donate" 1 electron to the oxygen atom - they have lost electrons and have therefor been oxidised. The reverse if true for oxygen which has been reduced.

 

So the answer is a simply yes - elements that are very electronegative will allow you to "burn" or oxidise things. Examples could be fluorine and chlorine for example

 

Good luck with your book!

 

Ryan Jones

[Forensicmad]

Thank you very much for the quick reply. I finally have an answer i've looked so long for. Funny isn't it?

Hours of trawling the internet comes up with nothing and then just 10 minutes waiting for your reply gives me one. Sods law.

[RyanJ]

Thank you very much for the quick reply. I finally have an answer i've looked so long for. Funny isn't it?

Hours of trawling the internet comes up with nothing and then just 10 minutes waiting for your reply gives me one. Sods law.

 

Indeed - always the same, it will also be interesting to see a book about a planet that has chlorine and or fluorine in the atomosphere. Not somewhere I'd like to live

 

Cheers,

 

Ryan Jones

[Forensicmad]

So far, I have researched a lot and come up with a fair amount. The theory behind the whole plot is immense. I have so far decided on the respiration of the inhabitants which involves methane, ethane, an organic liquid compound and an equivalent to glucose. The symbolic reaction suprisingly works and so in theory, does work.

I have actually already looked into fluorine and chlorine. I have determined that at the temperature the planet is, chlorine would be in its solid state and I am advised that fluorine is not too responsible to have in the atmosphere in large amounts. Anyway, thanks.

 

Hmm... I don't remember putting this in the homework section. It was supposed to be under the chemistry section. Oh well.

[Bignose]

Chemicals like ethers, with -O-O-'s in the middle of their structures, or chemicals with even more -O-'s (like -O-O-O- or more) will degrade and generate its own oxygen which can then be be used for combustion. I know of at least one horror story of some poor student heating up a beaker full of old ether that exploded on him. Maybe not exactly what you wanted, but a different answer to the 1st question.

[RyanJ]

Chemicals like ethers, with -O-O-'s in the middle of their structures, or chemicals with even more -O-'s (like -O-O-O- or more) will degrade and generate its own oxygen which can then be be used for combustion. I know of at least one horror story of some poor student heating up a beaker full of old ether that exploded on him. Maybe not exactly what you wanted, but a different answer to the 1st question.

 

Yes but those are not much good as they would be quite solid long before chlorine would

 

@Forensicmad: There are others, here are a few I can think of:

 

• Nitric oxide ([ce]NO[/ce])
  
• Nitrogen dioxide ([ce]NO2[/ce])
  
• Ozone ([ce]O3[/ce])
  

 

Thats all I have off the top of my head.

 

Cheers,

 

Ryan Jones

[YT2095]

actualy, it doesn`t matter which way around you have the oxidiser or reducer in the atmosphere.

an atmosphere of pure methane or hydrogen will still support a flame, only it would apear as the Oxygen or Fluorine or Chlorine is burning instead

the atmosphere need not be the Oxidiser.

[Forensicmad]

Wow, thank you very much for all the info.

I must say however, that it is a little overwhelming for me. I even showed it to my chemistry teacher and she didn't understand some of it either.

 

Would you know of any simpler explanations (please)?

 

If this continues to evade me, I probably will make up my own version of fire using different materials and effects - should prove interesting.

 

Anyway, thanks for all the effort you have put in so far; at least I know that it can potentially be done.

[RyanJ]

Wow' date=' thank you very much for all the info.

I must say however, that it is a little overwhelming for me. I even showed it to my chemistry teacher and she didn't understand some of it either.

 

Would you know of any simpler explanations (please)?

 

If this continues to evade me, I probably will make up my own version of fire using different materials and effects - should prove interesting.

 

Anyway, thanks for all the effort you have put in so far; at least I know that it can potentially be done.[/quote']

 

I believe what YT said simply was that an atmosphere of methane or hydrogen could support "combustion" in terms of oxidation

 

Cheers,

 

Ryan Jones

[YT2095]

in a nutshell, a fire as you describe, needs 3 parts (2 parts if you discount Heat).

 

you need a Reducer and an Oxidiser, and then Trigger energy to make them react (like we use Matches here to provide the heat to start paper burning etc...)

 

 

Here we have Oxygen in our air, that`s our Oxidiser, and Methane or butane or paper etc.. as the reducers.

 

now then, if the air was pure methane or butane, and you lit a match very little to nothing would happen, it would NOT blow up the planet or set the world on fire. You cannot set alight pure methane or hydrogen alone.

it Needs and oxidiser.

 

and so, in such a methane atmosphere, you`de set fire to Chlorine or Oxygen instead, even if the Chlorine was frozen solid (like wood or paper or candle wax) it would still burn if you heated it with a suitable "Match".

 

although I suspect your planet has alot more Gravity than here on Earth as methane is quite a Light gas, and would get lost into space easily.

[Forensicmad]

Thanks very much. That makes a lot more sense

Yes, I have already looked into the gravity aspect and have an idea of what the atmospheric pressure would be with methane and ethane. I have a much better idea what to look for now; thanks.

[RyanJ]

Thanks very much. That makes a lot more sense

Yes' date=' I have already looked into the gravity aspect and have an idea of what the atmospheric pressure would be with methane and ethane. I have a much better idea what to look for now; thanks.[/quote']

 

Sounds like a nice place - add some ethyne in there too, its pretty reactive and would make things interesting to say the least

 

Maybe you should look ito the composition of the gas giants atmospheres for reference, very alien, very toxic and very intersting!

 

Cheers,

 

Ryan Jones

[YT2095]

well oddly enough, Mars, even with a mostly CO2 atmos, Magnesium metal will still burn in it!

 

Magnesium is a good reducer in that respect.

[Forensicmad]

Yeah, sounds fun. I think I will add Ethyne (Acetylene), along with Phosphine (Jupiter has it) into the atmosphere. It is starting to get interesting - I was having a hard time finding such gases which are in fact gases at the temperature I want.

[YT2095]

well make sure you don`t go TOO overboard with them as many may naturaly react with each other making the composition not at all possible, and if you want Reality (so to speak) don`t just bang a whole load of stuff together because it sounds good, you still have to be carefull with Reducers, some reduce better than others, making the lesser reducers potentialy Oxidisers by comparison

it`s all relative (to coin a Physics phrase).

[Forensicmad]

Yeah, that was just a little bit of fun. I am trying to make everything coincide with everything else so that it can't be found to blow up if it was enacted here on Earth. I want something that scientists could look at and think maybe this is possible - I want to make them see the diversity (preferebly one that works)

[RyanJ]

Hmm.. something like the setup of Jupiter and the other outer planets would be interesting.

 

Jupiter:

• Hydrogen
  
• Helium
  
• Methane
  
• Water vapour
  
• Ammonia
  
• Carbon
  
• Ethane
  
• Hydrogen sulphide
  
• Neon
  
• Oxygen
  
• Phosphine
  
• Sulphur
  
• Ammonia.
  

 

Saturn is pretty much the same as Jupiter.

 

Uranus is a little different:

• Hydrogen
  
• Helium
  
• Methane
  
• Ammonia
  
• Ethane
  
• Acetylene
  
• Carbon monoxide
  
• Hydrogen sulfide
  

 

Neptune is a little different:

• Hydrogen
  
• Helium
  
• Methane
  
• Ethane
  
• Hydrogen Deuteride
  

 

Maybe Venus has some interesting features too:

 

• Carbon dioxide
  
• Nitrogen
  
• Sulfur dioxide
  
• Argon
  
• Water vapor
  
• Carbon monoxide
  
• Helium
  
• Neon
  
• Carbonyl sulfide
  
• Hydrogen chloride
  
• Hydrogen fluoride
  

 

All of which are nasty and would be a good base for some interesting reactions

 

Cheers,

 

Ryan Jones

[Forensicmad]

Wow, thank you very much Ryan for all that info. From what info I already had, it appeared the planet would be a little like Uranus.

 

In reply to YT2095 #11:

You say that if I had a methane atmosphere, it would not blow up. If I placed oxygen or chlorine in however, it would be able to combust. Because I am steering as far away from oxygen as possible and it is too cold for the gaseous state of chlorine (it is in its liquid state), would there be any way for it to linger in the atmosphere? I know that water 'evaporates' from the sea due to a simple diffusion gradient - the air is unsaturated or something. Would this work with chlorine? Would chlorine be able to stay in the air or atmosphere in a liquid state?

 

(If so, it would probably add a greenish hue to the air but something strange like that is to be expected of an extra terrestrial planet)

[RyanJ]

 

In reply to YT2095 #11:

You say that if I had a methane atmosphere' date=' it would not blow up. If I placed oxygen or chlorine in however, it would be able to combust. Because I am steering as far away from oxygen as possible and it is too cold for the gaseous state of chlorine (it is in its liquid state), would there be any way for it to linger in the atmosphere? I know that water 'evaporates' from the sea due to a simple diffusion gradient - the air is unsaturated or something. Would this work with chlorine? Would chlorine be able to stay in the air or atmosphere in a liquid state?[/quote']

 

It will work yes. Even though the giant planets have frozen ammonia in them they are also known to have gaseous ammonia in their outer layers. You could attribute this to strong solar radiation or have another large planet nearby then you could have an effect like that of Io, a squeesing effect that generates some heat.

 

Either way it should still be possible for you to have some chlorine loose in the atmosphere

 

As for the information posted, I would have posted the complete table but it rather large so I decided to shorten it a tad

 

Cheers,

 

Ryan Jones

[Forensicmad]

EXCELLENT! Thank you very much all.

I am just finalising the composition and it so far contains Methane, Ethane, of course, Chlorine are all certainly included.

I was having a quick look at Wikipedia for Acetylene and under "Safety and handling" in "Toxic effects", it says:

It may also contain toxic impurities: the Compressed Gas Association Commodity Specification for acetylene has established a grading system for identifying and quantifying phosphine, arsine, and hydrogen sulfide content in commercial grades of acetylene in order to limit exposure to these impurities.

Does this mean that Phosphine and Acetylene go together well, or badly?

 

The other gases include:

Argon (nearly all the planets in our solar system have it)

Maybe Nitrogen to make up the difference (it is inert so shouldn't it be okay?)

Finally, Phosphine and Acetylene if they go together. If not, I will pick one.

 

Thanks, just one more thing to clear up and that will be it.

Otherwise, thank you very much for all your help.

[RyanJ]

Does this mean that Phosphine and Acetylene go together well' date=' or badly?

[/quote']

 

That means that commercial Acetylene may contain it so they should work together with little or no problems

 

The composition looks quite interesting and also belivable which is good. The high solar radiation from the sun will make some interesting reactions in the upper atmosphere I think.

 

You should also include some hydrogen and helium in the atmosphere as they are the most abundant elements in the universe after all

 

Cheers,

 

Ryan Jones

[YT2095]

I`de be Very circumspect about introducing Phosphine!

[Forensicmad]

Why? Is it dangerous? Toxic? Very volatile?

Would you just recommend Acetylene?

[RyanJ]

Why? Is it dangerous? Toxic? Very volatile?

Would you just recommend Acetylene?

 

Well, phosphine is highly flammable and very toxic but it does exist in the outer giants in small quantities so no problems. Acetylene is also found in the outer planets so again should be fine as long as you don't overload the atmosphere with the stuff

 

Cheers,

 

Ryan Jones