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Saffer
09-06-2009, 06:16 AM
Consider that coal is mostly carbon. When you put it in an oxygen rich environment and apply a little heat, the carbon reacts with the oxygen and gives off more heat and sets off a chain reaction. The carbon and oxygen become carbon dioxide and carbon monoxide (any others?).
Graphite is, from what I understand, sheets of carbon and diamond is carbon arranged in little cubes and neither, to my knowledge is flammable.
What if I put both in a high pressure, pure oxygen chamber and applied some sort of extreme heat to them. Can I get either the graphite or the diamond to ignite and continue to burn on its own?

engineer_comp_geek
09-06-2009, 06:19 AM
Yup. That's how they figured out diamonds were carbon originally.

Heat the diamond with a blowtorch and drop it in liquid oxygen and it will burn on its own, no problem.

RealityChuck
09-06-2009, 02:30 PM
Yes. Diamonds can burn, though they have a high ignition point.

friedo
09-06-2009, 02:34 PM
Ask and ye shall receive (http://www.youtube.com/watch?v=3mKqtT8J2ms).

Chronos
09-06-2009, 03:00 PM
Graphite is, from what I understand, sheets of carbon and diamond is carbon arranged in little cubes and neither, to my knowledge is flammable.Isn't the carbon in coal mostly in the form of graphite?

Sigene
09-06-2009, 03:20 PM
accidently and without the liquid oxygen. I was trying to clean a diamond film that had some contamination on it. I tried everything and couldn't get it to clean up. So I had the bright idea of burning the contamination off.....when I was done the contamination and diamond film was gone.

I'm always amazed how many time my experience with diamond is relevant here. Every few months someone is asking about it in some way.

enipla
09-06-2009, 03:39 PM
Ask and ye shall receive (http://www.youtube.com/watch?v=3mKqtT8J2ms).Wow. What and interesting question, and interesting link. I had no idea. Never thought of it really.

And I thought that lighting cigars with hundred dollar bills was expensive. Diamonds in champagne glasses full of liquid oxygen. Now that's a candle.

johnpost
09-06-2009, 04:03 PM
Isn't the carbon in coal mostly in the form of graphite?

graphite is the highest grade coal though doesn't burn well. fuel coals are lower grades of anthracite, bituminous and lignite.

wolf_meister
09-06-2009, 04:13 PM
... and let's not forget that the first person to burn a diamond (intentionally or otherwise) was Antoine Lavoisier, back in the eighteenth century.

Yossarian
09-08-2009, 09:29 AM
graphite is the highest grade coal though doesn't burn well.

No, no, no!

Graphite is not coal. Coal has no graphite.

Diamond and Graphite both have a crystalline structure. In diamond, each carbon atom is coordianted by four others (tetrahedral coordination), which manifests itself macroscopically as an isometric crystal usually in a cubic or octahedral form. In graphite, each carbon atom is coordinated by three others (triangular coordination), which results in hexagonal crystals that form "sheets" which are weakly bonded to other "sheets".

Coal may be mostly carbon, but it is not crystalline and contains no graphite. Graphite is not coal, much less the "highest grade". (I'm not very well versed in organic geochemistry, so I can't tell you exactly what it is without looking it up, but I know what it ain't!)

Ludovic
09-08-2009, 09:34 AM
"Diamonds are until they get heated up and dropped into liquid oxygen."

CalMeacham
09-08-2009, 09:37 AM
Yossarian says:

No, no, no!

Graphite is not coal. Coal has no graphite.




According to Wikipedia, coal can contain graphite:

Types of coal
Believed approximate position of the proto-continents toward the end of the Carboniferous period; the light blue represents shallow seas where many of today's coal deposits are found, as opposed to deeper waters which gave rise to oil bearing rocks derived from marine species. The ice caps were known to be very large, lowering sea levels extensively by locking up oceanic waters into solid ice, though how large the ice caps became is a matter of debate. The position of most continental foundations in lower latitudes definitely created a series of successive shallow swamplike seas we burn for today's coal sourced electricity.

As geological processes apply pressure to dead biotic matter over time, under suitable conditions it is transformed successively into

* Peat, considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland.
* Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age.
* Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.
* Bituminous coal, dense mineral, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.
* Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil, as from the deposits in Pennsylvania.
* Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.



http://en.wikipedia.org/wiki/Coal


Graphite may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite, although it is not normally used as fuel because it is hard to ignite.

http://en.wikipedia.org/wiki/Graphite

BrotherCadfael
09-08-2009, 10:41 AM
If I recall correctly, physicist Phillip Morrison had a PBS special some years back, and he got Julia Childs (it was quite a few years back) to cook a diamond to ashes. So, yes, they will burn.

Yossarian
09-08-2009, 10:44 AM
Well, if Wikipedia says so, who am I to argue?

Whack-a-Mole
09-08-2009, 11:41 AM
I was under the impression pretty much everything can burn under the right conditions. Even water.

Giles
09-08-2009, 11:46 AM
I was under the impression pretty much everything can burn under the right conditions. Even water.
Burning water would be about as easy as burning carbon dioxide.

CalMeacham
09-08-2009, 11:48 AM
Well, if Wikipedia says so, who am I to argue?

It's not just Wikipedia -- Google "Coal Graphite" and you'll get lots of hits, many from respectable sources equating the two.

Certainly not all coal is graphite (which generally contains lots of much more complex hydrocarbons), but, apparently, in some circles, all graphite is a sort of "limiting case" of coal.


I brought up the Wikipedia page because, oddly enough, I'd been reading it last week, and the bit about graphite being the "pure case" of coal stuck in my mind. It's not because I think Wikipedia is the Ultimate Reference Tool.

Chronos
09-08-2009, 12:00 PM
If I recall correctly, physicist Phillip Morrison had a PBS special some years back, and he got Julia Childs (it was quite a few years back) to cook a diamond to ashes. So, yes, they will burn.You can't burn diamond "to ashes". Ashes are from trace components in whatever you're burning that either don't burn, or burn to a solid. But diamonds are about as pure carbon as you'll ever find, and carbon burns to a gas.

lazybratsche
09-08-2009, 12:15 PM
Burning water would be about as easy as burning carbon dioxide.

True. In both cases, you just need a stronger oxidizer than oxygen. Fluorine does the trick, and will quite energetically replace the oxygen in just about anything. You don't want to be anywhere near when it happens though -- byproducts of fluorine gas and water include HF, which happens to be once of nastier acids.

Of course, once you have your fluorinated combustion products, you've reached the end point, since there's nothing that's even more reactive.

Chronos
09-08-2009, 01:38 PM
If you stretch the definition of "burning" a bit, then you could also oxidize those fluorine compounds further, at the cost of putting in more energy than you're getting back out.

CC
09-08-2009, 01:56 PM
By the way, that link to the Youtube video has an interesting sidebit. I used to show the entire film to my classes and it's a great movie - lots of cool illustrations of many of the elements in addition to an explanation for the periodic table. But in the original movie, when the diamond is heated and dropped into the lox, the music on the sound track was from Diamonds Are Forever. Clearly, someone with a copyright issue got to the producers of the film and had that changed. If you listen, you can hear the sound track stop when the narrator introduces the illustration and some random music shows up to back up the demonstration. When he appears again, the original soundtrack resumes.

BrotherCadfael
09-08-2009, 07:49 PM
You can't burn diamond "to ashes". Ashes are from trace components in whatever you're burning that either don't burn, or burn to a solid. But diamonds are about as pure carbon as you'll ever find, and carbon burns to a gas.Serves me right for not looking it up beforehand. She didn't burn a diamond, she burned an elegant meal to black masses of carbon, to show that food is mostly carbon, like the diamond he burned in another segment.

The video of Julia's segment is here (http://www.youtube.com/watch?v=iw-cZhTISBk).