When detergents burn
July 27, 2013 5:32 AM Subscribe
If a detergent such as sodium lauryl sulfate burned (say it was a additive to gunpowder) what does it become? Does it stay as sodium lauryl sulfate, or does it change into something else?
Response by poster: At what concentrations would the sulfur trioxide, and sodium hydroxide be? Will it be at high enough concentration to cause skin irritation and respiratory problems if breathed in small amounts such as the smoke from a gunshot?
posted by john123357 at 6:09 AM on July 27, 2013
posted by john123357 at 6:09 AM on July 27, 2013
If you're cutting black powder with laundry detergent for propellant research purposes, don't forget that gunpowder's ~10% sulfur by weight. You'll already have quite a bit of sulfur trioxide in the smoke.
(having, uh, been a bit of a firebug in my teens, I can neither confirm nor deny that the main problems with burning detergent are: a) the tarry residue, and b) the awful sickly-sweet smell of the perfume going up. Allegedly.)
posted by scruss at 6:47 AM on July 27, 2013 [1 favorite]
(having, uh, been a bit of a firebug in my teens, I can neither confirm nor deny that the main problems with burning detergent are: a) the tarry residue, and b) the awful sickly-sweet smell of the perfume going up. Allegedly.)
posted by scruss at 6:47 AM on July 27, 2013 [1 favorite]
At what concentrations would the sulfur trioxide, and sodium hydroxide be? Will it be at high enough concentration to cause skin irritation and respiratory problems if breathed in small amounts such as the smoke from a gunshot?
That would depend entirely on how much of it you intend to burn and how well-ventilated the area around it might be.
posted by Johnny Assay at 6:48 AM on July 27, 2013
That would depend entirely on how much of it you intend to burn and how well-ventilated the area around it might be.
posted by Johnny Assay at 6:48 AM on July 27, 2013
Much of this depends on how much oxygen is available. If it's mixed with sufficient quantities of a good oxygen donor (i.e. perchlorate or nitrate) you could get very clean combustion.
But if there isn't enough oxygen, then the carbon wouldn't completely burn, and you'd get a lot of soot (elemental carbon).
posted by Chocolate Pickle at 7:04 AM on July 27, 2013
But if there isn't enough oxygen, then the carbon wouldn't completely burn, and you'd get a lot of soot (elemental carbon).
posted by Chocolate Pickle at 7:04 AM on July 27, 2013
If you're concerned about safety, keep in mind that we have evolved to be able to smell sulfur trioxide, and if it approaches anything like a dangerous level, it's going to really reek and the smell will drive you away.
posted by Chocolate Pickle at 7:36 AM on July 27, 2013 [1 favorite]
posted by Chocolate Pickle at 7:36 AM on July 27, 2013 [1 favorite]
Rotten eggs.
posted by Chocolate Pickle at 8:45 AM on July 27, 2013
posted by Chocolate Pickle at 8:45 AM on July 27, 2013
Response by poster: I should also note that what I am talking about is not blackpowder but smokeless powder will the nitrocellulose affect how to the sodium lauryl sulfate burns, or what it becomes?
posted by john123357 at 8:49 AM on July 27, 2013
posted by john123357 at 8:49 AM on July 27, 2013
It really depends on the proportions. Nitrocellulose isn't a net oxygen donor, so the soap would rely on atmospheric oxygen to burn and wouldn't burn very well. You'd get a lot of smoke.
What the heck are you trying to do, anyway?
posted by Chocolate Pickle at 8:54 AM on July 27, 2013
What the heck are you trying to do, anyway?
posted by Chocolate Pickle at 8:54 AM on July 27, 2013
What the heck are you trying to do, anyway?
posted by Chocolate Pickle
Write mystery story where the detective figures out what happened by smelling the residue (that's my best guess). I've got a bunch of junk smokeless powder that I could try an experiment on if you like. I'm not sure I have any powdered SDS on hand though (we use liquid detergent).
posted by 445supermag at 9:25 AM on July 27, 2013
posted by Chocolate Pickle
Write mystery story where the detective figures out what happened by smelling the residue (that's my best guess). I've got a bunch of junk smokeless powder that I could try an experiment on if you like. I'm not sure I have any powdered SDS on hand though (we use liquid detergent).
posted by 445supermag at 9:25 AM on July 27, 2013
No one would do that in a real murder. Adding soap to the powder in a cartridge would have no benefit, and might well prevent the round from firing.
posted by Chocolate Pickle at 9:35 AM on July 27, 2013
posted by Chocolate Pickle at 9:35 AM on July 27, 2013
Response by poster: what does Nitrocellulose break down into when burned?
posted by john123357 at 11:36 AM on July 27, 2013
posted by john123357 at 11:36 AM on July 27, 2013
Nitrocellulose yields carbon dioxide, water vapor, and nitrogen gas. It contains enough oxygen to burn cleanly so it doesn't rely on atmospheric oxygen, which is why it doesn't produce any smoke (hence the name "smokeless powder").
posted by Chocolate Pickle at 12:28 PM on July 27, 2013
posted by Chocolate Pickle at 12:28 PM on July 27, 2013
Response by poster: If the Nitrocellulose is old and starts to break down into nitric acid what does it form when burned?
posted by john123357 at 12:46 PM on July 27, 2013
posted by john123357 at 12:46 PM on July 27, 2013
Same thing.
posted by Chocolate Pickle at 1:11 PM on July 27, 2013
posted by Chocolate Pickle at 1:11 PM on July 27, 2013
Response by poster: so nitric acid itself when burned what does that breakdown into?
posted by john123357 at 2:02 PM on July 27, 2013
posted by john123357 at 2:02 PM on July 27, 2013
Nitric acid is not flammable, it is already oxidised as much as it's likely to get.
Btw, the oxidation/combustion of sulfur compounds does not generally terminate in sulfur TRIoxide, but in sulfur DIoxide. SO3 and SO2 do not smell of rotten eggs, they have a choking odor that catches the back of your throat.
posted by wilko at 2:12 PM on July 27, 2013
Btw, the oxidation/combustion of sulfur compounds does not generally terminate in sulfur TRIoxide, but in sulfur DIoxide. SO3 and SO2 do not smell of rotten eggs, they have a choking odor that catches the back of your throat.
posted by wilko at 2:12 PM on July 27, 2013
Response by poster: If nitric acid was poured on some cotton cloth and then ignited what would it break down into?
posted by john123357 at 8:31 AM on July 28, 2013
posted by john123357 at 8:31 AM on July 28, 2013
Acids don't act like you think an acid acts unless they're mixed with water. Pure acid doesn't burn or chemically alter things. Pure nitric acid poured on cotton cloth wouldn't cause any chemical change.
If it was ignited it would burn very furiously, producing carbon dioxide, water vapor, nitrogen gas, and probably soot (smoke).
Nitric acid solution doesn't actually attack cellulose very effectively. The process of producing gun cotton requires sulphuric acid, too, which acts as a catalyst. (Which means that it assists the process but isn't consumed.)
As long as gun cotton is wet (water is present) it won't burn.
Combustion, in general, requires a fuel and an oxidizer. Often the oxidizer is the atmosphere. Sometimes the oxidizer has been chemically introduced. In many cases the fuel and oxidizer are mixed together. Here are some examples:
Wood fire: wood is the fuel. The oxidizer is oxygen from the air.
The Space Shuttle main engine: the fuel was liquid hydrogen. The oxidizer was liquid oxygen.
Space Shuttle solid rocket boosters: the fuel was small quantities of hydrocarbon and binder. The oxidizer was ammonium perchlorate.
Smokeless Powder: nitrocellulose is both fuel and oxidizer. If properly manufactured, sufficient nitrate is added to the cellulose to provide exactly as much oxygen as is needed for perfect combustion.
ME-163 Komet -- was a rocket plane used by the Germans in WWII. It used "C-Stoff" and "T-Stoff". C-Stoff fuel was a mix of Methanol and Hydrazine. T-Stoff oxidizer was high concentration hydrogen peroxide.
Pure nitric acid has been used as an oxidizer but not very often because it's such nasty stuff. Cotton is mainly cellulose, which is a polymer of the sugar Glucose, which is mainly made of carbon and hydrogen (though there's some oxygen in it, too). So your conjectural mix of pure nitric acid and cotton succeeds in having both fuel and oxydizer, and would burn like mad.
However, if it was nitric acid in water (say, 15% or 20%) poured on cotton, the water would dominate and prevent any burning.
posted by Chocolate Pickle at 9:47 AM on July 28, 2013
If it was ignited it would burn very furiously, producing carbon dioxide, water vapor, nitrogen gas, and probably soot (smoke).
Nitric acid solution doesn't actually attack cellulose very effectively. The process of producing gun cotton requires sulphuric acid, too, which acts as a catalyst. (Which means that it assists the process but isn't consumed.)
As long as gun cotton is wet (water is present) it won't burn.
Combustion, in general, requires a fuel and an oxidizer. Often the oxidizer is the atmosphere. Sometimes the oxidizer has been chemically introduced. In many cases the fuel and oxidizer are mixed together. Here are some examples:
Wood fire: wood is the fuel. The oxidizer is oxygen from the air.
The Space Shuttle main engine: the fuel was liquid hydrogen. The oxidizer was liquid oxygen.
Space Shuttle solid rocket boosters: the fuel was small quantities of hydrocarbon and binder. The oxidizer was ammonium perchlorate.
Smokeless Powder: nitrocellulose is both fuel and oxidizer. If properly manufactured, sufficient nitrate is added to the cellulose to provide exactly as much oxygen as is needed for perfect combustion.
ME-163 Komet -- was a rocket plane used by the Germans in WWII. It used "C-Stoff" and "T-Stoff". C-Stoff fuel was a mix of Methanol and Hydrazine. T-Stoff oxidizer was high concentration hydrogen peroxide.
Pure nitric acid has been used as an oxidizer but not very often because it's such nasty stuff. Cotton is mainly cellulose, which is a polymer of the sugar Glucose, which is mainly made of carbon and hydrogen (though there's some oxygen in it, too). So your conjectural mix of pure nitric acid and cotton succeeds in having both fuel and oxydizer, and would burn like mad.
However, if it was nitric acid in water (say, 15% or 20%) poured on cotton, the water would dominate and prevent any burning.
posted by Chocolate Pickle at 9:47 AM on July 28, 2013
Generally it isn't too difficult to figure out the combustion products if you assume complete combustion, just by looking at the chemical formulas for the source materials:
Hydrogen will combine with oxygen to become water vapor.
Carbon will combine with oxygen to become carbon dioxide.
Nitrogen prefers its own company and will become N2.
Phosphorus will combine with oxygen to become phosphate.
Sulfur will combine with oxygen to become Sulfur Dioxide (thanks, Wilko)
Metals generally oxydize, too, though alkalis often become hydroxides instead.
There isn't anything mystical about this, and there certainly isn't any alchemistry going on.
When there isn't sufficient oxygen, then things start getting tricky. Carbon, for instance, may become carbon monoxide, or it might convert to fullerenes (which turns out to be what most soot is made of, though that was only discovered recently).
And there are a few particularly tricky mixes which yield other things. Thermite, for instance produces lots of strange things but in particular it produces iron metal, unoxydized.
But those kinds of things are exceptions. Most organic stuff, when burned, produce carbon dioxide, water vapor, nitrogen gas, and maybe phosphate and/or sulfur dioxide.
posted by Chocolate Pickle at 10:00 AM on July 28, 2013 [1 favorite]
Hydrogen will combine with oxygen to become water vapor.
Carbon will combine with oxygen to become carbon dioxide.
Nitrogen prefers its own company and will become N2.
Phosphorus will combine with oxygen to become phosphate.
Sulfur will combine with oxygen to become Sulfur Dioxide (thanks, Wilko)
Metals generally oxydize, too, though alkalis often become hydroxides instead.
There isn't anything mystical about this, and there certainly isn't any alchemistry going on.
When there isn't sufficient oxygen, then things start getting tricky. Carbon, for instance, may become carbon monoxide, or it might convert to fullerenes (which turns out to be what most soot is made of, though that was only discovered recently).
And there are a few particularly tricky mixes which yield other things. Thermite, for instance produces lots of strange things but in particular it produces iron metal, unoxydized.
But those kinds of things are exceptions. Most organic stuff, when burned, produce carbon dioxide, water vapor, nitrogen gas, and maybe phosphate and/or sulfur dioxide.
posted by Chocolate Pickle at 10:00 AM on July 28, 2013 [1 favorite]
Response by poster: So if sulfuric acid (perhaps with the help of a oxidizer like nitrate) is poured on cotton and ignited what are the combustion products?
posted by john123357 at 11:00 AM on July 28, 2013
posted by john123357 at 11:00 AM on July 28, 2013
It wouldn't ignite as long as it was wet.
posted by Chocolate Pickle at 11:31 AM on July 28, 2013
posted by Chocolate Pickle at 11:31 AM on July 28, 2013
Response by poster: What if it was low water acid and had a high amount of ammonium nitrate in it?
posted by john123357 at 3:30 PM on July 28, 2013
posted by john123357 at 3:30 PM on July 28, 2013
I think you need to go find a college chemistry grad student and spend an evening buying him beer.
posted by Chocolate Pickle at 5:34 PM on July 28, 2013 [3 favorites]
posted by Chocolate Pickle at 5:34 PM on July 28, 2013 [3 favorites]
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posted by Chocolate Pickle at 5:58 AM on July 27, 2013