tryptic
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Fires from solvents
Assuming I were to reflux a slightly larger quantity of a high boiling solvent (organic chemistry purposes..), like for example DMSO, any idea of how
violently it would explode if the reflux exhaust fumes were to ignite for some reason? (Note that DMSO has a flashpoint of about 89 degrees celsius
however!)
Is it likely that the glass bottle containing the DMSO would actually explode..? If it would, would it explode violently..?
I guess I would have to buy a powder fire extinguisher in any case..
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vulture
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It won't explode unless you're a very unlucky chap and it's mixed in the right proportions with air. This is very unlikely though,
because your apparatus is going to be filled with DMSO vapor.
You'll just have a nice flame where there is air contact, unless that spot happens to be an opening of several inches ofcourse.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Ium
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It is best to purge the apparatus with an inert (or relatively inert) gas beforehand if you are worried about explosions in the first stages of
distillation. Although as vulture said, once distillation proceeds at the normal rate, the apparatus will be filled with solvent vapor in such high
concentration that even if an ignition source was present it would be highly unlikely to sustain combustion to any considerable degree.
Unless of course you are distilling some nasties like Hydrazine, Perchloric Esters and TeNMe . That opens up a whole new world of possible hazards.
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BromicAcid
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Woah lum, perchloric esters, I shudder to think of that.
Just worry about purging the oxygen from your system to prevent the % mixture necessary for explosion from being reached. Those little cans of
'air' for cleaning computer parts can work for this, as can propane or any gas that will not attack your product or spontaneously decompose
on it's own. Helium would not be good as it is too light. Regardless, after the reaction gets going the system will be flooded with your
reaction vapors and an explosion in your system should not be a problem. Your exit gasses though....
Edit: It is always good to have a fire extinguisher around though. 
[Edited on 8/5/2004 by BromicAcid]
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Organikum
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A wet towel and a bucket with sand beat any fire-extiguisher.
Compatibility and cleanup thats all I say.
Solvents are not like US-cars which explode when kicked at the bumper. They usually burn. Just dont panic and have your towel handy thats all it
needs.
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BromicAcid
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Solvents might 'just burn' but if you don't put them out then you can be in trouble. A large sample of benzene that caught on fire
took up enough heat from the fire to flash boil over the container and spread a huge fire everywhere. So just be sure to put them out, don't
take the advice you are given at home about letting an oil fire burn and just let it go (well, go ahead, let oil burn). Careful when smothering
because you can open a container recently smothered and full of hot fumes that can ignite explosively, just cover and leave alone for awhile.
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mick
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DMSO exploding
If you mean dimethyl sulphoxide (DMSO) in organic chemistry, it is non-flammable and will not explode and its melting point is 18 degrees C. The flash
point is how hot it has to be before it can burn, 85 degrees C, it will not catch fire a room temp, most solvents, eg petrol have a flash point below
0 degrees C. The auto-iginition point of DMSO is 215 degrees C and it is not very volatile, so it would be hard work to get enough of the stuff in the
air to catch fire. Ether boils at 35 degrees C, flash point -40 degrees C, auto-ignition temperature of 185 degrees C (can be ignited by a hot plate
or a spark, from experience) and explosive in air down to 2% concentration.
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unionised
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You might thnk DMSO is non flammable, I once set fire to some by accident in the lab. It burned with a blue flame. I put it out with a cover glass
after turning off the heat. No real harm done ( just buggered up the experimental yield).
I have seen a few accidental fires in the lab. They were all small scale and didn't do any harm.
Its auto- ignition temp of DMSO is not far above the boiling point and the vapour is quite dense so it's fairly easy to arrange things so that
the vapour from the boiling liquid drifts down onto the hotplate (which has to be a fair bit hotter than the boiling liquid) and catches fire.
I know, I've done it.
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