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Ammonium nitrate + mortar/pestle = death?? Answered

How risky would it be to crush crystalised ammonium nitrate (like in instant cold packs) in a ceramic mortar and pestle?

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Kiteman (author)2008-02-10

Absolutely no hazard whatsoever.

Ammonium nitrate is an oxidiser - it doesn't burn or explode, it helps other stuff burn and explode. Mix it with a fuel (charcoal, sugar etc) and grind it vigorously and then you're in trouble.

Bit of advise - ammonium nitrate is hygroscopic - it absorbs water easily from the air around it - so keep it stored in an air-tight container.

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Austringer (author)Kiteman2008-02-10

Chemical energy comes from chemical bonds. You can figure out how much energy in a gallon of gas by adding up the energy of all the bonds in gasoline and subtracting all the energy in the carbon dioxide and water vapor it will produce. Stressed bonds hold more energy the unstressed bonds. Acetylene has scads more energy than ethane. Things that are shock sensitive usually derive their energy from highly stressed bonds. They want to, in a thermodynamic sense, fall down and once one goes, it's more than enough to set it's neighbors off. Things that require oxidizers (like gun powder) generally need more of a push to get the ball rolling (in that same thermodynamic sense). This is why your car uses spark plugs and why bullets have primers. The Wikipedia article on primary and secondary explosives covers this nicely. NOTE: sometimes things can react with an oxidizer to form something that is very shock sensitive. "Peroxides kill chemists" or so the saying used to go. A little knowledge can be a dangerous thing is still in vogue. Just saying.

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Kiteman (author)Austringer2008-02-10

Things that require oxidizers (like gun powder) generally need more of a push to get the ball rolling (in that same thermodynamic sense).

Normally true, but grinding by hand can generate quite a bit of heat. A couple of years ago (maybe 3 or 4 now), a UK science teacher lost his job after a practical lesson on how to make gunpowder by historical methods (i.e. grinding by hand) cost a pupil four of his fingers.

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Austringer (author)Kiteman2008-02-10

Yeah, I should have been more explicit there. Also, of course, if there is any chance of a spark, like if you're using steel tools, you're asking for trouble.

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Big Bwana (author)Austringer2008-06-25

And some plastic tools which can develop a static charge when used....

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killerjackalope (author)Kiteman2008-02-10

or use a magnesium mortar and pestle, that would be funny, or aluminium, or potassium, this is something I'll end up making...

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Dirtbiker460 (author)2008-02-10

Thanks guys for your replies. After more research, turns out I have no use grinding up AN anyways...

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VIRON (author)2008-02-10

Crushing toy-gun-caps is probably more scarey. I don't think anyone ever died from crushing a cold pack.

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astrozombies138 (author)2008-02-04

WTF ARE YOU THINKING!?!? ARE YOU TRYING TO BLOW THE ENTIRE WORLD UP YOU CRAZY CHEMIST!!!!?!?!! (really I have no clue the kid in the video did it just fine i guess)

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