On Sun, 12 Jan 2003 18:14:00 EST, [EMAIL PROTECTED] wrote:
>Take
>some advice from someone who knows all the issues involved
Take some different advice from someone else who knows all the issues
involved, and a few other issues as well: don't be put off because
some "expert" tells you peroxide is too dangerous for mere mortals to
work with. That expert was a mere mortal once himself, though he may
have forgotten that humble epoch. He didn't get to be an expert by
being cowed by pronunciations of doom from on high, nor should you.
I'm not saying ignore the experts. We've been there and done that and
lived to tell the tale. I'm saying ignore the experts who
condescendingly clamor about how dangerous it is without explaining
why it's dangerous, and attend those who tell you what the dangers
are, and what you'll have to do to do the work safely. Even if they
won't, for liability reasons, tell you _how_ to do the work safely.
:-)
As I've said before, vapor distillation is the obvious method of
refining a liquid, but it is the most dangerous method of refining
peroxide. Peroxide vapor pressure is pretty low, and a still has to
work at high temperature to produce a useful amount of peroxide vapor.
The problem is twofold: one, peroxide decomposition is exothermic
(2H2O2 -> 2H2O + O2 + heat), heat accelerates peroxide decomposition,
accelerated decomposition in a still raises the pressure, pressure
also accelerates peroxide decomposition, and now you have all the
ingredients for a double positive feedback loop, which very rapidly -
as Ian says, it can happen in less then a second - leads to a runaway
reaction ending in a BLEVE. A BLEVE is a boiling liquid expanding
vapor explosion, and it's nasty: as the vapor overpressure falls off
after the initial spike, the boiling liquid continues to produce more
vapor. So the explosion continues even after the pressure vessel
ruptures. That will spray the surroundings with boiling peroxide, a
nice bonus after they've been sprayed with shrapnel from the exploding
pressure vessel.
But it gets better. A BLEVE is mild compared to what _can_ happen to
a peroxide still. The second part of the problem is that peroxide
vapor is a high explosive, just like TNT and C-4. If you get peroxide
vapor hot enough, and keep it hot long enough, it can and will
detonate. While a BLEVE will wreck the pressure vessel containing the
boiling liquid, a detonation will destroy everything near it. What
isn't vaporized will be pulverized. No sewing back on of fingers,
because they're in many pieces scattered over several acres.
And *that* is why you don't want to use vapor distillation. You can
avoid both BLEVEs and vapor detonations by keeping the still merely
warm, not hot - but then it won't work.
Use sparging and/or fractional freezing. Have lots of water on hand,
read the MSDS, don't spill it on wood, all the usual superoxidizer
cautions. At least it isn't cryogenic. :-)
This, BTW, is why I said your project will be expensive: you can't do
just one thing. There are cheap ways to do peroxide rocketry, and
safe ways to do peroxide rocketry, but there are no cheap safe ways to
do peroxide rocketry.
And still I don't advise you not to try it. I advise you to know the
costs and the risks, proceed with safety, and scale the project to
what you can afford.
-R
--
"You haven't been lost until you've been lost at Mach 3."
-- Paul Crickmore
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