Subject: Re: liquid nitrogen
From: glhurst@onr.com (Gerald L. Hurst)
Date: Mar 18 1997
Newsgroups: rec.pyrotechnics

In article <5gkmni$lus@camel1.mindspring.com>,
jakemont@mont.mindspring.com (Jake Stewart) says:

>where could I get liquid nitrogen for making a potatoe gun?

Another vice presidential hopeful, eh?  Potato(e) gunnes are
made from PVC, not liquid nitrogene.  If you insist, you can buy
all manner of liquid aire and its components from Air Products.

Working with high pressure gases can be just as dangerous as working 
with explosives.  The mere fact that you are looking to do what
you want to do the hard way means you should wait until you know
more about how these things work.

Using liquid nitrogen as a pressurizing agent is a job for a chemical
engineer not a novice.  You'd be surprised how quickly that little
pressure gauge can move from not much to thousands of PSI and climbing.
BOOM.

I knew an engineer who learned about cryogenic gases the hard way.  He 
was supervising one of the shifts at a pilot plant I had designed at 
Aerojet.  The process had a step in which liquid fluorine was vaporized 
to a certain volume at a pressure of a couple of thousand PSI.  The man 
got in a hurry and neglected to allow for a plug of some frozen impurity 
in a transfer line.  As he left the plant head first, he noted the 
pressure gauge passing 4,000 PSI at a frightening rate.

I had to rebuild my new pilot plant.  It wasn't the reactivity of the
fluorine that did us in -- it was simply the pressure generated as
the cryogenic liquid became not so cryogenic.  It's a good thing we 
had sand-bagged the facility.  I'll bet you're neither as experienced 
nor as lucky as the guy that made the mistake.


Jerry (Ico)