From sci.chem Mon Dec  9 16:49:32 1996
From: wpenrose@interaccess.com (William R. Penrose)
Subject: Re: Lab Accidents

pclarke@waite.adelaide.edu.au (Philip Clarke) writes:
> so I have a few litres of liquid nitrogen left over.

Reminds me of yet another story (not a real accident, but nearly....):

IN grad school, I was doing the familiar trick of freezing some rubber tubing 
in LN2 and smashing it with a hammer, but instead of an open dewar, I was 
using the main 5 gallon LN2 tank, which had a spout about 1 cm in diameter.  
So I pushed the tubing in, it froze, and then stuck.  Since I couldn't pull it 
out, I just left it.  But somebody  noticed that the familiar little puff of 
frost was no longer showing above the dewar spout.  The frozen tubing had 
plugged with frost.  We realized that there would be a lot of pressure 
building up inside, so we set about trying to get the tubing out.

It just got more frozen and more stuck each time we tried, so finally I got a 
screwdriver and hammer and risked breaking the inner glass wall, and just 
drove the rubber into the flask with one hard blow.  A foam of LN2 shot out of 
the dewar for (it seemed) several minutes until the pressure was relieved.

I've sometimes wondered just how bad it would have been if my buddy hadn't 
noticed that the gas wasn't escaping.

Bill



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