Tom James  of the Southampton University Chemistry 
Dept writes: 
     
 Liquid nitrogen, then. Pretty boring stuff, you might think... but
you'd be wrong. When you're stuck in a laboratory on a Friday afternoon it 
can be an endless source of amusement. Many times have I innocently looked 
on as a colleague has picked up a lab report from a lab bench only to see 
it crumble into a myriad of icy shards. "Er... sorry! I must have spilt 
some N2. Erm... I've got some sticky tape here..."
 But that was in my wild and rebellious youth.  Something happened
a while back which made me mend my ways. I've never told anyone about it 
before, but I may as well come clean now. Here goes...
     
 Liquid nitrogen is cold. Very cold. Extremely cold, in fact. 
 Think about a bad day on the South Pole (minus 80 degrees), then
multiply that by two. Liquid nitrogen is colder than that.
 Minus 196 degrees centigrade. Dip something in it and expect to
see something else emerge. Something that shatters in the twinkling of an 
eye. Like a lab report, for instance.
 So there I was, on a hot June day, stuck in a laboratory, gazing
out of a window, dreaming.
 "Excuse me."
 "Mmmm..." 
 "We've run out of N2... er..."
 I turned around. It was a first-year. Strangely enough. "Yes?" 
 "Well... er... there's none left."
 "OK, OK. Don't panic. I'll get some." I wandered absentmindedly
out of the lab and down towards the store room. When I arrived, however, 
I realised that I'd forgotten to bring a vacuum flask with me.  Such 
flasks are essential in the transport of this stuff in order to avoid 
severe frostbite.
 Great. I looked around the store room. No vacuum flasks in
evidence... but wait a minute, what's that in the corner? I walked over 
and picked it up. It was an old and dusty vacuum canister, used (but not 
recently) for carrying liquid nitrogen over long distances. It had its 
own lid with a cute little safety valve on top. Thank God for that, I 
thought as I poured out some N2 into it. I won't have to walk all the way 
back for a flask. I finished pouring it out, put on the lid, sealed the 
lid catch (which was a bit stiff) and began to walk back.
 I stopped suddenly.
 What the hell was I doing? I'd just put some liquid gas into a
sealed canister which was probably about twenty years old, and I hadn't 
even checked the safety valve. I gave the canister a shake and put my ear 
against the valve.
 I should have heard it hissing slightly. 
 Nothing.
 I should have felt a breath of cold air against my ear. 
 Nothing.
 Well, so the safety valve doesn't work. No problem. I'll just take
the lid off. I tried to release the lid catch, but strangely enough it 
refused to budge.
 Now, I like to think that on the whole I'm a calm and unflappable
individual not usually given to attacks of panic in dire situations. But 
I can tell you, noshing friends, that at this moment a few beads of sweat 
were beginning to appear on my forehead.
 Deep breath. Don't panic. Don't do anything rash.
 I put the canister on the floor, placed my foot on it and with
all my strength rashly pulled back on lid catch, which promptly snapped 
off leaving the lid sealed in place.
 This was bad. In fact, this was extraordinarily bad. 
 I stared at the container in disbelief. Why me? Why was this
happening to me? This was supposed to be CH213 Kinetics and Quantum 
Chemistry not BM101 Elementary Bomb-Making. With the safety valve u/s and 
the lid sealed on this thing was going to explode. And it was going to 
explode in about an hour or about a minute, depending whether or not Pluto 
was in my third house with Saturn rising. Pot luck, in other words.
 Right. There's a time for cool-headed action and there's a time
for blind and total panic. This was a time for blind and total panic. I 
grabbed the canister, sprinted down the corridor and began to leap down 
the stairs to the basement.
 Once there, I ran down the basement corridor, reached the door of
what I thought was the hazardous waste room, pulled it open, threw in the 
bomb, slammed the door, and collapsed against the wall of the corridor.
 A few seconds later the door opened. I looked up to see a man in
a white coat emerge from the room carrying the canister. He looked down 
at me in consternation.
 "Excuse me," he said, offering me the aforementioned object. "Is
this yours?"
 "Er... yes." It was one of those surreal moments that only happen
in real life. I took it from him. "Thanks."
 He went back inside and as he closed the door behind him I saw
the sign on it.  `Synchotron Photo-electron Spectroscopy'.
 Wrong room. 
 So much for blind and total panic.  
 I ran the rest of the way down the corridor, reached the real
hazardous waste room (I checked the sign this time) and pulled on the 
door.
 Locked.
 I legged it back towards the stairs, leapt up them three at a
time, and fell gasping into the ground floor lobby, still clutching the 
nitrogen canister.
 "Ahh... erm... I'm sure this gentleman will be pleased to show
you around the building, won't you... erm..."
 I wiped the sweat out of my eyes and looked around the lobby. I
was surrounded by a crowd of grinning schoolchildren.
 "Er... won't you... erm..." said the teacher in attendance.
 Well, if this wasn't a total bloody nightmare before it certainly
was now.  I could almost see the headlines already. Mad Suicide Bomber 
Kills Party Of Schoolkids.
 I mumbled an excuse, blundered my way through the bemused throng,
and stumbled out of the building. I looked at the canister in my hand. 
Was I destined to carry this thing around with me for ever? Was this my 
`albatross'?
 I looked at it more closely. It was beginning to bulge.
 That was enough to give me a second wind. In fact, I don't think
Linford Christie could have made it across the campus faster than I did 
that day.  I reached the little spread of greenery on the other side of 
the university, and to the amusement of several onlookers, threw the 
container into the duck pond and hit the deck.
 I think I must have lain there for several minutes. I can't really
remember.  There certainly wasn't an explosion, because I do remember 
sitting by the pond for the rest of the day waiting for it to go off. 
Perhaps it had a slow leak.
 To this day though I always give that pond a wide berth.  Just

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