From sci.chem Wed Dec 11 09:13:55 1996
From: "Keith D. Wilkins" <wilkinkd@a1.spoc2.umc.dupont.com>
Subject: Re: Lab Accidents.......

I was participating in a Chemistry demo about ten years ago when the value
of trying a new variation of an experiment in the lab before you do it in
public was reinforced.  The demo was the old Ira Remsin experiment.  We
used a round bottom flask with about 50ml of nitric acid and then dropped
in a couple pennies.  The flask was then capped with a rubber stopper with
hole and some tubing that went to a 1.5 gallon goldfish bowl filled with
water.  We had done this particular demo 10-15 time before.  One problem
that always occurred was that a little bit of the NOx gas evolving and
bubbling through the water would escape.  We would cover the water bowl
with some Saranwrap and a rubberband but a little of the brown gas would
still leak out where the tubing entered.  For this particular show one of
the guys had the bright idea of sticking a plastic disposable pipette tip
into the end of the tubing under water on the theory that the bubbles would
be smaller and more effectively scrubbed.  We would usually do these shows
with about 4 people to keep things moving along and I am still glad that my
friend Tim had the honor of doing this experiment while it was videotape as
an example for other groups wishing to set up these types of chem demos. 
What happened is that the pipette tip created too much back pressure and as
Tim is standing there in front of the fascinated 7-8 year olds the cork
blew and a big cloud of NOx blows up in front of him.  He quickly reacted
and grabbed the cork and replaced it but it blew again about 10 seconds
later with similar effects.  He covered the top of the flask with his hand
and the guy who had installed the pippette tip ripped open the top of the
water bowl and cut the tubing with a knife.  The cork was then replaced and
the rest of the experiment went relatively normally.  Back at the lab we
watch the video many times to enjoy Tim's performance.  After that however
I designed a scrubber system using three bubbler tubes that effectively
removed the NOx without generating too much back pressure.  We did test it
before we used it in a show.

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