Totally irrelevant, but it reminded me of this one:

Little Johnny was a chemist,
but Johnny is no more,
for what he thought was h20
was h2s04

Thom Fitzpatrick
thom@calweb.com - http://www.calweb.com/~thom
Keeper of the Barndoor Bus Web Page: http://www.calweb.com/~thom/barndoor.html