Yes, but not loudly, waving it around, while I am explaining the safety protocols for laboratory use of silver nitrate in chemistry class.

It’s dangerous stuff, as you can see here:  http://www.sciencelab.com/msds.php?msdsId=9927411.

Did this actually happen? Of course — I don’t think I could make up a story like that. It happened in a different class than the one I am teaching this year, though. The student’s name is being withheld, to protect his identity (and my job).