Per Uncle Monster:
Mercaptan is a great prank substance for chemistry students to play with even more powerful a
terrorist weapon than hydrogen sulfide. My oldest brother and his pals went into the chemistry
lab at school, dissolved hydrogen sulfide gas into a jar of cold water, took the jar to the cafeteria,
placed the open jar on a radiator then slunk away. It was like the Jolly Green Giant farted in there
and it cleared the room. The monks had their suspicions but couldn't prove which miscreant did the deed.

Maybe that's the stuff your chemistry teacher used to keep us under
control. The threat was that if we didn't behave, he would un-cork a
bottle of the stuff in our classroom. He did do it once... and that
was plenty for us...
--
Pete Cresswell