Poison

[WallShadow]

This bit of trivia popped back up from high school chemistry while I was contemplating alternative methods of refrigeration. Old (very old) models of refrigerators used sulfur dioxide as a refrigerant. Which is all well and good as long as it stays in its sealed loop and, like Gremlins, _never_ comes in contact with water.
Otherwise--instant sulfuric acid. Not pleasant against the skin, and even less pleasant to breathe when aerosolized.