Reminds me of the time I was working on a remote repeater site and called down to the landowner to bring me some water for the batteries. His father brought up a couple gallon jugs of what was supposed to be filtered water. I started pouring the liquid from them into the batteries and had an eruption shortly thereafter. Apparently the old man had mistakenly brought me up a couple of jugs of 10 molar muriatic acid. The problem was, these were in the sort of 1 gallon plastic jugs typically used for water or milk, with no labeling on them at all.

The scary part; it was in the 90s that day, and I was contemplating taking a big swig before putting any in the batteries. That one had me contemplating life for a bit.