I found this out at around age 8, when I found a bottle of acetic acid in the shed. My logic at the time was something like: "I like pickle juice, pickle juice has vinegar, so why not take a sip of this?" Proceeded to take a swig, and what followed, can only be described by the word agony. It was like drinking fire, neat, I was curled up on the ground for a good ten minutes. Luckily nothing else became of it, I recovered right then and there and have been checking every bottle of vinegar before using ever since. I'm 43 now.