We all have experiences with chemicals that stick in our memory. Experiences where we have witnessed just what chemical potential really means.  Proton or electron transfer can be downright frightening sometimes. Rude and abrupt phase changes or angry exotherms. Sometimes nature rages back at our feeble attempts to take the dragon out for a walk on a short leash.

I can name many exciting materials, but I think that chlorosulfonic acid is one of the more exciting and obnoxious substances that isn’t explosive or neurotoxic.  What are your favorites?