You know those mugs people buy from tourist locations with etched scenes of the St. Louis arch, or the Statue of Liberty? Those are etched with hydrofluoric acid, which is my new favorite type of burn. It's perfect for an ER doc--bad and treatable, so it combines toxicology with trauma.
The below is a picture of an HFA burn, which doesn't present as pictured initially. Just like pain out of proportion with exam is a marker for mesenteric ischemia, pain out of proportion with burn is a marker for HFA burns. Why? The fluoride ions diffuse through the skin easily and proceed to precipitate out with calcium and magnesium ions, destroying deep tissue; the consumption is so marked that patients can present with hypocalcemia and hypomagnesemia.
Treatment is to give the acid what it wants; calcium gluconate to the skin, which attracts the fluoride ions and causes a precipitate. That's the white crust seen above--vigorous application of calcium gluconate jelly every hour created a calcium salt on the skin. It also was replaced intravenously and intraarterially in the above case.
Medicine is 'fun' (since I can't use fun without quotes when talking about someone getting their hand burned off) when you have recognizable symptom complex with a clear antidote.
Of course, I haven't actually seen such a patient. My only hope is to file the knowledge away and hope it is still recall-able when I do see it.