|"PET-MIPS-anim" by Jens Maus (http://jens-maus.de/) - Licensed under Public Domain via Wikimedia Commons|
For you writers, here are some interesting twists. Symptoms of exposure to hydrofluoric acid may not be immediately evident; the delay can take anywhere from 8 to 24 hours, and the burns may not be painful since the acid damages nerves.
Plenty of time for a villain to make a getaway.
Like some other poisons, fluorine has a life-saving use in the medical field. Fluorine-18, an isotope of fluorine, is often found in radioactive tracers for Positron Emission Tomography (PET scan). The most common tracer is fluorodeoxyglucose which, after IV injection, is absorbed by glucose-loving tissues such as the brain and most malignant tumors. (See very cool PET scan image above.)
It has a half-life of about 109.771 (which is about 20 minutes). So after your scan you won't stay radioactive forever. Or am I the only one who worries about these things?