There is this one awesome example of it, being used to dissolve physcicist's gold nobel prizes, sparing it from a nazi raid during the war, the gold was precipitated out later and recast and presented to the physicists again.
As others have pointed out, the basic chemistry for B&W is pretty safe when common sense is used. But some photographers eventually begin to delve into the "dark arts" of mixing their own chemistry which involves working with raw compounds that can cause problems if not treated with respect. if one reads the MSDS for catechol (http://fscimage.fishersci.com/msds/04360.htm) you might just run, not walk away even though it is a compound in one of the best film developers you can make from scratch or from a kit.
As you move into the various realms of alternative processes, you begin to work with various carcinogenic compounds and heavy metals. Wet plate collodion uses a bunch of potentially harmful chemicals from cadmium, to silver nitrate to KCN yet it is one of the most rewarding of all photographic processes. The key is to treat all chemistry with respect and research any new process thoroughly with regards to the handling of chemicals.
PE: HF is kept in an HDPE bottle. Sorry to hear about your she-friend's itch:)
lol, I mix developers together all the time. OSHA would love meeeee.
Nitric + hydrofluoric doens't make aqua regia as pointed out above.
But when I worked in an analytical testing lab I once recieved a bottle of nitric and hydrofluoric for testing from a chrome plating shop - it was a pickling bath solution. The liquid in the bottle was dark green and weighted much more than the same amount of water (or those two acids) whould have from all the dissolved metals in it.
The outside of the bottle was labelled "MF Acid". I showed it around to some of the old timeres there and asked if MF acid was some sort of special industry name they had heard about before - none of them had. But every one of them suggested that is stood for "motherf***en" acid.
I tested it and it was 35% Nitric, and 10% HF. I think I'd call it MF acid as well if I worked with that on a routine basis...