So, aqua regia is a somewhat safe material for a living being to work with, but the problem is that it isn't metal enough.
Somebody suggested in an answer to another question, that dragons would fare better if their breath weapon was sulfuric acid, as it'd start acting immediately and cause nasty 3rd degree burns.
I was like "Then why not go piranha solution?", but before that, I wanted to get something out of the way. Aqua regia, more precisely, its two components are safe to handle, but sulfuric acid is rather dangerous.
Would it even be possible for a dragon to safely use sulfuric acid as their breath weapon? If yes, how can they keep it from damaging them while inside their body?
Update: Look at this article, that I just found: https://www.sciworthy.com/mining-with-acid-generating-bacteria/
I'm not sure if a dragon could make use of it, though. There are some bacteria that survive in highly acidic environments, and produce sulfuric acid as a byproduct, but I don't know if they can deal with 0.1 pH.