Oddbean new post about | logout
 Oops. I read Fluoride 😆  
 Hydrofluoric acid is fluoride but PFAs are where you take hydrocarbons and reduce the hydrogens off and substitute with fluorine. So technically PFAs contain fluorine. But fluorine is aggressive stuff and will eat almost everything, it has the highest pka and can drive even sulfur off stuff, which is otherwise the most resistant acid ion in salts... IE, if you get HF and put it on gypsum it forms calcium fluoride and sulfuric acid.