Alchemy's sulfur, salt, and mercury - do they make sense on any level?

no, i'm not suggesting reality works in the way described by alchemists, but looking at things like the four elements as symbols or figurative traits, it makes a sort of sense, and i'd like to use this triad idea in fantasy fiction. can anyone explain sulfur, salt, etc. in any way, from pre-modern science theories of matter to spiritual archetypes, w/e?