[Hrothgar]

In a cinematic campaign, a villain with chemistry and Gadgeteer could be fun. You could get around actual chemical knowledge my labeling concoctions as "Compound X" or "Homebrew Acid".

A character that realistic campaign, with detailed knowledge of chemistry IRL, and a character with a high chemistry skill... Probably doesn't need to roleplay this in a game and should be a real chemist, lol.

In all seriousness though, most complicated skills that the average joe doesn't know the detailed workings of can cause problems if someone wants to pick at the way it works in game.