I've recently began full development of a character with a solid background in Alchemy using the GURPS. While I could have a character that is mainly an alchemist, the system itself doesn't provide much leeway into creating a PC as a viable alchemist - especially when it comes to an adventuring/travelling campaign, so it's left more to NPCs with ridiculous levels in the skill so PCs have something to buy alchemically.

So, I've given the character a basic travellers alchemy kit, which would allow for her to create some elixirs and potions she knows/has a recipe for that aren't too complex and don't have a lot of time needed to invest. But the GURPS rules on alchemy also state that the specialisation goes beyond just potions and elixirs that are defined in various supplements and delves into basic chemistry as well.

Now, I don't have a very solid background in chemistry, nor a history of it back in the renaissance (which is around the time the campaign is set in a fictional world). So what basic general chemistry would an alchemist have the knowledge to pull off back in those times that would be of use while adventuring, or even at all?

Also, alchemy general. (pic semi related as Doom is an alchemist as well)