I look at it from a different angle...
Why was it abandoned?
- He was doing things forbidden by The Alchemists Guild (Give the guild a cool name) - which then makes you consider "what would be forbidden?" which is a sub-string of potential adventure ideas.
- He discovered some Alchemical secret the forced him to go in search for more clues. For this to work, you have to have an idea of some element you want to add to your game, or be a MacGuffin to lead your PC's along to further adventures on the trail of whatever the Alchemist discovered; maybe they left to find some part of the puzzle to their discovery? Some rare ingredient they were missing?
- The alchemist was assassinated/abducted, but before he died he left a clue about his work and the potential people that removed him. This could be a Breaking Bad scenario where he was in the employ of nefarious individuals that you can set up in your game later for something bigger. So was he cooking drugs? Poison? Kingdom-endangering Zombie virus?
- It's abandoned because He Done Fucked Up*. He created something that removed him from the premises. Perhaps it changed him in some innocuous way - Made him Ethereal? Shrunk him (and maybe some of that formula is laying around - you can have an entire adventure where the party is shrunk down and has to adventure WITHIN the abandoned building - you could fill it with all kinds of new biomes and maybe even find the Alchemist himself who has been working in tiny-mode for years to craft an antidote. But because of his size he's limited, and the Ants. And the T-Rex sized spiders of the Cobweb Forest! And the RATS! The Roaches. Traversing the Dirty Floor of Desolation is rough work! It turned him into a local monster that plagues the region... like his master before him. It gave him some kind of allergy to sunlight... and forced him to live underground... and deep in the cellar the PC's find a secret door that goes down... down... down. Did he dig too deep?
Or you know... you can just scatter a bunch of stuff around - vials, beakers, pots and pans... boring obvious stuff