Tons of stuff.

And I've answered this exact question many times:

https://www.reddit.com/r/AskHistorians/wiki/profiles/bemonk

But it's one of my favorites and one of the reasons I do the History of Alchemy Podcast.

Alchemists, on their search to creating the philosopher's stone discovered many compounds and synthesized many materials.

They discovered:

• Elements like phosphorous and described oxygen
• That medicine is a thing, and not just the 4 humors
• Porcelain in Europe
• Tanning
• Many dyes like Prussian Blue and reds

And then they also classified minerals (and everything, really) and invented the basic tools for chemistry. Not just the glass vessels, but advanced furnaces with control systems. They ran experiments that were reproducible and to test hypothesis. It definitely wasn't a straight line from alchemy to chemistry... in fact I spend dozens of hours talking about the journey on my podcast. See my other answers in the first link for a more detailed list and more detailed examples.