Birdduke said something about them having access to sulfur I think? This came up in the last chemistry conversation that I don't remember super clearly. They may have access to potassium nitrate, which we historically had by the first century in China. With sake, they have access to at least simple distillation, and given that it doesn't seem to just be Jashin-damned firewater that blinds people every so often they almost certainly have fractional distillation. They can forge and work steel, which implies things not just about their mining and metallurgy advances, but also that they have access to high energy fuels such as coke. If we've ever seen etched glass, that almost certainly implies the presence of strong mineral acids. They have soap, so they have lye. I'm not sure if they understand the distinction and relationship between bases and acids yet though.
All in all, a good place for us to estimate around is probably somewhere around where the Islamic alchemists were in their golden age.
