Jābir ibn Hayyān

Laid down the experimental method in writing 800 years before Bacon — and a sulfur-mercury theory of metals that was wrong but productive for a millennium.

The Jabirian corpus (likely a school under one name) refined distillation, crystallization, sublimation, and calcination into reproducible lab procedures, and isolated or characterized citric, acetic, and tartaric acids along the way. The corpus also proposed that all metals were composed of sulfur (combustibility) and mercury (metallic-ness) in different proportions — which is wrong as physics but turned out to be a usable working model that organized centuries of European experimentation. The procedural rigor is the lasting gift; the metaphysics was scaffolding.