Jean-Baptiste van Helmont

Educated at Leuven, Van Helmont practiced medicine during the plague in Antwerp before settling at his estate in Vilvoorde. Refusing to accept the ancient Aristotelian four elements, he conducted meticulous quantitative laboratory experiments with balances.

He showed that burning charcoal produced a distinct substance different from atmospheric air, which he named 'gas sylvestre' (carbon dioxide), deriving the word 'gas' from the Greek 'chaos'. In his renowned willow tree experiment, he demonstrated that the tree's 164-pound gain in mass came from water rather than soil.