Stahl, Georg Ernst (1660-1734)

German chemist who developed the theory that objects burn because they contain a combustible substance, phlogiston. Substances rich in phlogiston, such as wood, burn almost completely away. Metals, which are low in phlogiston, burn less well. Chemists spent much of the 18th century evaluating Stahl's theories before these were finally proved false by Antoine Lavoisier.

Stahl was born in the principality of Ansbach and studied medicine at Jena. He became a physician to the duke of Saxe-Weimar in 1687. As professor of medicine at Halle 1694-1716, he also lectured in chemistry. From 1716 he was physician to King Frederick I of Prussia.

The phlogiston theory was the first attempt at a rational explanation for combustion and what we would term oxidation. Doubt crept in only when chemists began weighing the products of such reactions, which should always have been lighter, having lost phlogiston. Stahl accounted for observations to the contrary by suggesting that phlogiston was weightless or could even have negative weight.