How did Antoine Lavoisier explain combustion?

Antoine Lavoisier replaced the prevailing phlogiston theory—which incorrectly posited that a "fiery substance" escaped during burning—with his own oxygen theory of combustion.12

Lavoisier’s breakthrough was rooted in the law of the conservation of matter, which states that the total amount of matter remains constant. Through precise laboratory measurements, he observed that when substances like sulfur or phosphorus burned, the resulting products weighed more than the original materials. He concluded that this weight gain occurred because the burning substance combined with a specific component of the air.32

After learning of Joseph Priestley’s discovery of a new type of air, Lavoisier identified this gas as oxygen, the "generator of acids". He demonstrated that combustion is not the release of phlogiston, but rather a chemical reaction between a combustible substance and oxygen. This discovery was a foundational moment in modern chemistry, shifting the field toward a system based on accurate measurement and the identification of elements.23