Antoine Lavoisier

Antoine Lavoisier showed through precisely weighed, sealed vessel experiments that combustion and respiration both consume a component of air he named oxygen in 1778, and that water is a compound of oxygen and hydrogen rather than an element. His 1783 paper Reflections on Phlogiston dismantled the century old phlogiston theory of combustion, and his careful accounting of mass before and after chemical reactions established the law of conservation of mass. He was guillotined in 1794 during the French Revolution, convicted along with other tax farmers of the Ferme Generale. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/