Antoine Lavoisier described to the French Royal Academy of Sciences in 1783 experiments that show water to be a compound, not an element.
Characteristic of Lavoisier’s chemistry was his systematic determination of the weights of reagents and products involved in chemical reactions, including the gaseous components, and his underlying belief that matter—identified by weight—would be conserved through any reaction (the law of conservation of mass). Among his contributions to chemistry associated with this method were the understanding of combustion and respiration as caused by chemical reactions with the part of the air (as discovered by Priestley) that he named “oxygen,” and his definitive proof by composition and decomposition that water is made up of oxygen and hydrogen. His giving new names to substances—most of which are still used today—was an important means of forwarding the Chemical Revolution, because these terms expressed the theory behind them. In the case of oxygen, from the Greek meaning “acid-former,” Lavoisier expressed his theory that oxygen was the acidifying principle. He considered 33 substances as elements—by his definition, substances that chemical analyses had failed to break down into simpler entities.
Visit Chemistry in History to learn more about Antoine-Laurent Lavoisier.
Excerpted with permission, Chemical Heritage Foundation