Antoine Lavoisier

Antoine Lavoisier established modern chemistry by insisting on the balance, and was guillotined during the Terror. Born in Paris in 1743 to a wealthy lawyer, he inherited a fortune, trained in law to please his father, and studied chemistry, botany, geology and astronomy alongside it. At twenty-six he bought a share in the Ferme générale, the private consortium that collected taxes for the crown, which funded the finest laboratory in Europe and eventually killed him. He married Marie-Anne Paulze, thirteen at the marriage, who learned English and Latin to translate for him, took drawing lessons from Jacques-Louis David to illustrate his work, and kept his laboratory notebooks — a genuine collaborator. His method was quantitative. He weighed everything, including the gases, in sealed vessels, and from that established the conservation of mass: matter is neither created nor destroyed in a reaction, only rearranged. He demolished the phlogiston theory, which held that burning released a substance. Lavoisier showed that combustion and rusting are combinations with a component of air, which he named oxygen, and that metals gain weight when they burn because they absorb it. He demonstrated that water is a compound of hydrogen and oxygen, not an element, and that respiration is a slow combustion. His Traité élémentaire de chimie of 1789 provided a systematic naming scheme and a list of elements, and is the first modern chemistry textbook. He was a reformer who worked on gunpowder, agriculture, hospitals and the metric system. The Revolution nonetheless condemned the tax farmers, and he was executed on 8 May 1794. Lagrange said it took a moment to cut off that head, and a hundred years might not produce another like it.

• Lived: 1743 CE – 1794 CE
• Nationality: French
• Roles: chemist, scientist