Antoine Lavoisier

The life of the French scientist, including how he discovered Oxygen.

Antoine was born Antoine-Laurent Lavoisier on the 26th of August 1743 to a wealthy upper-class French family. Antoine gained a degree in law from the Collège Mazarin, but his true interests were in Science and Mathematics. He began to pursue these interests from the age of 21, by studying geology, astronomy and botany. In 1786 he was accepted into the Academy of Sciences after a winning essay on the best means of lighting a large city at night.

He was married in 1771, to Marie-Anne Pierette Paulze (who was 13 years old at the time). Far from holding back Antoine’s career, Paulze learned English so that she could translate the works of earlier scientists. She also drew many of the sketches of Antoine’s lab and equipment, as well as those which were featured in his book, Traité Élémentaire de Chimie (Elementary Treatise of Chemistry).

Up until Lavoisier’s work, many scientists still believed in an invisible substance called Phlogiston. The theory behind phlogiston was that in all combustion of materials, phlogiston was released. All flammable substances were said to contain phlogiston. Scientists of the ancient world developed this theory when they realized that wood ash and iron rust (both known as “calx”) were lighter than the original substances. At the time people believed that materials were composed of both calx and phlogiston, and that weight was reduced when phlogiston was released during combustion. It was also theorized that when a material in an air-tight container stopped burning, it was because the air around it had become saturated with phlogiston (this was called “phlogisticated air”) and could no longer support combustion.

Lavoisier came up with a different theory; he said that the mass of a mixture remained the same throughout chemical reactions. He also believed that, during combustion, materials did not release phlogiston, but took in another gas. In effect, Antoine’s gas was the polar opposite of phlogiston. Antoine called his new gas “oxygen”. He attempted to prove his ideas in 1777, by heating a bell-jar of air and mercury for 288 hours. After the mercury “calx” had formed, Lavoisier measured the volume of air inside the jar and found that it had decreased by 16%, and that all of the remaining gas was what we now call Nitrogen. This proved that oxygen had been used up in forming the calx and that no phlogiston had been released. Four years later, Lavoisier further proved his theories by splitting water into oxygen and hydrogen, then recombining them to form the same volume of water. When he published Traité Élémentaire de Chimie, Antoine named thirty-three different chemical elements as well as explaining his oxygen theory.

Eventually, people accepted Lavoisier’s ideas and phlogistonists gave up their arguments.

Although Antoine Lavoisier became a success, he was eventually consigned to a cruel death: earlier in his life, he had invested in the Ferme Générale, a company which collected tax on imported goods. Lavoisier did not abuse his power, but many others did, and during the French Revolution, all members of the Ferme Générale were imprisoned. On the 8th of May 1794, fifty-one year-old Antoine-Laurent Lavoisier was placed on a guillotine and decapitated.

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