Antoine Lavoisier

In the 18th century the discoveries of the French scientist Antoine Lavoisier were so important that today he is thought of as being the founder of modern chemistry. He was one of the greatest scientists in history.

ANTOINE’S EARLY LIFE

Antoine was born on August 26, 1743, in Paris. His father was a prosperous lawyer, but when Antoine was five his mother died and he was looked after by an unmarried aunt. Although interested in science as a child, while at school he mainly studied Ancient Greece and Rome, as well as literature. There were few jobs in science, and so when Antoine left school he became a lawyer, qualifying in 1764. He also worked for the French government, helping to make improvements in both farming and taxation. This changed in May 1768 when Antoine won a prize for an essay on street lighting in Paris. He was also elected as a junior member of the Academy of Sciences, the most important scientific institution in France.

SCIENCE IN THE 18TH CENTURY

This period in history was known as the Age of Enlightenment. There was a growing interest in science, but little had been discovered. Before this time, many people had attempted to discover more about chemical compounds and reactions, but they were hardly scientists or chemists as we now think of them. They were known as “alchemists”. Alchemy was a combination of science, art and magic, and had been practised for hundreds of years. Alchemists and many others agreed with the work of the Ancient Greek philosopher Aristotle that the world was made up of four “elements” known as earth, air, fire and water. Many believed that these four “elements” contained something called phlogiston, a substance released during a process known as combustion (burning).

WHAT DID LAVOISIER DISCOVER?

Lavoisier built on the work already done in the 1770s by the English scientists Henry Cavendish and Joseph Priestley. He became the first person to isolate and name the element oxygen, which is the most common element on Earth. He also discovered that air contains 21 per cent oxygen and 78 per cent nitrogen (plus 1 per cent of other gases), and he later gave the element hydrogen its name.

Lavoisier was determined to find out the truth about phlogiston and combustion. In a series of brilliant experiments, he showed that combustion was due to the combination of a combustible substance (such as carbon) with oxygen, and that this forms gases of the substance known as oxides (such as carbon dioxide). Lavoisier had proven that there was no such thing as phlogiston.

In 1784, Lavoisier and fellow French scientist Pierre Simon Laplace analysed the breath of a guinea pig to show that respiration (breathing) involved breathing in oxygen and breathing out carbon dioxide.

After further experiments, he became the first to understand that mercury and nitrogen were chemical elements, and he also realized that water was not a single element but a compound of oxygen and hydrogen. Lavoisier also worked for the government as Commissioner of the Royal Gunpowder Administration. While living in the arsenal (a weapons store) in Paris, he and his wife improved the quality of the army’s gunpowder.

FURTHER DISCOVERIES

Lavoisier developed the law of conservation of mass or matter, which states that in a chemical reaction the total mass or matter of the compounds remains constant. This is a very important law of chemistry.

In 1787, Lavoisier worked with three French colleagues—Guyton de Morveau, Claude Louis Berthollet and Antoine François de Fourcroy—to produce the textbook called Méthode de Nomenclature Chimique (Method of Chemical Nomenclature). This introduced the system of chemical names that we use today. Two years later, in Traité Élémentaire de Chimie (Elementary Treatise on Chemistry), he began to list all the known chemical elements that were now the building blocks of the new science called chemistry. Along with other chemists, he also helped launch the first ever chemistry journal, which he called Annales de Chimie (Annals of Chemistry).

A TRAGIC END

In 1789 the French Revolution began. Although Lavoisier was at first supportive of its aims of overthrowing the monarchy, he was later imprisoned, together with unpopular tax collectors. On May 8, 1794, Lavoisier was tried, condemned and executed by guillotine.

Lavoisier was the greatest French scientist of his age. His work and vigorous experimentation had created a revolution in chemistry, and it was now a science in its own right.