Antoine-Laurent Lavoisier | Biography

Antoine-Laurent Lavoisier, the father of modern chemistry, was the first scientist to explain how things burn. He developed the first rational system for naming chemical compounds, which is still in use today, and established the practice of accurate measurement, which is the basis for all valid quantitative experiments.

Lavoisier grew up in Paris, France, the product of a sophisticated urban culture and a well-to-do bourgeois lifestyle. Lavoisier's mother adored her first-born, and after her premature death, he received equally doting care from his young aunt. The boy was treated to an excellent education at an exclusive school, where he proved to be a brilliant student.

Lavoisier's father was an influential attorney and the vocation of law was a family tradition. Although Lavoisier earned his law degree, he never became intrigued by the profession. Instead, he began studying with some of France's most distinguished scientists in the fields of astronomy, mathematics, botany, geology, and chemistry. By the time he embarked on his scientific career, he had gained entrance into the leading intellectual circles of the day and had been exposed to a great variety of scientific pursuits.

The breadth of Lavoisier's curiosity is reflected in his earliest research. Before he turned twenty-five, he had discovered the composition of the mineral gypsum (plaster of Paris), collaborated in producing a geological atlas of France, and explored the possibility of using street lights in France's large towns. Lavoisier was elected to France's Academy of Sciences in 1768.

Lavoisier's experiments with gypsum illustrate one of his strengths as a chemist--accurate measurement. By carefully measuring the amount of water given off when gypsum was heated, Lavoisier showed that the mineral is composed partly of water. Although a handful of earlier scientists had paid careful attention to measurement, most notably Joseph Black and Henry Cavendish, it was Lavoisier who convinced the majority of chemists that accurate measurements are essential to experimental success and scientific progress.

As a member of the scientific academy, Lavoisier served on many boards and committees that were appointed by the government to improve public welfare. He set up a model farm for applying scientific methods to agriculture; he helped standardize the national system of weights and measures, which laid the foundation for today's metric system; and he investigated prison reform and many other topics of public interest.

In 1768 Lavoisier dispelled the ancient notion that earth could be created from water. People thought this was possible because a solid sediment appears when water is heated for several days. Lavoisier conducted a long, tedious experiment to disprove this idea. By carefully weighing the glass container and the water it held before and after his test, Lavoisier proved that the sediment was made up of material that had been eaten away from the container during heating.

In 1771 Lavoisier married Marie Paulze, who was barely 14 years old. Madame Lavoisier was not only beautiful but also intelligent. She soon began to collaborate with her husband in his scientific work, translated English works into French for him, and illustrated his works. Although Lavoisier was fairly wealthy, scientists earned little money in those days, and he was forced to invest his funds in a profit-making venture in order to support his research. Unfortunately, he chose to invest in a private agency that collected taxes for the government. (Marie's father was an executive of the firm.) The French peasants viciously hated these tax collectors, who were notorious for gouging extra profits, but the money Lavoisier made from this position allowed him to continue with his scientific research. This job, however, would later contribute to his death.

During the early 1770s Lavoisier began heating substances in air to see whether they would burn. Using two huge magnifying lenses, he placed diamond in a ray of sunshine that was filtered through the lenses. The diamond slowly disappeared and carbon dioxide gas accumulated. This test proved that diamonds are made of carbon, or at least contain carbon. Lavoisier also showed that diamonds would not burn without air. Intrigued by the process of combustion, Lavoisier went on to burn other substances such as phosphorus and sulfur. Again, by carefully measuring the materials and containers, he showed that these elements gain weight when they are heated in air.

According to the accepted theory of the day, a substance called phlogiston is released during combustion. But Lavoisier realized that materials were not losing phlogiston, they were combining with a portion of the air, which increased their weight. Around the same time, Joseph Priestley had isolated a gas that greatly promoted combustion. He called it dephlogisticated air because it absorbed phlogiston so readily. Lavoisier realized that this gas was precisely the same as that part of the air which reacts with substances during combustion. After repeating and expanding Priestley's experiments, Lavoisier announced his new theory. Stating that phlogiston is required if an object is to burn, he re-named Priestley's gas oxygen and argued that air also contains a second gas, which does not support combustion. Although Lavoisier called it azote, it was soon given its modern name of nitrogen. Lavoisier's discovery additionally implied that the total weight of the substances taking part in a chemical reaction remains the same before and after the reaction. Today we call this fundamental concept the law of conservation of mass. A popular version of this law says that matter can be neither created nor destroyed.

In 1775 Lavoisier was put in charge of the government's gunpowder manufacturing operation. He and Marie moved to the arsenal, where they lived for many years. There, using his investment earnings, Lavoisier set up a magnificent private laboratory--the best in Europe at that time. One of his most valuable pieces of equipment was a chemical balance that could weigh objects with great precision. Leading scientists from France met regularly at Lavoisier's laboratory, and world-renowned figures such as Thomas Jefferson (1743-1826) and Benjamin Franklin also visited.

As an offshoot of his studies of combustion, Lavoisier began to explore the process of respiration. Working with French physicist Pierre Laplace, Lavoisier measured the heat given off when guinea pigs and sparrows digest food. These experiments, reported in 1789, showed that animals' energy and warmth depends on oxygen intake. Lavoisier and Laplace also demonstrated that nitrogen plays no part in respiration; it is only the oxygen in the air that is needed to support animal life.

As his reputation grew, Lavoisier was recruited to pursue new research avenues. Louis-Bernard Guyton de Morveau (1737-1816), a colleague who was trying to write a history of chemistry, turned to Lavoisier for help. It was Lavoisier who pinpointed the biggest problem--language. For centuries alchemists had deliberately tried to keep their discoveries secret from common people, so they gave new substances absurd names, such as butter of arsenic or sugar of lead, that were meaningless to the uninitiated. In collaboration with other chemists, including Claude Berthollot, Lavoisier developed a new, logical system for naming chemical substances in 1787. They decided that a chemical name should indicate the elements that make up the compound; for example, hydrogen sulfide contains hydrogen and sulfur.

In 1789, just two years after introducing this system, Lavoisier published the first truly modern chemical textbook, Elementary Treatise on Chemistry. In it he not only stated the law of conservation of mass, but also revived the definition of element, which had been suggested earlier by Robert Boyle, and listed all the substances thought to be elements at that time. Lavoisier emphasized that the list probably contained some compounds that could be decomposed only with advanced scientific techniques. Overall, the list was remarkably accurate.

Anxious to prove himself, Lavoisier often discredited the contributions of other chemists to his work. For example, even though Lavoisier deserves full credit for figuring out the combustion process, he neglected to mention the information he got from Priestley. Similarly, Lavoisier repeated research done by Cavendish, who discovered inflammable air and burned it to produce water. When Lavoisier named this gas hydrogen, he failed to point out that Cavendish had performed the original experiments. Possibly, these omissions were not intentional; Lavoisier simply wanted, very badly, to discover an element himself--something he would never accomplish.

With the outbreak of the French Revolution in 1789, Lavoisier's position as an administrator in the government's tax collection agency automatically made him a target of hatred. After being barred from his laboratory, Lavoisier fled his home but was caught and arrested a few months later. When he protested that he was a scientist, not a taxman, he was told: "The Republic has no need of scientists." Lavoisier was charged with ridiculous crimes. Testifying against him was an age-old enemy, Jean-Paul Marat (1743-1793), whom Lavoisier had prevented, with good reason, from joining the Academy of Sciences. Eager for revenge, Marat accused Lavoisier of diluting commercial tobacco and cutting off Paris's air supply by building a defensive wall around the city. On May 8, 1794, Lavoisier was sentenced to death and guillotined.