Antoine Laurent Lavoisier

1743-1794

French Chemist (social reformer and lawyer, and civil servant)

B. Paris

Antoine Lavoisier (1743-1794), a member of the lesser nobility in France, used his training in law, the sciences and a keen business sense particularly with regard to accounting, to oversee the gunpowder works at the National Arsenal. This was more than just a trivial government post. The quality of gunpowder in 1775 was a matter of national security for the French who were at war with the British and about to enter the American Revolution. Lavoisier brought all of his skill to bear on the problem and soon the Arsenal was producing the highest quality gunpowder in the world.

Lavoisier had used a large portion of his inheritance to purchase the finest chemical instruments in the world and had made significant contributions to the field of chemistry before his appointment to the Gunpowder Commission. His position and experience at the Arsenal spurred his interest in combustion. His methods confirmed for him that the total amount of matter that entered a reaction also ended up as its products. Thus, there was no net change in weight when considering all of the reactants. This Law of the Conservation of Matter was not new with Lavoisier. Indeed, the ancient Greeks had formulated the law. However, Lavoisier's adherence to the law of the conservation of matter caused him to stress: the experimental method, the method of equation, and the methods of analysis and synthesis. His work led him to reject the prevailing views of the day, and in 1789 (the same year as the French Revolution) to produce a revolutionary document of his own, Elements of Chemistry. With this book Lavoisier outlined the foundation and nature of what chemistry was to become in the 19^th century.

In 1774, Joseph Priestley visited Lavoisier in Paris and described the methods by which he had collected dephlogisticated air. Lavoisier saw the importance of the discovery almost immediately and repeated the experiments that Priestley had performed. He noticed that as the red mercurius calcinatus weighed more than the mercury that it produced upon heating. Also, as the air recombined with the hot mercury, the resulting calx weighed more than the original mercury did by the weight of the collected gas. Lavoisier, who wished to save the law of the conservation of matter leapt at the solution that the mercury and the dephlogisticated air were different elements and they combined to form the calx of mercury. He called the element oxygen or acid maker.

A comparison between the Phlogiston theory and Oxygen theory of combustion.

Lavoisier soon developed a general theory of combustion that abandoned the need for phlogiston. He said that as objects burn or become calcinated, they combine with oxygen. He explained Cavendish's results with inflammable air (Lavoisier called it hydrogen or water maker) as a combination of the elements hydrogen and oxygen.

Lavoisier in his laboratory.

 Elements of Chemistry introduced his new concept of chemical element, which he defined as "the last point that analysis can reach". This he borrowed from Boyle, but Lavoisier actually demonstrated it. He listed 33 elements in the text, but some like light and heat (he called it caloric) were not material and others were compounds.

With new elements, he had to come up with a new precise way to standardize chemical names. He developed the same method that we still use today. Thus, after Elements chemistry looked modern and waited only for the advent of Dalton's atomic theory to make the transition complete.

Lavoisier wrote Elements of Chemistry in a very clear style. His wife, Marie, helped him with the text, the experiments and made the illustrations in the book. However, the book itself presented no new discoveries. Lavoisier had skillfully compiled a set of laws and methods in a way that was consonant and formed the foundation of a whole new science.

Antoine and his wife, Marie, around the time of the publication of Elements.

Priestley continued his experimental work but was forced out of Britain for his opposition to the armed intervention in the American War of Independence and for his support for the French Revolution. Indeed, his house was burned to the ground by a local mob. He moved his family to London, but did not find peace until he came to the United States to live out his last days up the Susquehanna River, just a few miles from my home.

Black was converted to the antiphlogiston science of Lavoisier. However, neither Cavendish nor Priestley ever gave up the theory of phlogiston. The Germans were equally slow in accepting the chemistry of Lavoisier but came around about a generation later.

Lavoisier did not live to see the triumph of his book. On The 8th of May 1794 Marat, his political enemy, denounced him. Lavoisier was charged with treason and sentenced to the guillotine. Perhaps the only true charge in the list of indictments was that he had been a tax collector under the old regime. His friend, Joseph Lagrange (1794) said, "It required only a moment to sever his head, and probably 100 years will not produce another like it."  Thus, the revolutionary died in a revolution, but his words lived on. The logic of Lavoisier's argument as a simpler explanation for combustion and the formation of compounds brought about the demise of the phlogiston theory. Thus, the quest for elements began and the Elements of Chemistry set the agenda for the Science of Chemistry for much of the coming century.

We think only through the medium of words. Languages are true analytical methods. -Antoine Lavoisier