Antoine Lavoisier and his contribution to Chemistry

The French Bourgeoisie helping out with science:

“In performing experiments, it is necessary… that they be simplified as much as possible, and that every circumstance that could complicate the results should be completely removed.” -Antoine Lavoisier

Early life and Work:

On the 26 of  August 1743, Antoine Lavoisier was born to a wealthy family of nobility and was the son of an attorney at the Parliament of Paris. He  went to school at the College des Quatres Nations, University of Paris at the age of 11 were he studied chemistry, botany, astronomy and mathematics and received a law degree which admitted him the bar. (1).

This French nobleman, chemist and biologist is credited for being the first one to put an extensive lists of the elements, helping construct the metric system and reform chemical nomenclature. Lavoisier is also known as the “ father of modern chemistry” (1).

Lavoisier who was originally part of the Ferme generale ( most hated components of the French Ancien Regime) because of the profits it took at the expense of the state while gathering taxes and using violence with the civilians, had an influence in both the economical, political and scientific world of France.

Lavoisier's combustion apparatus

Oxygen and Combustion:  In 1772 the scientific world didn’t understand the process of burning. The theories proposed were inconsistent and conflicting with each other ,but, the main theory believed during that time was the theory of phlogiston, an undetectable substance that often had a negative mass.

Due to research that has been made, we are aware that combustion occurs when substances react with oxygen at high temperatures. However, in 1772 that wasn’t a theory that was known, but Lavoisier began working on this field which led to the discovery of oxygen two years later.

Oxygen was named in 1779 after an experiment  using sulfur and phosphorus. In that experiment, he burned those elements and realized the product produced was acidic, what he noticed was that the product weighed more than the original reactant, meaning that an element reacted with the reactants to increase the weight of the products. In 1774, Joseph Priestley visited Lavoisier to discuss an experiment were a gas was produced (which we now know as mercury oxide) and it supported combustion more than “normal air”. Use to the unusual properties of this gas, he named it dephologiscated air due to the absence of phlogiston. Lavoisier didn’t believe in that theory and found that oxygen made up 20% of air and was vital to combustion and respiration.

Forms of Carbon: In 1772 Lavoisier and other chemists bought a diamond and placed it in a closed jar where they used a giant magnifying glass to focus the sun’s rays on the diamond. The diamond burned and then disappeared. Lavoisier noticed that the weight of the jar didn’t change even though the diamond had disappeared. This observation was used as an evidence for him to be convinced that the law of conservation of mass was correct.  Lavoisier realized that the charcoal that was later burned were 2 different forms of the same element and named the element carbon.

Sulfur is an element: In 1777 Lavoisier correctly identified Sulfur as an element. He discovered sulfur after undergoing countless experiment with it and discovered it couldn’t be broken down into any other substances.

The conservation of Mass:  In 1778, Lavoisier found that when Mercury oxide is heated its weight decreases; the oxygen gas that was released has the exact weight of the missing mass in mercury oxide. Even though this seems as an obvious theory to us today, it was a discovery in 1778! After carrying numerous experiments with different compounds, Lavoisier announced the law of conservation of Mass:

-The total mass of a chemical reaction’s product is identical to the total mass of the starting chemicals  ( matter is conserved in chemical reactions)

Combustion and Respiration:  Lavoisier thought that combustion and respiration where chemically the same. He was able to demonstrate his theory with the help of Pierre-Simon Laplace, they were able to measure the amount of carbon dioxide and heat given off by a guinea pig while it breathed. They compared this data to the amount of of heat produced when they burned carbon to produce the same amount of carbon dioxide exhaled by the guinea pig.

This data allowed Lavoisier to conclude that respiration is a form of combustion, the heat produced by mammals during respiration help keep their bodies above room temperature.

Lavoisier measuring the oxygen in the air exhaled from a man’s lungs. Marie-Anne, Lavoisier’s wife made notes, she helped him during his studies.

Water is not element:  In 1783, Lavoisier named an element that was recognized by Henry Cavendish in 1766;  hydrogen. Lavoisier worked with Laplace and burned hydrogen with oxygen and found that water was the product. This proved that water was not an element, but a compound made from hydrogen and oxygen.

Lavoisier’s list of elements: (2) In 1789 published Elementary Treatise on Chemistry, which was considered groundbreaking.

The Elementary Treatise on Chemistry detailed his oxygen theory of combustion which abandoned phlogiston, made a clear difference between a compound and an element. It also contained a list of elements : oxygen, nitrogen, hydrogen,sulfur, phosphorus, carbon, antimony, copper, cobalt, gold,iron, manganese, molybdenum, nickel, platinum,silver, tungsten and zinc.

Due to the knowledge proposed at that time he also proposed light as an element.

The metric System: In 1791, Lavoisier served on a committee of the French Academy of Sciences which developed the metric system  of measurement.

Sadly Antoine Lavoisier was guillotined at the age of 50 on May 8, 1794 in Paris. The French government saw the importance of his worked and innocent him from all his charges in 1795.

Bibliography:

1. Deffree, Suzanne. “Father of Modern Chemistry Lavoisier Is Falsely Convicted, May 8, 1794.” EDN, 2018, www.edn.com/electronics-blogs/edn-moments/4413675/Father-of-modern-chemistry-Antoine-Lavoisier-is-falsely-convicted--May-8--1794.
2. “Home.” Famous Scientists, www.famousscientists.org/antoine-lavoisier/.