LAVOISIER: BIOGRAPHY, EXPERIMENTS AND CONTRIBUTIONS - SCIENCE - 2024

Antoine-Laurent de Lavoisier (1743-1794) was a French economist, chemist and biologist, a leading figure in the chemical revolution of the 18th century. His most important contributions were the law of conservation of mass and the discovery of the role of oxygen in respiration, among others.

He also studied the water molecule, refuted the phlogiston theory, and explained combustion. In addition, he wrote an elementary text on chemistry, helped introduce the metric system, created the first periodic table, and contributed to the establishment of the nomenclature of modern chemistry.

The son of a wealthy Parisian lawyer, he completed his law studies, although his true passion was natural science. He began his studies in the field of geology, thanks to which he was proclaimed a member of the prestigious Academy of Sciences. At the same time, he developed a career as a tax collector for the Crown.

He married Marie-Anne Pierrette Paulze, who actively collaborated with Lavoisier on his scientific works, translating British chemists into French and learning art and printmaking to illustrate her husband's experiments.

In 1775, Lavoisier was appointed commissioner of the Royal Administration of Gunpowder and Saltpeter, working on improving gunpowder. He held various public offices, and, as an official of the monarchy, he was sentenced to death and executed by guillotine in Paris.

Lavoisier's science

The main principle of Antoine Lavoisier's studies is the importance he gave to carrying out the measurement of matter, in the same way that it was carried out in fields such as physics.

This conception made Lavoisier become the father of modern chemistry, basically because he was the one who introduced the quantitative field into this science and who really gave that discipline the character of science.

Within this framework, it can be said that Lavoisier made it very clear in all his actions that chance had no place in his work and studies. Chance was not conceived as something that could actively participate in his experiments.

Emphasis on matter

Matter was the element that generated the most concern, and to understand its structure and characteristics, Lavoisier concentrated on studying the four elements known until then: earth, air, water and fire.

In the midst of these dissertations, Lavoisier estimated that air had a fundamental role in combustion processes.

For Lavoisier, chemistry was more focused on the synthesis and analysis of matter. This interest was framed precisely in that quantitative notion and that corresponds to the cornerstone of this scientist's proposals.

Some authors, such as the philosopher, physicist and historian Thomas Kuhn, see Lavoisier as a revolutionary in the field of chemistry.

Descartes methodology

Antoine Lavoisier was characterized by recognizing the importance of using a rigorous method to carry out his experiments, based on understanding the context of what is being investigated.

In fact, he thought that it was necessary to structure a global plan through which the problem could be completely covered and each action established in detail, verifying what other scientists had studied.

According to Lavoisier, only after this vast verification is it possible to formulate one's own hypotheses and determine how to continue with the investigation from there. One of the quotes attributed to this character is "science does not belong to one man, but rather to the work of many."

Collaboration

Lavoisier fervently believed in the importance of collaboration among colleagues.

In fact, at one point in his life he had a laboratory equipped with the most modern tools and, in addition, he had a spacious and welcoming space ready to receive scientists who came from other cities or countries, with whom Lavoisier had communication.

For Lavoisier, working together was essential to discover what he called the secrets of nature.

Experiments

Lavoisier was characterized by being one of the first scientists to put into practice the precepts of what is now known as stoichiometry, which is about calculating how much of each element is used in a chemical reaction.

Lavoisier always focused on weighing and meticulously measuring each element that participated in a chemical reaction that he was studying, which is considered one of the most representative elements of the influence it had on the development of chemistry as a modern science.

The non-transmutation of matter

From ancient times there was a general notion in alchemists according to which it was possible to transform and create matter.

The desire to convert low-value metals such as lead into other high-value metals such as gold was always present, and this concern was based on the concept of the transmutation of matter.

Using his tireless rigor, Lavoisier wanted to experiment with this conception in mind, but making sure to measure absolutely all the elements involved in his experimentation.

He measured a specific volume and then put it in a tool, which had also been measured previously. He allowed the water to reflux for 101 days and then distilled the liquid, weighed it, and measured it. The result he obtained was that the initial measure and weight matched the final measure and weight.

The flask you used had a dusty element on the bottom. Lavoisier weighed this flask and the weight also coincided with that recorded at the beginning, which helped him to show that this powder came from the flask and did not correspond to a water transformation.

In other words, matter remains unchanged: nothing is created or transformed. Other European scientists had already made this approach, such is the case of the botanist and physician Herman Boerhaave. However, it was Lavoisier who quantitatively verified this claim.

Air and combustion

In Lavoisier's time, the so-called phlogiston theory was still in force, which made reference to a substance that bore that name and which was responsible for generating combustion in the elements.

That is, it was thought that any substance that had the predisposition to undergo combustion had phlogiston in its composition.

Lavoisier wanted to delve into this conception and was based on the experiments of the scientist Joseph Priestley. Lavoisier's finding was that he identified an air that remained uncombined after combustion - which was nitrogen - and another air that did combine. He called this last element oxygen.

The conformation of water

Likewise, Lavoisier discovered that water was an element made up of two gases: hydrogen and oxygen.

Some previous experiments by various scientists, among which the chemist and physicist Henry Cavendish stands out, had investigated this topic, but had not been conclusive.

In 1783 both Lavoisier and the mathematician and physicist Pierre-Simon Laplace carried out experiments considering the combustion of hydrogen. The result obtained, endorsed by the Academy of Sciences, was water in its purest state.

Breathing

Another area of ​​interest for Lavoisier was that of animal respiration and fermentation. According to several experiments carried out by him, which were also unusual and advanced for the time, respiration corresponds to an oxidation process very similar to that of carbon combustion.

As part of these lectures, Lavoisier and Laplace carried out an experiment in which they took a guinea pig and placed it in a glass container with oxygen for approximately 10 hours. They then measured how much carbon dioxide had been produced.

Likewise, they took as a reference a man in activity and at rest, and measured the amount of oxygen that he required at each moment.

These experiments made it possible for Lavoisier to affirm that the combustion generated from the reaction between carbon and oxygen is what generates heat in animals. In addition, he also deduced that in the middle of physical work a higher oxygen consumption is necessary.

Main contributions to science

The law of conservation of mass

Lavoisier showed that the mass of products in a chemical reaction is equal to the mass of the reactants. In other words, no mass is lost in a chemical reaction.

According to this law, mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. This is one of the most important and basic laws of modern chemistry and physics.

The nature of combustion

One of the main scientific theories of Lavoisier's time was the phlogiston theory, which stated that combustion was made up of an element called phlogiston.

Burning things were believed to release phlogiston into the air. Lavoisier refuted this theory, showing that another element, oxygen, played an important role in combustion.

Water is a compound

Lavoisier, during his experiments, discovered that water was a compound made of hydrogen and oxygen. Before this discovery, scientists throughout history had thought that water was an element.

Lavoisier reported that the water was approximately 85% oxygen and 15% hydrogen by weight. Therefore, water appeared to contain 5.6 times more oxygen by weight than hydrogen.

The elements and chemical nomenclature

Lavoisier laid the foundations of modern chemistry, incorporating a "Table of Simple Substances", the first modern list of elements then known.

He defined the element as the "last point that analysis is capable of reaching" or, in modern terms, a substance that cannot be further broken down into its components.

A large part of their system for naming chemical compounds is still in use today. In addition, he named the element hydrogen and identified sulfur as an element, observing that it could not be decomposed into simpler substances.

The first chemistry textbook

In 1789, Lavoisier wrote the Elementary Treatise on Chemistry, becoming the first chemistry book, which contained the list of elements, the most recent theories, and the laws of chemistry (including the conservation of mass), and in which it also refuted the existence of phlogiston.

The caloric theory

Lavoisier did extensive research on the theory of combustion, in which, he argued, the combustion process resulted in the release of caloric particles.

He started from the idea that in each combustion there is a detachment of the matter of heat (or igneous fluid) or of light, to later demonstrate that the "matter of heat" is weightless when verifying that the phosphor burned in the air in a closed flask, without appreciable weight change.

Animal respiration

Lavoisier discovered that an animal in a closed chamber consumed "eminently breathable air" (oxygen) and produced "calcium acid" (carbon dioxide).

Through his respiration experiments, Lavoisier invalidated the phlogiston theory and developed investigations into the chemistry of respiration. His vital experiments with guinea pigs quantified the oxygen consumed and the carbon dioxide produced by metabolism.

Using an ice calorimeter, Lavoisier showed that combustion and respiration were one and the same.

He also measured the oxygen consumed during respiration and concluded that the amount changes depending on human activities: exercise, eating, fasting, or sitting in a hot or cold room. In addition, she found variations in pulse and respiratory rate.

Contribution to the metric system

During his period on the committee of the French Academy of Sciences, Lavoisier, along with other mathematicians, contributed to the creation of the metric system of measurement, through which the uniformity of all weights and measures in France was ensured.

Contribution to the study of photosynthesis

Lavoisier showed that plants receive the material necessary for their growth from water, the earth or air, and that light, CO2 gas, water, O2 gas and energy exert a direct influence on the photosynthesis process. green part of plants.

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