AMEDEO AVOGADRO: BIOGRAPHY AND CONTRIBUTIONS - HISTORY - 2025

Amedeo Avogadro (1776-1856) was a renowned chemist and physicist of Italian nationality, who also studied in the area of ​​law and was a professor at the University of Turin, founded in 1404. He belonged to the nobility, since he was count of the Italian towns of Quaregna and Cerreto, belonging to the province of Biella.

His most notable contribution in the scientific field is Avogadro's Law; however, he also carried out other investigations framed in atomic theory. Likewise, as a decoration for his scientific work, his surname was placed on the well-known constant -or number- of Avogadro.

In order to carry out the hypothesis known as Avogadro's law, Amedeo had to rely on other very important atomic theories, such as those of John Dalton and Gay-Lussac.

Through this, Avogadro was able to discover that equal volumes, even if they are of different gases, will contain the same number of molecules if they are subjected to the same conditions of temperature and pressure.

This law was published on July 14, 1811 under the title of Essay for a way to determine the relative masses of elementary molecules of bodies, and the proportions according to which they enter into these combinations. In this text, Amedeo emphasized the difference between atoms and molecules, which then caused confusion.

Another of his most notable works was Memory on the relative masses of the molecules of simple bodies, or expected densities of their gas, and on the constitution of some of their compounds, to later serve as an essay on the same subject, which was published in 1814. In this work he describes in detail the consistency of gases.

Biography

Lorenzo Romano Amedeo Carlo Avogadro was born on August 9, 1776 in the city of Turin. This city was known to be an important cultural center where successful businesses were also carried out.

His father was a magistrate from an ancient and noble family in the Piedmont region. Following in his footsteps, in 1796 Amedeo decided to graduate in canon law, the branch of law that is responsible for the legal regulation of the Church.

Despite this, Avogadro's true interest was in the world of mathematics and physics, so he later joined this field and dedicated his life to the field of science, generating contributions of a transcendent nature.

Scientific and teaching work

In 1809 he managed to obtain a position to teach physics classes at an institution known as the Royal College of Vercelli, which was located in an Italian city that is part of the Piedmont region.

Later, after having published his two most important texts in 1811 and 1814, in 1820 the University of Turin created a chair in physics especially to be taught by him.

This position was held by Amedeo for 36 years, until the day of his death. The dedication that this scientist had to teaching speaks of his interest in imparting knowledge, as well as the value he placed on the field of research.

A year later he published another of his emblematic texts, which he entitled New considerations on the theory of proportions determined in combinations, and on the determination of the masses of the molecules of the bodies.

That same year he also wrote Memory on how to include organic compounds in the ordinary laws of determined proportions.

During 1821 Avogadro maintained a prudent political participation during the revolution against the king of Sardinia.

However, this political interest of Amedeo was diminishing until 1848, when Alberto of Sardinia approved a modernized Constitution. In 1841, in the midst of this context, the scientist published all his works in four volumes.

Private life and death

Little is known about his personal life except that he was known to lead a sober and pious existence. He married Felicita Mazzé, with whom he had a total of six children.

It is said that he financed some revolutionaries against Sardinia; however, there is no evidence to confirm this action.

Amedeo Avogadro died on July 9, 1856 in the city of Turin at the age of 79. In his honor there is a lunar crater and an asteroid named after him.

Historical context: the atom before and during the 19th century

Origin of the term and first statements

The word "atom" is very old, since it comes from a Greek terminology that means "without parts". This implies that the affirmation of the existence of indivisible particles that make up the parts of everything that surrounds us, has been in force since long before the positioning of science as a discipline.

Despite this, the theories of Leucippus and Democritus cannot be considered to have been precursors of atomic science, since these studies respond to a very limited framework of science corresponding to the vital time of their creators.

Furthermore, these Greek philosophers did not create a scientific theory as is done today, but rather developed a philosophy.

However, these thinkers brought to the West the idea that there are homogeneous, impenetrable and invariable particles that move in a vacuum and whose properties constitute the plurality of things.

17th and 18th centuries

Thanks to the appearance of the mechanistic philosophy, during the seventeenth century different explanations were accepted that proposed the existence of microscopic particles or corpuscles, which had mechanical properties that could explain the macroscopic properties of substances.

However, the scientists who espoused these theories had to face the imminent difficulty that the relationship between the hypotheses and the data obtained within the chemistry laboratories was not achieved. This was one of the main causes of the abandonment of these precepts.

In the 18th century, chemical transformations were interpreted through the use of the precepts of constituent molecules and constituent molecules. One of the precursors of these notions was Antoine Fourcroy, who established that bodies were made up of a considerable number of molecules meeting.

For this author, the integrating molecules were united by the "force of aggregation". Therefore, each of these molecules has the characteristic of being formed in turn by the meeting of several other constituent molecules; these corresponded to the elements that made up the compound.

John Dalton's influence on Avogadro

John Dalton's studies were a fundamental piece for Amedeo Avogadro's conclusions. Dalton's most important contribution to the world of science was to direct attention to the relative weight of those particles that make up bodies. That is, his contribution was to establish the importance of atomic weights.

Consequently, the calculation of atomic weights became a very interesting tool for integrating the different laws that were in vogue at the end of the 18th century and the beginning of the 19th century. This means that the ideas of John Dalton allowed the opening for other paths within the field of science.

For example, by calculating atomic weight, the scientist Benjamin Richter implemented the notions of the law of reciprocal proportions, while Louis Proust established the law of definite proportions. John Dalton himself, through his discovery, was able to create the law of multiple proportions.

Welcome your research and your hypothesis

When Amedeo published his theories, the scientific community was not very interested, so his discoveries were not immediately accepted. Three years later, André-Marie Ampere obtained the same results despite applying a different method; however, his theories were received with the same apathy.

For the scientific community to begin to realize these findings, it had to wait until the arrival of the works of Williamson, Laurent and Gerhardt.

Using organic molecules, they established that Avogadro's law is necessary and elementary to explain the reason why equal amounts of molecules can occupy the same volume in the gaseous state.

Canizzaro's contribution

However, the definitive solution was found by scientist Stanislao Cannizzaro. After the death of Amedeo Avogadro, he managed to explain how the dissociations of the molecules worked during the heating of the same.

In the same way, the kinetic theory of Clausius gases was elementary, who was able to confirm again the effectiveness of Avogadro's law.

Jacobus Henricus also had an important participation in the field of molecules, since this scientist added pertinent notions to Avogadro's work, especially those referring to dilute solutions.

Despite the fact that Amedeo Avogadro's hypothesis was not taken into account at the time of its publication, at present Avogadro's law is considered one of the most important tools within the field of chemistry and scientific discipline, for which is a concept with broad significance within these areas.

Contributions

Avogadro's law

The scientist Amedeo proposed a method to determine, in an easy and simple way, the masses belonging to the molecules of the bodies that can pass to the gaseous state and the reference number of said molecules in the combinations.

This method consists in that, if equal volumes of gases contain an equal number of particles, the relationship between the densities of these gases must be equal to the relationship between the masses of those particles.

This hypothesis was also used by Avogadro to determine the number of molecules that make up the different compounds.

One of the peculiarities that Amedeo realized was that the results of his theory were in contradiction with the conclusions reached by the scientist Dalton, taking into account his rules of maximum simplicity.

Avogadro established that these rules were based on assumptions of an arbitrary nature, so they should be replaced by his own conclusions through the calculation of atomic weights.

Ideal gases

This Avogadro theory is part of the set of laws relating to and applicable to ideal gases, which consist of a type of gas composed of a set of point particles that move randomly and do not interact with each other.

For example, Amedeo applied this hypothesis to hydrogen chloride, water, and ammonia. In the case of hydrogen chloride, it was found that a volume of hydrogen reacts when contacted with a volume of dichlor, resulting in two volumes of hydrogen chloride.

Clarification regarding molecules and atoms

At that time there was no clear distinction between the words "atom" and "molecule". In fact, one of Avogadro's admired scientists, Dalton, tended to confuse these concepts.

The reason for the confusion of both terms was due to the fact that Dalton considered gaseous elements such as oxygen and hydrogen to be part of simple atoms, which contradicted the theory of some Gay-Lussac experiments.

Amedeo Avogadro managed to clarify this confusion, since he implemented the notion that these gases are made up of molecules that have a pair of atoms. Using Avogadro's law, the relative weight of atoms and molecules can be determined, which implied their differentiation.

Although this hypothesis implied a great discovery, it was overlooked by the scientific community until 1858, with the arrival of the Cannizzaro tests.

Thanks to Avogadro's law, the concept of the “mole” could be introduced, which consists of the mass in grams that is equal to the molecular weight. The number of molecules contained in a mole was called Avogadro's number, which is 6.03214179 x 1023 mol.l-1, this number being the most accurate at present.

References

1. Avogadro, A. (1811) Essay on a Manner of Determining the Relative Masses of the Elementary Molecules of Bodies, and the Proportions in Which They Enter into These Compounds. Retrieved on November 18, 2018 from Chem departments: chem.elte.hu
2. Bello, R. (2003) History and epistemology of science. The history of science in textbooks: Avogadro's hypothesis. Retrieved on November 18, 2018 from CSIC: uv.es
3. Heurema, (sf) Amedeo Avogadro. Retrieved on Nov 18. of 18 Heurema characters: heurema.com.
4. Tamir, A. (1990) Avogadro's Law. Retrieved on November 18, 2018 from the Department of Chemical Engineering: rua.ua.es
5. Avogadro's Law. Retrieved on November 18, 2018 from Wikipedia: wikipedia.org