Amedeo Avogadro

Amedeo Avogadro (Lorenzo Romano Amedeo Carlo Avogadro), is a count of Quaregna and Cerreto, a physicist and chemist Italy N (Turin, August 9th 1776 - July 9th 1856)

Origins and studies

Wire of a magistrate of Turin, Amadeo Avogadro starts by following the paternal way. It passes a license of right in 1795 and is registered with the bar of its birthplace. But its taste for physics and mathematics, in which it did not cease being interested as a recluse, pushes it to start on late scientific studies. In 1809, it makes a communication with the royal Academy of Turin; the success which it gains thanks to it makes it possible him to obtain a post of professor with the royal College of Verceil. In 1820, the University of Turin creates for him a pulpit of physics which it will keep until the end of its life.

Work

In 1811, there states the assumption remained famous under the name of Loi of Avogadro. Resting on the atomic Theory, the Law of Dalton and the Law of Gay-Lussac on the voluminal reports/ratios, he discovers that two equal volumes of different gases, under the same conditions of temperature and pressure, contain an identical number of molecules. Thus, it becomes possible to determine the molar Masse of a gas from that of another. It sends the report in which it develops this theory with the Journal of Physics, Chemistry and Natural history which publishes it on July 14th, 1811 under the title Essai in a manner of determining the relative masses of the elementary molecules of the bodies, and the proportions according to which they enter these combinations . The most important difficulty that it must surmount relates to the confusion made at that time between Atome S and Molécule S. One of its most important contributions is to clearly make the distinction between the two by admitting that the molecules can be made up of atoms (distinction that does not make John Dalton, for example). Actually, it does not use the word atom in its work (at the time the terms atom and molecule is used in manner indistinct), but it considers that there exist three kinds of molecules, of which one is a elementary molecule (atom). It also carries out a distinction between the terms of Masse and Poids.

In 1814, it publishes a Mémoire on the relative masses of the molecules of the elements, or supposed densities of their gas, and on the constitution of some of their compounds, to serve as following the Test on the same subject, published in the Newspaper of Physics, July 1811 which is interested in the Densité Gaz.

In 1820, the Université of Turin creates for him a pulpit of physics which it will occupy until its death. In 1821, it publishes another report entitled Nouvelles considerations on the theory of the proportions determined in the combinations, and on the determination of the masses of the molecules of the bodies and shortly after Mémoire on the manner of bringing back the organic compounds to the ordinary laws of the given proportions .

It takes share with a careful enthusiasm with the movements of political revolution of 1821 directed against the king of Sardinia, which is worth to him to lose its station in Turin later 2 years. The official declaration of the university justifying this setting with the variation stipulates that the university is “very happy to make it possible this scientist to take some rest of its constraining activities of teaching so that it can be devoted fully to his research”. However, its political insulation decrease gradually with the interest carried to the revolutionary ideas by the kings of Savoy, interest which culminates in 1848 when Charles-Albert of Sardinia grants a modern constitution. Well before that in 1833, Avogadro can take again its station at the university of Turin because of interest carried to its scientific work.

In 1841, it completes and publishes its work in four volumes under the title Fisica dei corpi ponderabili, ossia Trattato beyond costituzione materiale de' corpi .

One knows few things with regard to his private life and his political activities. In spite of a not very flattering physique, it was known like a lady-killer, although carrying out a sober and pious life. He married Felicita Mazzé with which he had six children. Some historical studies would confirm the fact that it would have financed and helped of the revolutionists of Sardinia organizing a revolution in the island, finally stopped following the concessions of Charles-Albert. However doubts remain as for its activities because of the little of evidence.

Reactions of the scientific community

The scientific community did not hold an enthusiastic reception with its theories, and its assumptions were not accepted immediately. Three years after him, Andre-Marie Ampère obtained the same results by other methods ( On the determination of the proportions in which the bodies combine according to the number and the respective provision of the molecules whose their integral particles are made up ) but its theories was accommodated with the same indifference. It was necessary to await work of Gerhardt, Laurent and Williamson on the organic molecules to show that the law of Avogadro was essential to explain why molecules in equal quantity occupied same volume in a gas state.

However in these experiments, certain substances seemed to make exception to the rule. The solution was found by Stanislao Cannizzaro which explained during a congress in 1860 (4 years after the death of Avogadro) why these exceptions were explained by dissociations of the molecules during the heating.

With its kinetic theory of gases, Rudolf Clausius could provide a new confirmation of the law of Avogadro. A little later Jacobus Henricus van' T Hoff brought the last confirmation to the theory thanks to its work on the diluted solutions.

The name of Avogadro remains related to that of the Nombre of Avogadro indicating the number of Molécule S contained in only one mole.

Bibiography

Work of Avogadro on Gallica (French and Italian)
Mr. Morselli, Amedeo Avogadro, has Scientific Biography , ED D. Reidel 1984, ISBN 9027716242

See too

External bonds

Works of Avogadro digitized by the SCD of the University Louis Pasteur of Strasbourg.

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