Avogadro
Name: Amedeo Avogadro
Nickname/Alias: Conte de Quaregna
Achievements: One of the founders of physical chemistry.
Born: August 9, 1776; Turin, Italy
Died: July 9, 1856; Turin, Italy (Aged 79)
Field & Discipline: Chemistry
Language: Italian
Father: Count Filippo Avogadro
Mother: Anna Maria Vercellone
Siblings: Felice; Lorenzo; Luigi
Spouse: Felicita Mazzia (m. 1815)
Children: 7 children
Education: Grammar school, Turin; University of Turin (1792-97)
Major Work:
“Essai d'une maniere de determiner les masses relatives des molecules elementaires des corps . . .” (1811)
Life & Times:
In 1792, Avogadro entered the Faculty of Law of the University of Turin, where he spent the next three years, receiving a degree in jurisprudence in 1795 and the title of Doctor of Canon Law the following year.
In 1800, Avogadro had begun to take private lessons in mathematics and physics. He made impressive progress and decided to make the natural sciences his vocation. He was possibly inspired by the recent discoveries by his compatriot [inspired by] Volta*, since the first scientific research he undertook, in 1803, together with his brother Felice, was into electricity.
In 1806, at the time his first essay on electricity was published in France, Avogadro left his administrative position with the government to begin a teaching career. His first job was as demonstrator at the “Collegio delle Province”, a boarding school attached to the University of Turin. Then, on 7th October 1809, Avogadro became professor of natural philosophy (mathematics and physics,) at the College of Vercelli, where he spent the next eleven years.
In 1809, [published by] De la Mettrie* published, in the “Journal de Physique”, a six-page paper by Avogadro on the concepts of alkalinity and acidity, and then in July 1811, Avogadro’s most famous work appeared in the same journal, titled “A way of determining relative mass of elementary particles,” in the same issue as a long article by the great chemist [work related to] Berzelius*.
In 1809, [work related to] Gay-Lussac* had discovered that all gases, when subjected to an equal rise in temperature, expand by the same amount. In his essay of 1811, Avogadro deduced that at a given temperature all gases must therefore contain the same number of particles per unit volume.
This idea had been considered by others at the time, including [work related to] Dalton*, but then rejected, because it implied the concept of a divisibility of elementary particles which appeared to make no sense.
Resorting to what has been called “Avogadro's Hypothesis”, he proposed the existence of two orders of particles at the elementary level, these being atoms and molecules.
This assumption applied to both solids, when in the form of vapors and gaseous elements. From the “equal volumes, equal numbers” generalization, Avogadro offered chemists a way to determine the relative weights of the elements and their compounds, regardless of their physical state and chemical composition.
No previous scientist had made this distinction between the atoms of a substance and its molecules. Using his hypothesis, Avogadro explained the simple combining ratios of gases found by Gay-Lussac, by showing that under the same physical conditions, equal volumes of gases contained the same number of particles. It had already been seen that the electrolysis of water, to form hydrogen and oxygen, produced twice as much hydrogen, by volume, as oxygen.
Avogadro reckoned that each molecule of water must contain hydrogen and oxygen atoms in the proportion of 2 to 1.
Also, because the oxygen collected weighed 8 times as much as the hydrogen, the oxygen atoms present must be 16 times as heavy as the hydrogen atoms. It also followed from Avogadro's hypothesis that a molar volume of any substance, the volume whose mass is one gram of molecular weight, contains the same number of molecules. This quantity, now known as Avogadro's Number, or Constant, is equal to 6.02252 x 1023.
For Avogadro, between 1811 and his appointment at the University of Turin in 1820 was a productive scientific period, during which he published 12 essays and articles.
For the next six years Avogadro turned his attention to the study of the physical behaviour of gases and vapours. This was the beginning of twenty years of work on the problem of specific heats of bodies in their three states and on many attempts to correlate them with other physical and chemical characteristics. In the last year of his stay in Vercelli, the Royal Academy of Sciences made Avogadro a permanent member.
A few months after his appointment in Turin, Avogadro read an extensive paper to the Turin Academy of Sciences, the 160-page long Nouvelles considerations sur la theorie des proportions determinees dans les combinaisons et sur la determination des masses des molecules des corps, in which he clearly reasserted the “equal volumes, equal numbers” generalization, stressing its superiority over the use of chemical equivalents as a precise method to determine the weights of chemical elements and compounds.
Political changes of 1821 led to the suppression of his chair, along with several others, and Avogadro lost his position in 1822. After 1832, the number of Avogadro's publications declined, as he was devoting most of his time to gathering material for the preparation of his most extensive work, the four-volume “The Physics of Heavy Bodies”, published between 1837 and 1841.
This treatise was devoted to the study of the constitution of heavy ordinary bodies, the nature of molecules, the nature of molecular forces and how physical states could be interpreted in terms of these forces.
In the early 1840s, Avogadro turned his attention to two totally unrelated fields of research. The first resulted in a mathematical analysis of the dielectric, published in 1844 and the second on a clearer method for classifying and designating chemical compounds.
In the last years of his scientific career Avogadro turned to the study of atomic volumes. Between 1846 and 1852, he published four articles on the subject in the “Memoires” of the Academy of Turin.
An 1853 paper to the Royal Academy of Sciences of Turin (the last of Avogadro's many contributions) was a 70-page analysis of Regnault*'s recent series of observations on the behaviour of gases subject to different degrees of compression.
Avogadro died in Turin.
Two years after his death, his fellow Italian [work related to] Cannizzaro* showed how the application of Avogadro's hypothesis could solve many of the major problems in chemistry. At the Karlsruhe Chemical Congress of 1860, Avogadro's 1811 paper was read again to a much wider and more receptive audience of distinguished scientists.
Extra Connections: His work related to that of [work related to] Berthollet*
Assessment: Principally remembered for the hypothesis, subsequently known as Avogadro's Law, stating that, at a given temperature, equal volumes of all gases contain the same number of molecules.
Oneliner: Amedeo Avogadro, chemist and discoverer of Avogadro’s number
Bibliography:
- Abbot, David (ed.), The Biographical Dictionary of Chemists', Blond Educational: London, 1983.
- Morselli, Mario, Amedeo Avogadro, Dordrecht & Boston: D. Reidel Publishing Co., 1984.