Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto, Count of Quaregna and Cerreto (9 August 1776, Turin, Piedmont – 9 July 1856) was an Italian scientist. He is most noted for his contributions to molecular theory, including what is known as Avogadro’s law. In tribute to him, the number of elementary entities (atoms, molecules, ions or other particles) in 1 mole of a substance, 6.02214179(30)×1023, is known as the Avogadro constant.
Amedeo Carlo Avogadro was born in Turin, Italy in 1776 to a noble family of Piedmont, Italy.
He graduated in ecclesiastical law at the early age of 21 and began to practice. Soon after, he dedicated himself to physics and mathematics (then called positive philosophy), and in 1809 started teaching them at a liceo (high school) in Vercelli, where his family had property.
In 1811, he published an article with the title Essai d’une manière de déterminer les masses relatives des molécules élémentaires des corps, et les proportions selon lesquelles elles entrent dans ces combinaisons (“Essay on Determining the Relative Masses of the Elementary Molecules of Bodies and the Proportions by Which They Enter These Combinations”), which contains Avogadro’s hypothesis. Avogadro submitted this essay to a French journal, Jean-Claude Delamétherie’s Journal de Physique, de Chimie et d’Histoire naturelle (Journal of Physics, Chemistry and Natural History) so it was written in French, not Italian. (Note: France effectively controlled northern Italy from 1796 to 1814.)
In 1820, he became professor of physics at the University of Turin. After the downfall of the French Emperor Napoléon in 1815, Piedmont again came under the control of the King of Piedmont-Sardinia, ruling from Turin.
Avogadro was active in the revolutionary movements of 1821 against King Victor Emmanuel I. As a result, he lost his chair in 1823 (or, as the university officially declared, it was “very glad to allow this interesting scientist to take a rest from heavy teaching duties, in order to be able to give better attention to his researches”).
Eventually, King Charles Albert granted a Constitution (Statuto Albertino) in 1848. Well before this, Avogadro had been recalled to the university in Turin in 1833, where he taught for another twenty years.
Little is known about Avogadro’s private life, which appears to have been sober and religious. He married Felicita Mazzé and had six children.
Some historians suggest that he sponsored some Sardinian revolutionaries, who were stopped by the announcement of Charles Albert’s constitution.
Avogadro held posts dealing with statistics, meteorology, and weights and measures (he introduced the metric system into Piedmont) and was a member of the Royal Superior Council on Public Instruction.
In honor of Avogadro’s contributions to molecular theory, the number of molecules in one mole was named Avogadro’s number, NA or “Avogadro’s constant”. It is approximately 6.0221415 × 1023. Avogadro’s number is used to compute the results of chemical reactions. It allows chemists to determine amounts of substances produced in a given reaction to a great degree of accuracy.
Johann Josef Loschmidt first calculated the value of Avogadro’s number, often referred to as the Loschmidt number in German-speaking countries (Loschmidt constant now has another meaning). Via Amedeo Avogadro