In the heart of the historic centre of Vercelli, at Via Manzoni 11, the former Royal College is today a building of great architectural and cultural value. But for the international scientific community this place represents much more: it is the physical space in which Amedeo Avogadro (1776–1856) taught and developed the ideas that would lay the foundations of modern chemistry. Between 1809 and 1819, in these classrooms, Avogadro taught courses in physics and mathematics – then grouped under the denomination of “positive philosophy” – and developed the famous hypothesis on gases that bears his name, from which derive the concept of the mole and the so-called “Avogadro’s Number”.
The hypothesis formulated by Avogadro in 1811 – according to which equal volumes of gases, under the same conditions of temperature and pressure, contain the same number of particles – was a radical idea for its time, destined to remain misunderstood or underestimated for a long period. Only decades later, thanks also to the work of Stanislao Cannizzaro and to the discussions at the Karlsruhe Congress of 1860, would it be fully recognised as a foundation of atomic-molecular theory. However, its historical and conceptual roots lie precisely in Avogadro’s activity at the Royal College of Vercelli, where the everyday practice of teaching, theoretical reflection and the elaboration of a new way of thinking about matter all intersect.
In 2026, the 250th anniversary of the birth of Amedeo Avogadro and the 170th anniversary of his death will be celebrated. This double anniversary offers a particularly significant opportunity to formally acknowledge the role of the former Royal College of Vercelli in the history of chemistry: the place where Avogadro taught and developed the ideas that would lead to his 1811 hypothesis can thus become, precisely on the occasion of these symbolic dates, a visible point of reference for Europe’s scientific memory.The hypothesis formulated by Avogadro in 1811 – according to which equal volumes of gases, under the same conditions of temperature and pressure, contain the same number of particles – was a radical idea for its time, destined to remain misunderstood or underestimated for a long period. Only decades later, thanks also to the work of Stanislao Cannizzaro and to the discussions at the Karlsruhe Congress of 1860, would it be fully recognised as a foundation of atomic-molecular theory. However, its historical and conceptual roots lie precisely in Avogadro’s activity at the Royal College of Vercelli, where the everyday practice of teaching, theoretical reflection and the elaboration of a new way of thinking about matter all intersect.
The former Royal College therefore constitutes a unique place of scientific memory: it directly links a theoretical intuition of global scope – the possibility of “counting” particles through the mole – to a concrete local context, made up of classrooms, students, teaching tools and academic life. In this sense, the site is not only a point of historical interest, but a true landmark of European chemistry, where it is possible to tell how a single idea, born in a setting that was peripheral with respect to the major scientific centres of the time, contributed to unifying the language and practices of chemistry throughout Europe and the world.
