The Italian physicist and chemist Lorenzo Romano Amedeo Carlo Avogadro, Conte di Quaregna e di Cerreto (1776-1856), authored the hypothesis known as Avogadro's law, which ultimately clarified the foundations of molecular chemistry and physics.

Born in Turin on Aug. 9, 1776, Amedeo Avogadro came from an ancient legal family, whose name derived from the Latin de advocatis (concerning the law). He took a degree in philosophy in 1789, a baccalaureate in jurisprudence in 1792, and a doctorate in ecclesiastical law a few years later.

After several years of legal experience, Avogadro found his true avocation in the study of the physical sciences. Though largely self-taught, he achieved an extensive knowledge of the then-expanding studies of matter in the gaseous state. In 1809 he was appointed professor of physics in the Royal College at Vercelli. Up to that time his only scientific paper had concerned a topic in the new field of electricity.

His...