Although Avogadro’s number is probably the best known number in chemistry, Avogadro himself knew nothing about its value or the concept of the mole. Avogadro, or to give him his full title, Lorenzo Romano Amedeo Carlo Avogadro, conte di Quaregna e di Cerreto was a lawyer with an interest in philosophy. He was born in Turin in 1776 and around the turn of the nineteenth century began private studies in science. This...