Guillaume François Rouelle (1703-1770) was a French chemist and apothecary. In 1754 he introduced the concept of a base into chemistry, as a substance which reacts with an acid to give it solid form (as a salt). He is known as l'Aîné (the elder) to distinguish him from his younger brother, Hilaire Rouelle, who was also a chemist and known as the discoverer of urea. He started a public course in his laboratory in 1738 where he taught many students among whom were Denis Diderot, Antoine-Laurent de Lavoisier and Antoine-Augustin Parmentier.
