[History of chemical radicals: the part of Auguste Cahours (1813-1891)].

Auguste Cahours succeeded Dumas, as professor to Ecole centrale, and Chevreul, as examiner to Ecole polytechnique. He was connected with many french and foreign chemists. His works relating to vapour densities, radicals and organometallic compounds were conclusive for acceptance of the Avogadro's law and setting up valency by chemists about 1860.