1811 : Avogadro’s Essay on a Manner of Determining the Relative Masses…

Avogadro synthesized both Dalton’s and Gay-Lussac’s works to propose the hypothesis that equal volumes of gases contain an equal number of molecules within the same conditions. Though this idea accurately addresses both weight and volume simultaneously, the challenge of incorporating diatomic ideas kept it in obscurity until Canizzaro convincingly argued it at Karlsruhe in 1860.