Stanislao Cannizzaro in Italy. He is best known for his contribution to the then-existing debate over atoms, molecules, and atomic weights. He championed Amedeo Avogadro's notion that equal volumes of gas at the same pressure and temperature held equal numbers of molecules or atoms, and the notion that equal volumes of gas could be used to calculate atomic weights. In so doing, Cannizzaro provided a new understanding of chemistry. Stanislao Cannizzaro Stanislao Cannizzaro FRS (13 July 1826 – 10 May 1910) was an Italian chemist. He is remembered today largely for the Cannizzaro reaction and for his influential role in the atomic-weight
History of molecular theory contain the same number of molecules". This law implies that the relationship occurring between the weights of same volumes of different gases, at the same temperature and pressure, corresponds to the relationship between respective molecular weights. Hence, relative molecular masses could now be calculated from the masses of gas samples. Avogadro developed this hypothesis in order to reconcile Joseph Louis Gay-Lussac's 1808 law on volumes and combining gases with Dalton's 1803 atomic theory. The greatest difficulty Avogadro had to resolve was the huge confusion at that time regarding atoms and molecules—one of the most important contributions of Avogadro's work was