Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
Amedeo Avogadro (1776-1856) took Gay-Lussac's Law one step further. He stated one of the basic concepts of modern chemistry in his Law, that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. The very small print and the crowded text on this Italian commemorative may suggest a large (Avogadro's) number of molecules confined to some small space.