Gas dioxide, and air expand to the same extent over the same 80 kelvin interval. He noted that, for an ideal gas at constant pressure, the volume is directly proportional to its temperature: In 1802, Joseph Louis Gay-Lussac published results of similar, though more extensive experiments. Gay-Lussac credited Charles' earlier work by naming the law in his honor. Gay-Lussac himself is credited with the law describing pressure, which he found in 1809. It states that the pressure exerted on a container's sides by an ideal gas is proportional to its temperature. In 1811, Amedeo Avogadro verified that equal volumes of pure
Kinetic theory of gases "K": This is a first non-trivial result of the kinetic theory because it relates pressure, a macroscopic property, to the (translational) kinetic energy of the molecules formula_12, which is a microscopic property. Rewriting the above result for the pressure as formula_13, we may combine it with the ideal gas law where formula_14 is the Boltzmann constant and formula_15 the absolute temperature defined by the ideal gas law, to obtain which leads to simplified expression of the average kinetic energy per molecule, The kinetic energy of the system is N times that of a molecule, namely formula_18. Then the temperature formula_15