Avogadro's law "P" are taken at standard conditions for temperature and pressure (STP), then "k"'=1/"n", where "n" is Loschmidt constant. Avogadro's hypothesis (as it was known originally) was formulated in the same spirit of earlier empirical gas laws like Boyle's law (1662), Charles's law (1787) and Gay-Lussac's law (1808). The hypothesis was first published by Amadeo Avogadro in 1811, and reconciled Dalton atomic theory with the "incompatible" idea of Joseph Louis Gay-Lussac that some gases were composite of different fundamental substances (molecules) in integer proportions. In 1814, independently from Avogadro, André-Marie Ampère published the same law with similar conclusions. As Ampère was
Gas blending total number of all molecules in the mixture. For example, a 50% oxygen, 50% helium mixture will contain approximately the same number of molecules of oxygen and helium. As both oxygen and helium approximate ideal gases at pressures below 200 bar, each will occupy the same volume at the same pressure and temperature, so they can be measured by volume at the same pressure, then mixed, or by partial pressure when decanted into the same container. The mass fraction can be calculated from the molar fraction by multiplying the molar fraction by the molecular mass for each constituent, to find