Gay-Lussac's law gases and the gaseous products can be expressed in simple whole numbers. For example, Gay-Lussac found that 2 volumes of hydrogen and 1 volume of oxygen would react to form 2 volumes of gaseous water. Based on Gay-Lussac's results, Amedeo Avogadro theorized that, at the same temperature and pressure, equal volumes of gas contain equal numbers of molecules (Avogadro's law). This hypothesis meant that the previously stated result could also be expressed as The law of combining gases was made public by Joseph Louis Gay-Lussac in 1808. Avogadro's hypothesis, however, was not initially accepted by chemists until the Italian chemist
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