Jean Perrin, a French scientist, was one of the earlier researchers who attempted to determine the Avogadro constant.
Who inspired Perrin?
Prior to Perrin’s work in 1909, Amedeo Avogadro, an Italian scientist, published papers between 1811 and 1841 and suggested that
Equal volumes of all gases at the same temperature and pressure have the same number of molecules
This became known as Avogadro’s law. It implies that for a given mass of an ideal gas at constant temperature and pressure, the volume V of the ideal gas is directly proportional to its amount n:
V = kn (1)
where k is the proportionality constant.
When eq1 is incorporated into the combined gas law, which was developed many years earlier, we have the ideal gas law:
pV = nRT (2)
At that time, n was known as ‘amount of gas’ rather than ‘number of moles’, as the mole concept had not yet been developed. Since the amount of gas can be in measured in different ways, the gas constant R had different units back then.
Avogadro also investigated the relative mass of different gases; for example, he deduced from gas density data that the relative molecular weight of nitrogen and hydrogen is in the ratio of 13.2 : 1 and that the ratio of oxygen molecules and hydrogen molecules in water is 0.5 : 1.
Lastly, the research of botanist Robert Brown in 1872, which involved the random motion of particles suspended in a liquid or a gas due to their collisions with the surrounding molecules, also played an important role in Perrin’s calculations.
