How did Avogadro count his number?
In: 241
He started at an early age because it takes a long time to count that far.
Jokes aside, Avogadro never measured or calculated the value of Avogadro’s constant. The constant was named after him more than 50 years after his death, and the first measurements of the constant were around ten years after his death. Source: [Wikipedia](https://en.wikipedia.org/wiki/Avogadro_constant#First_measurements)
Avogadro’s number is basically just the number of hydrogen atoms that weigh a gram. When scientists started to figure out that other elements are comprised of the same stuff, in discrete multiples, it becomes a useful conversion between the “atomic weight” and the actual weight.
Precisely, it’s carbon-12 that is used to define the conversion, not hydrogen.
Avogadro’s number is the number of particles (atoms or molecules) of a substance such that the atomic mass in amu’s of a single particle is equal to the mass of all the particles together in grams. Avogadro was the first to conceptualize such a number when he proposed that the pressure of a gas is directly proportional to the number of particles in that gas, but he didn’t actually calculate what it was. It was just known to exist. German physicist Josef Loschmidt was the first one to estimate the number mathematically based on the ideal gas law equation.
It was very simple, he did not do that. Amedeo Avogadro (1776–1856) proposed in 1811 that the volume of a gas at a given temperature and pressure is proportional to the number of atoms or molecules in the gas regardless of the nature of the gas. The constant that later would get his name was never measured during his lifetime.
The principle can be useful even if you do not know what number of molecules results in a specific volume. If you burn 2 H2 + O2 = 2 H20 the number of molecules is reduced to 2/3 of the original number and the volume will decrease by that amount when the pressure and temperature return to the same value.
The name of the constant was confined by Jean Perrin in 1909
This measurement was done by by Josef Loschmidt in 1865, it was technically another constant but you can calculate the avogradis constant from it. This is after Avogrado had died.
[https://en.wikipedia.org/wiki/Avogadro_constant#First_measurements](https://en.wikipedia.org/wiki/Avogadro_constant#First_measurements)
Jean Perrin determined the constant in multiple ways and got the Nobel Prize in physics in 1926 largely because of it. The award ceremony speech described in part how it was done [https://www.nobelprize.org/prizes/physics/1926/ceremony-speech/](https://www.nobelprize.org/prizes/physics/1926/ceremony-speech/)
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