It is believed that the famous Avogadro’s number was not determined by Amadeo Avogadro. He is famous for his hypothesis which states that an equal volume of different gases at the same temperature and pressure contain the same number of particles.
Later in 1865, Loschmidt used kinetic molecular theory to determine the number of particles under the standard condition for one cubic centimeter of gas which was known as Loschmidt constant with a value of 2.686773 x 1025 m-3.
French physicist Jean Baptiste Perrin used the term Avogadro’s number for the first time while explaining Brownian motion.
The value of Avogadro’s number was obtained by dividing the charge of a mole of electrons by the charge of a single electron which is equal to 6.02214154 x 1023 particles per mole.