How Avogadro's number is determined?

Soon after Dalton's atomic theory was proposed and different atomic models were proposed, it was found that certain experimental facts regarding the chemical combination of gases couldn't be properly reconciled with his theory. Later French chemist Joseph Gay-Lussac observed that when two molecules of hydrogen gas combined with one molecule of oxygen gas it gives two molecules of water. The product forms are always in simple proportion.

After detail study of Gay-Lussac experiments, Italian physicists L.R.A. Avogadro proposed new hypothesis called Avogadro hypothesis in 1811 A.D.It was not until about 100 years after Avogadro's hypothesis had been proposed that the Avogadro number N○ could be determined accurately. There were many methods to determine the Avogadro's number. One of them is based on the principle of electrolysis. The famous British scientist Michael Faraday said in laws of electrolysis that while passing the electric current in an electrolyte the substance liberate on electrodes which depends on the current supplied . It was measured that the electricity required to liberate substance equal to equivalent weight which is called Farad(F). 

We have F = 9.64846 x 10^4 coulombs per mole. Similarly R.A. Millikan of U.S.A determine the electronic charge of an electron e = 1.6x 10^-19 coulombs. We have a relation F = N○e . Putting the value of F and e , we can get N○ = 6.02205 x 10^23 molecules.