I have been searching for about 3 days how Avogadro's constant is found, and as all of us know the value is determined by division of charge of one mole of electrons (Faraday's constant) by the charge of one electron. What confuses me is that, Faraday's constant is 96500 (it's not accurate value) and its unit is C/mole. If the mole is defined by Avogadro's Constant and Avogadro used Faraday's constant to determine his constant, what was the definition of mole for Faraday?

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    $\begingroup$ did you look here? en.wikipedia.org/wiki/Avogadro_constant#History Not sure what you're really trying to figure out. It would take a book to discuss how weight/mass and the understanding of atoms developed scientifically. It wasn't a direct line of thought. $\endgroup$
    – MaxW
    Apr 15, 2020 at 21:47
  • $\begingroup$ A gram equivalent times the stoichiometric coefficient contains the same amount of substance as a mole. To define the mole, you don’t need Avogadro’s constant, just atomic weights and a balance. $\endgroup$
    – Karsten
    Apr 16, 2020 at 0:32

1 Answer 1


These constants have been named in honour of these people. They did not even know the existence of mole concept.

In order to search how early precursors to Avogadro's number's were found, read about Loschmidt constant and then move to Avogadro's story. There were many $independent$ methods to determine Avogadro's constant. Loschmidt was trying to estimate size of the "air molecule" in 1865. Number of particles in air in a given volume.

The determination of Faraday's constant does not require the knowledge of Avogadro' ideas or his laws. This is a modern misconception. However, it does require the concept of gram equivalents (precursors to atomic mass or formula weights). In Faraday's time, measuring current/voltage and masses of substances was not a big deal. By electrolyzing a solution of silver salt, you can deposit a known mass of silver on the electrode. I am showing a page how Faraday's constant was found. As you can see we never needed to invoke Avogadro's law or numbers and constant. Faraday did such neat experiments! Clever and simple.

Electro-chemistry: General theory, Volume 1, pg 4, By Robert Alfred Lehfeldt, T. S. Moore. Longmans, Green and Company, 1904.

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