Faraday's Law
also known as electrolysis stoichiometry
Faraday's law states that the amount of substance deposited at an electrode is proportional to the quantity of electricity passed. One mole of electrons — 96,485 coulombs — deposits one mole of a monovalent metal, or half a mole of a divalent metal such as copper or zinc. Theoretical deposition mass is therefore current multiplied by time, divided by the charge per mole and multiplied by the equivalent mass.
Why it matters in practice
It gives the theoretical ceiling against which actual electrowinning cells are judged, and it is what makes current efficiency a meaningful number rather than a comparison between plants. It also sizes the rectifier and the cell house for a target production rate.
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Reference entry GL-FARADAYS-LAW. Definitions on this page describe engineering practice in hydrometallurgical process design; they are not a substitute for test work on your own material.