Electrolysis is a chemical reaction caused by passing a direct current (DC) through an electrolyte – a compound which contains ions when molten or in solution. This results in positive ions migrating to the negative electrode (cathode) and negative ions migrating to the positive electrode (anode). The type of electron transfer reaction occurring depends on the electrode potentials of the ions present, and the electrode material may also play a part in the reaction. For example, in the electrolysis of copper salts with a copper anode, atoms of the electrode ionize and enter into solution.
At each electrode the ions are discharged according to Faraday's laws:
1. The quantity of a substance produced is proportional to the amount
of electricity passed.
2. The relative quantities of different substances produce are proportional to their equivalent weights.
Hence one gram-equivalent of any substance is produced by the same amount of electricity, known as a faraday (96,500 coulombs).
Electrolysis is used to extract electropositive metals, such as sodium, magnesium, and aluminum from their ores, and to refine less electropositive metals; to produce sodium hydroxide (see sodium, chlorine, hydrogen, oxygen, and many other substances.