The scale on the pH meter is marked off so that a change of 1 pH unit equals 0.0592 volts or 59.2 millivolts. Two electrodes, generally inert metals, are placed in a solution of an electrolyte, or a molten metal salt and a current is passed through the solution or the molten salt. Anions lose e's to the anode and are oxidized. At the cathode, cations pick up electrons and are reduced.
Reduction takes place at the cathode.
The dotted line represents a membrane to keep the components separated. At the anode a yellow-green gas is formed, and at the cathode a silvery metal is formed. In the electrolysis of a molten salt, the possible half-reactions are usually limited to those involving ions from the salt. This is a less expensive, more convenient procedure. At the other electrode, there is also a complication.