For ideal performance the auxiliary electrode should be similar in surface area, as close as possible, and evenly spaced with the working electrode.
12.
This means much of the redox chemistry will occur at the points at either end of the shortest path between the working and auxiliary electrode.
13.
Here, the potential of the auxiliary electrode is usually not measured and is adjusted so as to balance the reaction occurring at the working electrode.
14.
The auxiliary electrode balances the working electrode, but in order to know how much potential it has to add or remove it relies on the reference electrode.
15.
In a two-electrode system, either a known current or potential is applied between the working and auxiliary electrodes and the other variable may be measured.
16.
If the system was open, then it would be possible for the product of that reaction to diffuse back to the auxiliary electrode and undergo the inverse redox reaction.
17.
In addition to maintaining the proper current at the working electrode, the auxiliary electrode will experience extreme potentials often oxidizing or reducing the solvent or electrolyte to balance the current.
18.
When a three electrode cell is used to perform electroanalytical chemistry, the auxiliary electrode, along with the working electrode, provides circuit over which current is either applied or measured.
19.
A bulk electrolysis is best performed in a three part cell in which both the auxiliary electrode and reference electrode have their own cell which connects to the cell containing the working electrode.
20.
At the auxiliary electrode, this greater current would decompose a significant amount of the solution / electrolyte and probably boiling the solution in the process all in an effort to balance the current.
