https://doi.org/10.1351/goldbook.M03944
The value of the potential of a given electrode with respect to a suitable @R05229@ when appreciable contributions to the total anodic and/or cathodic partial currents are made by species belonging to two or more different couples, but the total current is zero, i.e. \[I=\sum _{\begin{array}{c}
i
\end{array}}I_{i}=0\qquad (I_{i}\neq 0)\] where \(I_{i}\) is the partial current of reaction \(i\) \[I_{i}=I_{i,a}+I_{i,c}\]