Defined by the equation: \[k_{\text{d}}=\frac{I_{\text{l}}}{n\ F\ c\ A}\] where the @[email protected] \(I_{\text{l}}\) is assumed to be due to the @[email protected] species of concentration \(c\) and of @[email protected] \(D\). \(n\) is the @[email protected] written so that the @[email protected] @[email protected] of this species is unity. \(A\) is usually taken as the geometric area of the electrode, and \(F\) is the @[email protected]