Defined by the equation: \[k_{\text{d}}=\frac{I_{\text{l}}}{n\ F\ c\ A}\] where the @L03532@ \(I_{\text{l}}\) is assumed to be due to the @D01716@ species of concentration \(c\) and of @D01719@ \(D\). \(n\) is the @C00995@ written so that the @S06021@ @C01124@ of this species is unity. \(A\) is usually taken as the geometric area of the electrode, and \(F\) is the @F02325@.