The term “voltammetry “, which is dealt with in Chapter 25 of Skoog, covers several analytical methods, all of which have in common that the relationship between voltage and current during one or other electrochemical process is recorded. In the associated voltammograms, the current density is plotted against the potential of the electrode used; exemplified for the oxidation of hexacyanidoferrate(4-) to hexacyanidoferrate(3-) according to the equation \( {\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]}^{4-}\to {\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]}^{3-}+{\mathrm{e}}^{-} \) are the corresponding voltammograms for hexacyanidoferrate(4-) solutions of different concentrations as Fig. 16.14a from Harris. (The reference electrode here is a saturated calomel electrode, which we already know from ► Sect. 5.1 .) The resulting current is determined by the rate at which the ions in question diffuse to the electrode, thus effectively by their concentration in the solution in question. The linear relationship between current density and concentration is shown in Fig. 16.14b. Therefore, voltammetry can also be considered a special form of electrolysis.