Cyclic voltammetry experiments have proved very useful in;he :knowledge and understanding of the role of the potassium and hydrogen ions during the Prussian Blue reversible arrow Everitt's Salt process. While potassium ions act as a stoichiometric reactant, the hydrogen ions play a very important role in the kinetics of the electron-hopping process. The entropy change for the reaction PB reversible arrow ES has proved to be dependent on the degree of crystallinity of the him, indicating that this entropy change is related to the fixation of inner counterions on the crystal structure of the films.