This paper develops a framework for the interpretation of ionic insertion/deinsertion reactions in an aqueous environment taking place in transition-metal hexacyanoferrates of the general formula Kh [Fe2+ (CN)6]l·mH2O, also called Prussian Blue. Three different processes were fully separated in the electrochemistry of these films. It was clearly identified that one of these electrochemical processes involves the insertion/deinsertion of H3O+ (hydrated protons) through the channels of the Kh [Fe2+ (CN)6]l·mH2O structure to reach the film electroneutrality during the electron transfer between Everitt's Salt and Prussian Blue. The other electrochemical processes involve K+ or H+ (proton) exchange through the water crystalline structure existing in the channels of the Kh [Fe2+(CN)6]l·mH2O structure.