The electrochemistry of wet solid Berlin green (BG) containing Na+ and K+ has been studied by voltammetry and chronoamperometry. It has been found that the reactions of both electroactive systems in BG, Fe(II)/(III) cyanide complex and Fe2+/3+, are diffusion controlled. The charge diffusion coefficients in BG containing K+ are high and have been estimated as 2.2 x 10(-8) cm2s-1 and 1.1 X 10(-7) cm2s-1 under transient and steady-state conditions respectively. Evidence is provided that almost all redox sites in BG are electroactive. BG has been found to be nearly 1:1 mixed hexacyanoferrate(II)/(III).