Studies of different hydrated forms of Prussian Blue

Abstract

Results of thermal gravimetric analysis, electrical conductivity and ¹H n.m.r. studies of Prussian Blue, Fe³⁺₄[Fe²⁺(CN)₆]₃·nH₂O, a classical mixed-valence compound exhibiting semiconducting behaviour in the temperature range 30–150 °C, are presented. Three different stages of hydration together with the anhydrous form have been identified by thermal gravimetric analysis. The proton magnetic resonance investigation suggested that there are bound water molecules and electrical conductivity studies confirm the existence of these four forms by the four different values of the activation energy. Variations of the activation energy on hydration have been interpreted qualitatively in terms of the energy band and energy levels of Fe²⁺ and Fe³⁺.