Analysis of Decomposition Behavior of Low-concentrated Ferrocyanide Ion

The decomposition of low-concentrated ferrocyanide ion (≦51.28 × 10−4 mol dm−3) in acidic aqueous solution was investigated. While the concentration of ferrocyanide ion (CA) decreased with time, ferricyanide ion was formed: its concentration increased, and successively decreased through a maximal value. Therefore, we investigated first the decomposition behavior of sum of ferrocyanide and ferricyanide ions, i.e. hexacyanoferrate ions. The decomposition rate of hexacyanoferrate ions which followed first-order kinetics of CA increased with the rise in temperature and the drop in pH. That of ferrocyanide ion which also followed the first-order kinetics of CA increased with the rise in temperature but decreased with the drop in pH. The reaction mechanism of the decomposition of ferrocyanide ion and the formation of ferricyanide ion was discussed.