Oscillatory oxidation of Mn(II) ions by hexacyanoferrates(III) and bistability in the reductions of MnO2 by hexacyanoferrates(II) in a CSTR

A new transition metal oscillator based on the oxidation of Mn2+ ions by Fe(CN)3−6 ions in a CSTR has been found. As well as the oscillations of the absorbance of the Mn(IV) species, pH-oscillations have been observed. In the reduction of manganese dioxide by Fe(CN)4−6 ions a kinetic bistability has been described. A skeleton mechanism described recently for Mn(II)H2O2 and Mn(II)Br2 oscillators has been applied here and further developed by the idea of the catalytic activity of colloidal particles and of the assistance of the pH-value change of both main processes, i.e. of the Mn(II) oxidation by Fe(CN)3−6 ions and of the Mn(IV) reduction by Fe(CN)4−6 ions. This appears to be the first case where both sides of a reversible reaction are autocatalytic.