A KINETIC AND MECHANISTIC STUDY OF THE ISOTHERMAL DECOMPOSITION OF FERROUS OXALATE DIHYDRATE

A kinetic study has been made of the isothermal decomposition of ferrous oxalate between 5% and 638 K. The principal products of reaction are FeO (which disproportionates to Fe3O4 and Fe) and CO2 + CO (3:2 ratio). Yield-time data for the evolution of the gaseous products obeyed the Avrami-Erofe'ev (n = 2) equation, [-ln(1 - alpha)]1/2 = kt, characteristic of solid state nucleation and growth reactions. The activation energy calculated for this reaction was 175 +/- 7 kJ mol-1. Scanning electron microscopic examinations of partially decomposed salt showed that anion breakdown was not accompanied by reactant melting. The reaction mechanism is discussed. It is concluded that decomposition is initiated rapidly and proceeds as an interface advance process thereafter. The activation energy is comparable with values for decomposition of other oxalates and it is concluded that similar controls on the rate-limiting step apply.