Thermal decomposition mechanism of iron(III) nitrate and characterization of intermediate products by the technique of computerized modeling

The nonahydrate of iron(III) nitrate shows no phase transitions in the range of -40 to 0 A degrees C. Both hexahydrate Fe(NO3)(3)center dot 6H(2)O and nonahydrate Fe(NO3)(3)center dot 9H(2)O have practically the same thermal behavior. Thermal decomposition of iron nitrate is a complex process which has a different mechanism than those described for other trivalent elements. Thermolysis begins with the successive condensation of 4 mol of the initial monomer accompanied by the loss of 4 mol of nitric acid. At higher temperature, hydrolytic processes continue with the gradual elimination of nitric acid from resulting tetramer and dimeric iron oxyhydroxide Fe4O4(OH)(4) is formed. After complete dehydration, oxyhydroxide is destroyed leaving behind 2 mol of Fe2O3. The molecular mechanics method provides a helpful insight into the structural arrangement of intermediate compounds.