Synthesis of emeraldine base doped with the mixed valent bridging iron oxalate complex was done in the presence of varying quantities of H2O2. Characterization of the samples was carried out using elemental analyzer, FTIR spectrophotometer, scanning electron microscopy, four probe technique and Moessbauer spectroscopy. It has been observed that the reaction conditions are such that they bring about the partial reduction of iron from the +3 state to the +2 state, resulting in the formation of monovalent bridging iron oxalate complex dopant ion with iron existing in both +2 and +3 oxidation states. H2O2 at higher concentrations during the reaction is found to influence the polymer backbone, thus affecting the conductivity of the samples. Nanosized particles of oxides of iron in +2 and +3 oxidation states are formed in the polyaniline matrix on simple chemical treatment of the doped samples with an alkali.