The regularities of phase formation during oxidation of aqueous solutions of FeSO 4 and (or) suspensions of Fe(OH) 2 at quasi-constant temperature and pH values have been studied for wide intervals of temperature (20 -85• C) and (4.0 -13.0) of the reaction medium. The produced nanodisperse materials have been examined by X-ray phase analysis, IR spectroscopy, scanning electron microscopy and X-ray fluorescence analysis, as well as by thermogravimetric analysis combined with thermal analysis and mass spectrometric analysis of released gases. The dependences of the phase, chemical and disperse compositions of the formed precipitates on the synthesis parameters have been revealed.