Pure α-Fe_2O_3 powder prepared by oxidation of Fe(CO)_5, was reduced to Fe_3O_4 by the hydrogen stream containing water vapour. The magnetic properties were measured at each state of reduction and the reduced grade was checked by the chemical and X-ray analysis. Fe_3O_4 thus prepared, was oxidized again and it was proved that the changes of the magnetic properties during oxidation and reduction, coincide with one another
