The iron precipitates were prepared by adding sodium carbonate solution to ferrous chloride and ferric chloride solutions to pH=9 and pH=4.5, respectively. The thermal reaction of the iron precipitates was investigated by means of TGA, DTA and X-ray diffraction. In the former the crystallization of $alpha$-$Fe_2O_3$ begins at about 35$0^{circ}C$, while in the latter at about 30$0^{circ}C$, during the calclnation in air. In the iron precipitate from ferrous chloride solution, the activation energy for the crystallite-growth or $alpha$-TEX>$Fe_2O_3$</TEX> in air is about 7.6$ imes$104J/mole between 800 and 100$0^{circ}C$. As the result of X-ray diffration for the reduction product of hematite, it was found that maghemite, magnetite and wustite are formed and that hematite is transformed to magnetite through maghemite.