This problem has aiways studied by several authors, but it is not yet determined whether the reaction Fe₂O₃→Fe₃O₄→Fe or the reactionFe₂O₃→Fe₃O₄→FeO→Fe takes place.
In this paper, the changes in wegiht after reduction and oxidation of the ferric oxide and Anshan hematite are measured by the precision spring thermal balance with an electromagnet applied and the relations between the reactions involving the reduction and the oxidation, and the temperature are determined. In addition, the reducing and oxidizing reactions are discussed by the X ray analysis of the samples reduced and oxidized to different degrees.
From the experimental results, it may be inferred that the reduction takes place in the two stages Fe₂O₃→Fe₃O₄→Fe: and the ferrous oxide has no relation to the reduction. When the reduction of ferric oxide is carriel out at constant temperature, the first stage of reduction is carried out very rapidly; and then the second stage of reduction proceeds gradually in a straight line. In the case of reduction at the gas velocity of 70cc per minute, the reaction of Fe₂O₃→Fe₃O₄ begins at 250°C and completelyat 300°C. On the further reduction, the sample is partly reduced to metallic iron, which is not seperated, but exist as a solid solution with Fe₃O₄ up to the percentage reduction of 21%. The metallic iron is saturated at abeut 21% and seperated as a free metal. Then the reaction Fe₃O₄→Fe takes place very rapidly, until the sample is reduced completely to the metallic iron at 480°C
In the case of oxidation of the metallic iron reduced from ferric oxide, the reaction is the reverse of the reducing reaction: i.e., Fe→Fe₃O₄→Fe₂O₃. The reaction Fe→Fe₃O₄ proceeds very rapidly at 80-250°C. Then the oxidation Fe₃O₄→magnetic Fe₂O₃ commences to take place at about 300°C. and the magnetic hematite is altered to non-magnetic at about 500°C. Then the ferric oxide with rhombohedral structure is obtained at 850°C
When the reduction of ferric oxide and Anshan hematite are carried out at the constant gas velocity of 120cc per minute, the relations betweem the percentage reduction and the time of reduction at varions temperatures are obtained. At a constant temperature, varying gas velocity, the relation between the percentage reduction and the time of reduction is obtained.
In the reduction of the ferric oxide, the relation between the velocity of gas, the velocity of reduction and the reducing temperature is determined.

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