黄鉄鉱の酸化反応生成物に関する研究

酸化反応生成物の磁気的性質

抄録

The properties of the oxidation products of pyrite, above all, the composition of FeS_1+x formed at the intermediate stage of the oxidation and the conditions of formation of Fe₃O₄, were investigated by the methods of measurement of the relative intensity of magnetization, thermomagnetic analysis, and X-ray. Results obtained were summarized as follows;
(1) The intensity of magnetization of the products increases along the oxidation, reaching at its; maximum value in its way, and after then, it dereases. In the atmosphere whose partial pressure of oxygen is 0.01 atm., this maximum value is remarkably higher than that of the oxidation products, which were formed in the atmosphere whose partial pressure of oxygen is above 0.01 atm.
(2) This maximum of the intensity of magnetization was found, by thermomagnetic analysis and X-ray measurement, to be caused mainly by the formation of Fe₃O₄. In the oxidation in the atmosphere whose partial pressure of oxygen is 0.01 atm., it was found that Fe₃O₄ was stable just to the end of the oxidation and Fe₂O₃ was formed abruptly at the end of the oxidation. On the contrary, in the atmosphere of more than 0.03 atm. of oxygen, Fe₂O3 and small amount of Fe₃O₄ was found, to be formed at the comparatively initial stage of the reaction.
(3) FeS_1+x formed at the intermediate stage of the oxidation was certified as a ferromagnetic one, and its composition is near the upper limit of solubility of sulphur in FeS_1+x.
(4) From above-mentioned results of studies, the mechanism of the oxidation in a layer of fineparticles of pyrite was considered. According to Niwa and Tohata, the oxidation in the layer of fine: particles of pyrite proceeds from the surface towards the interior. Therefore, the partial pressure of oxygen decreases along this way and the layers of the oxidation products after the thermal decmposition are arranged from the surface as follows; Fe₂O₃, Fe₃O₄, FeS_1+x. From the results of (1) and (2), it may be said that in the oxidation at low partial pressure of oxygen in the atmosphere, among, these layers of oxidation products, the Fe₃0₄ layer becomes much thicker in the intermediate stage of the reaction.