<報文>硫化第一鐵の酸化に於ける自觸過程について

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In the reaction expressed by solid_1+gas_1=solid_2+gas_2,e.g., the roasting reaction of sulphide ores, the diffusion rate of gas has commonly been regarded as the rate-determining step. But this does not seem to be always true, especially in the initial stages of the reaction. According to Langmuir, there should be no reaction between gas_1 and solid_1,if there were no trace of solid_2 present. He assumes, however, that in this case, gas_1 would be slowly adsorbed by solid_1,and gradually nuclei would develop. This initial slowness to react may be called the "induction period". The phase boundaries thus formed would cause an autocatalytic acceleration in reaction, and a maximum value in reaction rate is passed through in the course of the reaction (Fig.1). In view of deficiency in compilation of studies concerning the autocatalytic reaction, the literatures in this field were collected and summarized by the authors, and the present oxidation reaction of ferrous sulphide was thereby explained. Kinetics of oxidation of artificial ferrous sulphide was studied by means of a flow method. 100 mg of granular sample was oxidized with abundant supply of air, and the initial stage of the present reaction was found to be clearly autocatalytic. The reaction rate increased remarkably with increasing fineness of sulphide particles (Fig.2); when the average diameter of sulphide particles in a constant weight was increased by twofold, the initial reaction rate increased fourfold. This result seems to be explained by the theory of adleneation. The reaction rate also increased with increasing temperature, and it was evident that the decrease in temperature intensified the autocatalytic nature of the sulphide, while the increase in temperature enfeebled it (Fig.3). Perhaps this is because the rates of formation and propagation of nuclei change with temperature. When some reaction nuclei had been formed previously on the sulphide particles by a separate short-period oxidation, the reaction rate of subsequent oxidation showed a remarkable increase. But this acceleration in rate diminished with the increase in temperature of subsequent oxidation (Fig.3). It also depended upon the conditions of pretreatment ; the lower the temperature of pretreatment was, the more remarkable the acceleration was (Fig. 4). Even an extremely faint pre-oxidation caused an appreciable acceleration in subsequent oxidation and the reaction rate increased up to a certain constant value with increasing sulphur amount reacted in pretreatment (Fig.5).
東北大学の論文
1951-10-03

<報文>硫化第一鐵の酸化に於ける自觸過程について

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