The study of the equilibrium in the system FeS-S2 (I) Dissociation equilibrium of pyrite at the low temperature

概要

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In the system FeS-FeS2 below 325°C, there have not been ascertained what kind of solid phase coexists at equilibrium with pyrite (FeS2), though some investigators have suggested it may be monoclinic pyrrhotite (Fe7S8). In order to establish the phase relation in this area, the authors measured the equilibrium of the system Fe1-xS-FeS2-S2 with the natural pyrite, in the temperature range 240-180°C, using the transportation method by the hydrogen gas stream. The experimental results show that the solid phase coexisting at equilibrium with pyrite is hexagonal pyrrhotite, whose d102-value is 2.070±0.001 A, corresponding to the composition 47.7 atomic % Fe and is not depending upon the temperature. The temperature dependance of the dissociation pressure is gained as follows: 2FeS2(Py)=2FeS(po)+S2 log Ps2=18662/T+19.27 (180°-240°C) From the additional heating experiment carried out in the air-atmosphere it is suggested that the monoclinic pyrrhotite may be produced under the existence of oxygen at the temperature below 325°C.
日本鉱物科学会の論文