Thermodynamics of Pyrrhotite at the Temperature Range of 800°∼1100°C

Abstract

In order to establish the relations between the sulphur activities and the compositions of pyrrhotite (FeS_1+x), the equilibrium measurements were carried out with the aid of the gaseous mixture of H₂-H₂S. The equations that relate the gas composition at room temperature to that at high temperature were derived thermodynamically by considering the species of S₂ and HS besides H₂ and H₂S. The experimental results permit to calculate the activities of sulphur, iron and FeS, ΔG_T⁰ of the formation of stoichiometric FeS, the heat and the entropy of mixing in pyrrhotite. The statistical thermodynamics of imperfect crystals was then applied tentatively to the system for interpreting the activity-composition relations in pyrrhotite.