Roasting reaction of ferrous sulfide

Abstract

The rate and mechanism of oxidation of ferrous sulfide have been studied by means of the spring balance and X-ray diffraction analysis over the temperature range from 500° to 700°C. The complete oxidation to oxides begins at 600°C. At the initial stage of oxidation, a slight increase of weight was found. It was observed by X-ray that the deficiency of iron ion in FeS occurs in this stage. This is interpreted as follows: iron ion reacts with oxygen by migrating from the interior of FeS crystal to the surface, without evolution of SO₂, until the deficiency of iron attains to a limiting value. Above 600°C the rate of oxidation does not change with temperature, so the rate-determining factor is diffusion of gas. Since the observed rate of oxidation depends upon the amount of the sample, the diffusion in the bed of the sample may determine the rate.