THE KINETICS OF THE THERMAL DECOMPOSITION OF PYRITE

The kinetics of the thermal decomposition of purified pyrite to pyrrhotite and sulfur in a dynamic argon atmosphere have been studied over the temperature range 600 to 653 °C. The reaction was followed by the rate of weight loss as indicated by a quartz spring balance and also by the rate of progression of the pyrite/pyrrhotite interface into a cylindrical, compressed, polycrystalline pellet. The temperature coefficient of the reaction was found to be 69.5 ± 5.9, 64.7 ± 3.3, and 66.9 ± 5.1 kcal mole −1 , when the results were processed in three different ways. The pyrite/pyrrhotite interface was found to progress at a linear rate into the pellet at a given temperature; equations were derived to express the variation of reaction rate with temperature. Attempts to follow the early nucleation stage of the decomposition, using massive mineral crystals, proved unsuccessful.