Sulphidation-rate measurements were carried out by using a microthermogravimetric apparatus which permitted mass changes in the sulphidized sample to be determined, as a function of time, with an accuracy of

the order of 10-7g. In one series of 2-stage kinetic experiments, the concentration of cation vacancies and their mobility were determined at 1073 to 1273K, for S activities of 10-1 to 104Pa. The self-diffusivity of Mn was calculated as a function of temperature and S activity:

D (cm2/s) = 6.98 x 10-4 exp[-123.5(kJ/mol)/RT] PS1/6

where PS was the S pressure.

Z.Grzesik, S.Mrowec: Journal of the Physics and Chemistry of Solids, 2001, 62[11], 1967-76