The chlorination Of Sm2O3 in the presence of carbon using the gaseous mixture Cl-2(g) + Ar(g) has been studied by thermogravimetry. The effects of both the temperature between 200 and 950 degreesC and the total gas flow rate between 2.1 and 7.91h(-1) on the reaction rate were analyzed. The starting temperature of reaction, the stoichiometry and kinetic regimes of the reaction were obtained. Reactants and products were analyzed by X-ray diffraction (XRD) and electronic dispersive spectroscopy (EDS). The temporal evolution of the solid microstructure was followed by scanning electron microscopy (SEM). (C) 2003 Elsevier Science B.V. All rights reserved.