The variation of the specific rate of growth of ceria from cerium(III) hydroxycarbonate through a solid-gas reaction involving oxygen has been determined using an experimental method which consisted of modifying one of the chemical stresses (a partial pressure) during an experiment, whilst keeping the other partial pressures constant. The specific rate of growth and nucleation of ceria previously obtained from Mampel's model were confirmed. Another application was to ensure that, under the experimental conditions of the study, nucleation and growth of ceria from the solid-gas reaction were the only processes to be taken into account in the mass balance of the transformation.