Growth kinetics of gypsum during dissolution of colemanite with particle size less than 150 pm in aqueous sulfuric acid was studied in a batch reactor at 85 degrees C with a stirring rate of 400 rpm and initial CaO/SO42- ratio of 1.0. Kinetic data obtained from batch reactors was used to predict calcium ion concentration in continuous reactors by macrofluid and microfluid models. Model predictions were tested by experiments in four CFSSR in series each having mean residence time of 20 or 60 min. Calcium ion concentration predicted by macrofluid model in the first reactor was found to be closer to the experimental value indicating the significance of segregation. However, microfluid model provides the effluent calcium ion concentrations from the third and fourth reactors closer to experimental values. Verification of the model values by experimental data reveals that the methodology developed here is applicable to gypsum crystallization in n-CFSSR's in series. (c) 2007 Published by Elsevier B.V.