The leaching kinetics of tincal in oxalic acid solutions was investigated in this study. The effects of parameters reaction temperature, acid concentration, solid to liquid ratio, particle size and stirring speed on tincal leaching were determined in the experiments. It is observed that the leaching rate increases with increasing reaction temperature, stirring speed and decreasing solid to liquid ratio and particle size. The experimental data tested the reaction control models and the best model for the leaching rates of tincal was the product layer model. The activation energy of the process was calculated as 35.14 kJ mol(-1). (c) 2006 Elsevier B.V. All rights reserved.