Two chemical test methods used for micromixing characterization, tile iodide-iodate test and the diazo coupling between naphthol and diazotized sulphanilic acid, have been compared. Experiments were carried out in a one litre stirred tank yielding segregation index as a function of stirring speed. It has been observed that the principal asset of the diazo coupling is to present a good sensitivity to micromixing effects and that the iodide-iodate test offers the advantages of being cheap and easy to handle. A simple phenomenological model, the incorporation model, has been used for the interpretation of experimental data. Micromixing times obtained are in good agreement with the turbulence theory and are independent of the chemical test chosen.