A stimulus - response method by using feed stream as tracer is used to study axial mixing and mass transfer characteristics in pulsed sieve plate extraction column of 15cm in diameter. The "true" height of transfer unit and the axial mixing coefficients evaluated by this method are in good agreement with those. evaluated by the conventional steady - state concentration profiles method. The present method is suitable for research work in large experimental columns. It is much simpler in operation

much less in time and material consumption. Furthermore a greater operation range

e. g. flow ratio (org. /aq. )

could be used in experiments with the present method.