disturbance of the mass balance. Discard the "discarding" sample in a safe way. After the representative sample has been taken, keep the sample glasses in an upright position. Do not overturn them because of the possibility of evaporation of the sample. Record the refractive index for the taken overhead sample. In a similar manner take a sample of the bottom through valve v2. CAUTION! THIS SAMPLE WILL BE HOT, (take note of T9). Record the refractive index for this sample, too. Repeat this procedure every ten minutes until five samples of both overhead and bottom are obtained. Record the temperatures and Ti to calculate the average column temperature. Repeat this procedure for several different boil-up rates to cover over the operating range of the co The calibration graph developed in the previous Experiment B can be used to determine the concentrations of the components in the taken samples