Demonstration of Composition Changes in a Distillation Column by Use of Bromophenol Blue Indicator

In demonstrations of column distillation for the general public or in other demonstration settings, the audience often lacks the equipment or knowledge to access the distillation process. Distillation of solvents usually gives colorless solution. By adding bromophenol blue (BPB) to the distillation of water and ethanol, the authors have developed a setup sensitive to different ethanol concentrations, allowing direct visualization of the distillation process. The color in the distillation column changes from blue to yellow in the distillation column as ethanol concentration changes. Bromophenol blue indicator can also be used to quickly and semiquantitatively determine the ethanol concentration in binary ethanol-water mixtures in laboratory settings.