Water and ethanol are made immiscible by the addition of potassium carbonate. After addition of potassium carbonate, the yellow solution separates into two phases, a colorless aqueous and blue organic phase. This demonstration can be used to introduce or illustrate the concept of intermolecular forces. Two test robes with stoppers, l0 mL each of ethanol and water, a few grams of potassium carbonate, a few drops of bromothymol blue indicator, and a drop of 1 M HCI are required. Ethanol, water, pH indicator and hydrochloric acid are combined in the first test robe to form a single-phase yellow solution.
Potassium carbonate is added to the second test tube.
The contents of the first test robe are added to the second test robe, and the mixture is stoppered and shaken. The solution will turn blue and separate into two phases, a colorless aqueous and blue organic phase. A number of test robes containing the reactants are distributed throughout a lecture hall, and the students are allowed to mix the reactants themselves. In this manner, the students get a better view of the salting-out process. An alternative approach is to scale up the reaction in two large graduated cylinders.