Question

Draw a diagram of bubble plate type fractionating column. When do we require such type of a column for separating two liquids. Explain the principle involved in the separation of components of a mixture of liquids by using fractionating column. What industrial applications does this process have?

Answer 1

Whenever the difference in the boiling points of two liquids is not much than simple distillation technique cannot be used to separate them. The vapours of such liquids are formed within the same temperature range and are condensed simultaneously and hence the technique of fractional distillation is used in such cases. In this technique, vapours of a liquid mixture are passed through a fractionating column before condensation. The fractionating column is fitted over the mouth of the round-bottomed flask. The vapours of the liquid with higher boiling point condense before the vapours of the liquid with lower boiling point. The vapours rising up in the fractionating column become richer in more volatile components and by the time the vapours reach to the top of the fractionating column, these become rich in more volatile components.