Why is fractional distillation used

Fractional distillation

In this video, the implementation as well as the structure of a fractional distillation is presented.

In fractional distillation, a mixture of different liquid substances is separated by means of their boiling point. For this purpose, the mixture to be separated is usually placed in a flask on which a column is attached. Such a column, usually a Vigreux column in simple laboratory use, serves to improve the separation and its quality is measured by the number of theoretical plates. The distillation bridge with a cooler, often a Liebig cooler, is attached to the column. A so-called spider with several pistons to collect the various fractions is connected to this. In addition to the inlet and outlet for the cooling liquid, the distillation bridge also has an olive through which a reduced pressure can be applied; also a joint that is used to insert a thermometer into the system. The separation is done by heating the flask with the mixture to boiling. An oil bath is used for this, as the temperature of the oil bath can be set proportionally. After evaporation, due to their different boiling points, the substances rise one after the other in the column and then condense in the cooler, from where they drip into the selected flask of the spider. This has to be taken into account. that before the pure fraction of each substance there is a forerun, which is often a mixture of the various components. Only when the temperature read on the thermometer remains constant does the pure fraction pass. The progress of the distillation can be followed on the thermometer as the temperature rises and falls.