The separation principles of distillation and rectification

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All liquids have the ability to evaporate into vapor, but the volatility of different liquids varies. *Conventionally, the volatile component A in the liquid mixture is referred to as the light component, while the non-volatile component B is called the heavy component. Heating the liquid mixture above its bubble point to cause it to boil and partially vaporize necessarily requires yA > xA ； Conversely, to cool the mixed steam below its dew point and cause partial condensation, it must be true that xB > yB. The gas-liquid compositions obtained in the above two cases both satisfy the condition that both partial vaporization and partial condensation can enable a certain degree of separation of the mixture; separation is achieved through the difference in volatility of the various components within the mixture, and this is the basis for distillation and fractional distillation separation.