The Purification of Organic Compounds by Distillation

Vapor-pressure curves of water, ethyl alcohol, and ether 

As the liquid boils in the flask it displaces the air and finally the vapor passes through the side tube into the inner tube of the condenser, which is kept cold by circulation of tap water through the outer jacket. The gaseous molecules of the vapor, on cooling, coal- 

Pressure Boiling Point Pressure Boiling Point 

The apparatus commonly used in distillations under reduced pressure is discussed in detail in Experiment 45 (page 232), in which the method is employed. For the present discussion it will be sufficient to note that a suction pump is used to reduce the pressure within the distilling flask. 

Fractional distillation. Mixtures of liquids which are miscible in each other, such as water and alcohol, or water and acetone, may be regarded as solutions. Since each compound exerts its own vapor pressure and lowers the vapor pressure of the other, the mixture will boil when the combined vapor pressure equals the atmospheric pressure, and the boiling point of the solutions will change during the distillation. The distillate will contain a mixture of the two compounds. It is possible by collecting the distillate in separate portions and repeating the distillation to separate part of each component in the pure state. This process is called fractional distillation and is discussed in detail in the next experiment. 

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