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Thin Layer Chromatography

Melting Point

Simple Distillation

Column Chromatography

Infrared Spectroscopy


Solubility Testing



Gas Chromatography-Mass Spectrometry

Classification Tests-Halides

Fractional Distillation


Fractional Distillation
(Adapted from Mohrig, pp. 118-121)

Fractional distillation is a technique used when separating a mixture of two liquids that do not "behave" well enough to use simple distillation. In this case simple distillation would not be enough to fully separate the two liquids. The distillate would contain a majority of one liquid but would still contain a little of the second. To further separate this resulting distillate, one would need to redistill this mixture. Depending on the two liquids in question, many simple distillations would be required to obtain pure liquid.

Fractional distillation essentially performs these "redistillations" automatically in a portion of the fractional distillation apparatus called the fractionating column. As the mixture boils, it turns to vapor and rises up the column. It reaches a certain point up the column and condenses. It then turns to vapor again and rises a little bit further up the column. This continues until the vapor rises all the way up the column and condenses in the condenser. At this point, the liquid has been completely purified.

The procedure for fractional distillation is very similar to that of simple distillation. Once you have set up your fractional distillation apparatus, place the liquid to be distilled in the distilling flask. The flask should be no more than two-thirds full at the start of the distillation because the contents may foam and boil over. Remember to place one or two boiling stones in the flask to promote even boiling. Ensure that all joints are tight. Turn on the water for the condenser. Only a small stream of water is needed; too much water pressure will cause the tubing to pop off. Turn on the Variac and the distillation can begin. As always, never boil the flask to dryness because, in some cases, high-boiling explosive peroxides can become concentrated. Stop the distillation when a small amount of liquid is left in the distilling flask. Turn off the Variac and remove the heating mantle to allow the flask to cool more quickly.