Simple distillation

The easiest case: one component leaves as vapour and the rest simply cannot.

Simple distillation

Simple distillation is used to separate the components of a mixture in which a volatile component and components that are not volatile are present together. In distillation only the volatile component vaporises; the others stay behind in the solution.

The worked case — well water

Suppose a sample of well water is subjected to distillation. Besides the water it holds various salts dissolved in it and a small amount of gases. As it warms gently the gases leave and are not condensed. The boiling points of the salts are very much higher than the boiling point of water. So when the well water sample is heated and vaporised, only the water vaporises. The salts can be seen to have been deposited at the bottom of the vessel in which the water was heated.

Figure to be added

A simple distillation train: a round-bottomed flask of well water on a stand over a flame, a thermometer in its neck, a Liebig condenser sloping down from it with water entering low and leaving high, and a beaker of distilled water at the outlet.

Why it needs no special control

Because of the size of that gap in boiling point, this distillation needs no special control of conditions. Nothing else is close enough to water to come over with it. That is exactly why it is counted as simple, and why apparatus as ordinary as a Liebig condenser is enough for it.

Simple distillation works when one boiling point is far below all the others. When they are close together it does not, and the next page is about what to do then.

Where it is used

The figure shows an assembly prepared for obtaining distilled water from a sample of well water. Some countries in the world use this method to obtain drinking water from sea water.