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The science of alcohol
The science of alcohol

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3 The process of distillation

As you have just discovered, the process of distillation is fundamental for the production of gin. Distillation is an example of a chemical process that is commonly utilised both in a laboratory setting and also on massive industrial scales – such as for gin production!

By definition, distillation is a process that exploits differences in the volatility of the components of a mixture. It is widely used both on a laboratory and an industrial scale to separate the components from a liquid mixture by selective boiling and condensation. Different components of a mixture have different boiling points, and it is these differences which enable the process of distillation to perform the separation.

So, distillation may be applied for the complete separation of pure components, or for partial separation to control the concentration of selected components within the mixture.

A typical apparatus set-up is illustrated in Figure 2.

This is an illustration showing a simple laboratory distillation set-up
Figure 2 A simple laboratory distillation set-up

Distillation is commonly used to separate ethanol – the alcohol in alcoholic drinks – from water. An example of such a distillation is illustrated in the following video on a laboratory scale.

Download this video clip.Video player: soa_alcohol_boc_vid002.mp4
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Considering what you have observed in the video, answer the following questions.

  • In a mixture of ethanol and water, which will evaporate first upon heating from room temperature?

  • Ethanol has a lower boiling point than water, so it evaporates first. The ethanol vapour is then cooled and condensed inside the condenser to form a pure liquid known as the distillate.

  • How do you know when it is ethanol that is boiling in the distillation process?

  • Assuming you know that the boiling point of water is 100°C, and you know that the solution contains only ethanol and water, when you start to see the distillate collecting in the receiving flask, you can read the temperature corresponding to the boiling point of this substance from the thermometer. If this temperature is lower than 100°C then the distillate must be something other than pure water, in this case it will be the ethanol.

  • Arrange the following stages into the order in which they occur during the distillation process: condensation, evaporation, heating, cooling

  • Heating – evaporation – cooling – condensation.

Distillation of alcohol can be done anywhere, whether it's in the home or a laboratory, but in most countries it is illegal to distil alcohol without a licence. You may have heard illegally-distilled alcoholic drinks referred to as ‘moonshine’. You will learn more about counterfeit alcohol in Week 8.