Distillation

What is distillation?

Distillation is a technique used to separate elements from a liquid mixture. This is achieved thanks to the differences in the volatility of the components.

Distillation allows for increasing the concentration of a mixture, separating the components of a mixture (in almost pure components), and purifying water.

In nature, at least one distillation process also occurs. In the water cycle, water is purified, leaving behind sediment and other elements with which it may have been mixed in its liquid state, through evaporation by the sun and its subsequent condensation and precipitation.

How does the distillation process work?

Depending on the substance to be distilled and for what purpose, certain distillation instruments will be used, as well as various parameters (temperature, time, etc.). However, the general distillation process can be summarized as follows:

1. A liquid is heated.
2. One of its components reaches the boiling point and evaporates before the other.
3. The first evaporated component condenses in a different container, while the second one remains in the first container.

Distillation is carried out in containers that have precise shapes to capture the vapor of the first element and lead it to condensation in a second container different from the one where the mixture was brought to a boil.

What are azeotropic mixtures?

These are made up of substances that have the same composition in liquid form and in vapor form in certain proportions. The components of these mixtures cannot be separated through the distillation process. However, there are a number of techniques that can, in some cases, achieve what’s called azeotropic distillation.

What is ideal distillation?

This is carried out in ideal conditions, starting from an ideal mixture with no technical or practical limitations that affect the process. This distillation exists only in theory, but it is useful to understand the process and lay out a guide for practical distillation.

An ideal mixture is one where the components retain the qualities they possess individually before being mixed. In reality, the components of a mixture undergo variations, but the ideal mixture is used to simplify the calculations and offer a reference for real mixtures.

What instruments are used in distillation?

Some of the instruments used for distillation are:

• Flask: a glass container containing the mixture to be distilled.
• Thermometer: to measure the temperature of the mixture in the flask and to know when the boiling point is reached.
• Condenser: an elongated glass tube connected to the flask through which the steam rises. When passing through the tube, the steam cools and condenses.
• Collection bottle: glass container where the condensed liquid is collected.
• Bunsen burner: a laboratory burner that acts as a heat source to heat the mixture in the flask.

Other containers used for distillation include:

• Distillation column: vertical tube used in fractional distillation. The mixture is poured in at the top of the column and heated. The components are separated and collected at different points in the column depending on their boiling point.
• Retort: a pear-shaped glass container used for distilling liquids at high temperatures. It has a lateral tube used to add the liquid to be distilled and an upper tube used to extract the steam produced during distillation.

What is distillation used for?

The desalination process can be used in different fields. Some of these are:

• In the laboratory
• In industry
• In medicine
• In cosmetics
• In food

What are the industrial applications of distillation?

Distillation is considered a unitary operation in industrial chemistry; that is, it’s a fundamental step for other processes, and it involves physical or chemical changes. Distillation is a physical (not chemical) process that still changes chemical compositions.

As a unitary operation, distillation has a large number of industrial applications. Some of them include:

• In hydrocarbons, for the stabilization of petroleum and its refinement for the production of by-products and chemical raw materials.
• In cryogenics, for the separation of air for industrial use from its various elements.
• Industrial chemistry.
• In food, for the production of alcoholic beverages and other fermented products.
• For water desalination.
• Water purification.