What Is Distillation?

Distillation is a process of separating substances from a mixture. It involves heating a liquid to vaporize it and then cooling it to condense it into two separate fractions. It can be used to produce various products, including gasoline, kerosene, and alcohol.


It is a common misconception that vapor-liquid equilibrium exists in a liquid mixture. However, this is not the case.

It is a method of purification

Distillation is a process that converts liquid into vapor, which then condenses back into its original form. It can be used to increase the concentration of a particular component in a mixture or to purify the component from a mixture. It is often employed in the production of chemical products, such as kerosene and gasoline, as well as in the desalination of seawater. It is also used in the distillation of alcoholic beverages and fermentation processes.

In the simplest case, a liquid is heated to change its most volatile components into vapors that rise until they reach a cooler where they condense into a solid substance (e.g., water). The vapors can then be collected and separated into various fractions, with each one having a higher purity than the previous one. This is known as simple distillation.

The principle behind this method is that the boiling point of a liquid decreases with increasing pressure. This can be useful when trying to distill substances that cannot boil at normal atmospheric pressure without decomposition, such as flammable liquids or compounds that react with air molecules at high temperatures.

One common variation on this method is called distillation under reduced pressure or vacuum. This is usually done in a special glass apparatus with a receiver attached to a vacuum pump. This lowers the pressure on the receiver, which in turn lowers the boiling point of the liquid being distilled.

It is a process of separation

Distillation is a process of separation that involves the conversion of liquid into vapor, which then condenses to form a separate product. This is a fundamental chemical process, and it has many applications, including the separation of alcoholic beverages from fermented materials, distillation of crude oil into gasoline, kerosene, and lubricating oils, and desalination of seawater. In addition, it is used to purify chemicals produced through industrial synthesis.

The simplest distillation process starts with a mixture of liquids in a boiling flask. The mixture is heated by a hotplate and magnetic stirrer through a stainless steel jacket (orange, 2). The vapor rises through a Vigreux column and Liebig condenser, which is cooled by water that circulates through the ports 6 and 7. As the vapor cools and condenses, it drips into a receiving flask (blue, 8). The receiver can be connected to an evaporator or vacuum pump for continuous re-evaporation and condensation.

The evaporator allows the distillation to take place under a vacuum, which lowers the pressure of the surrounding environment and enables the mixture to boil at much lower temperatures than would be possible at atmospheric pressure. This process is useful for separating mixtures of volatile compounds, which cannot be boiled at normal temperatures or they will decompose. The mixture will eventually separate into a bottoms fraction and a tops fraction, which is the more volatile product.

It is a method of desalination

Distillation is a method of desalination that converts a mixture into its vapor phase and then condenses it back to liquid form. The process is exemplified at its simplest when steam from a kettle cools and returns to liquid form as drops of water. The process is used for many applications, including separating volatile organic compounds from other liquids and cleaning water. It is a highly energy-intensive process, but it can be improved through the use of advanced materials and design features that increase heat transfer efficiency.

The vapor pressure of the liquid rises with temperature. This means that a liquid boils when its vapor pressure equals atmospheric pressure. In normal distillation, the liquids are heated under ambient pressure. However, this is not always possible for highly toxic or corrosive chemicals. To overcome this problem, industrial plants operate at lower than ambient pressure, using low-temperature waste heat from electrical power generation or other sources.

Another important application of distillation is the removal of water from chemical synthesis processes. In the laboratory, this is often achieved by a process called flash evaporation, where the vapor is drawn through a device that reduces the pressure on the vapor stream.

This reduces the boiling point of the vapor and allows it to condense more easily in a separate container. The vapor is then collected in a fractionating column where it is separated into its components by a series of distillations. The vapor from each successive distillation is more pure than the previous one.

It is a method of chemical synthesis

Distillation is an important part of chemical synthesis because it allows us to separate components in a liquid mixture. The process of distillation involves heating a liquid to force the component with the lower boiling point into the gas phase. It is a common practice in chemical laboratories to use retorts for this purpose. This equipment has multiple chambers, with the vapors and condensates flowing through the plates to be collected at each stage. The process can be done continuously or in batch, depending on the needs of the application.

It is a common misconception that in a pure liquid, all components have the same boiling point and will evaporate separately, leaving each substance as a purely-formed vapor. This is not true, however, because there are always components in the mixture that cannot boil at the given pressure. These components are called azeotropes and will overlap to form a band in the boiling curves of each compound. It is possible to bias these curves so that the azeotrope no longer exists, but this will require increased energy, a new type of glassware, and extra power for the cooling system.

The process of distillation can be used for a variety of applications, from creating perfumes to separating crude oil into fuels. It is also used in alcoholic beverages to purify the product and remove volatile components. It is often combined with other techniques, such as crystallization and fractional distillation, to increase efficiency.