Distillation is a widely used physical separation technique that harnesses the difference in

boiling points (or volatilities) of components in a liquid mixture to separate them. It's not a
chemical reaction, but rather a process involving changes of state.
Here's a breakdown of the process:
The Core Principle
The fundamental idea behind distillation is simple:
1.​ Vaporization: When a liquid mixture is heated, the component with the lower boiling point
(the more volatile component) will turn into a vapor more readily than the others.
2.​ Condensation: This vapor is then cooled, causing it to condense back into a liquid.
3.​ Collection: The newly condensed liquid, which is now enriched in the more volatile
component, is collected separately.
How it Works (General Steps):
1.​ Heating: The liquid mixture is placed in a distillation flask or still and heated.
2.​ Vaporization: As the temperature rises, the component with the lowest boiling point starts
to vaporize, creating a gas (vapor).
3.​ Ascension: The vapor rises and moves away from the remaining liquid mixture.
4.​ Condensation: The vapor then enters a condenser, which is typically a tube surrounded
by a cooling jacket (through which cold water circulates). The cool surface of the
condenser causes the hot vapor to lose heat and condense back into a liquid.
5.​ Collection: The condensed liquid, called the "distillate," flows into a separate receiving
flask. The less volatile components with higher boiling points remain in the original
distillation flask.
Types of Distillation:
Different types of distillation are employed depending on the nature of the mixture and the
desired purity:
●​ Simple Distillation: Used when the boiling points of the liquids in a mixture are
significantly different (typically a difference of at least 25^\circ C or more), or to separate a
liquid from non-volatile solids.
●​ Fractional Distillation: Used when the boiling points of the components are closer
together. It utilizes a "fractionating column" placed between the distillation flask and the
condenser. This column provides a large surface area for repeated cycles of vaporization
and condensation, leading to a much better separation and higher purity of the
components. This is crucial in industries like petroleum refining.
●​ Steam Distillation: Used for separating heat-sensitive organic compounds from
non-volatile materials. Steam is passed through the mixture, lowering the boiling points of
the components (as the total vapor pressure is the sum of the partial pressures of water
and the organic compound), allowing them to distill at lower temperatures than their
normal boiling points, thus preventing decomposition.
●​ Vacuum Distillation: Performed under reduced pressure (a vacuum). Lowering the
pressure reduces the boiling points of the liquids, allowing them to vaporize at much lower
temperatures. This is particularly useful for compounds that are unstable at high
temperatures or have very high boiling points.
●​ Azeotropic Distillation: Used to separate azeotropes (mixtures that boil at a constant
temperature and have the same composition in the liquid and vapor phases, making them
difficult to separate by simple or fractional distillation). This often involves adding a third
component (an "entrainer") to break the azeotrope.
●​ Extractive Distillation: Similar to azeotropic distillation, but a non-volatile solvent is
added to alter the relative volatilities of the components, making them easier to separate.
Applications of Distillation:
Distillation is a vital process with widespread applications across various industries:
●​ Petroleum Refining: Separating crude oil into various valuable fractions like gasoline,
diesel, kerosene, lubricating oils, and asphalt based on their boiling points.
●​ Alcohol Production: Concentrating ethanol from fermented beverages to produce spirits
like whiskey, vodka, and rum.
●​ Water Purification: Producing distilled water by separating water from impurities and
dissolved minerals. Used in laboratories, for medical purposes, and sometimes for
drinking.
●​ Chemical Manufacturing: Purifying and separating a vast array of chemicals, solvents,
and intermediates in the pharmaceutical, petrochemical, and other chemical industries.
●​ Essential Oil Extraction: Extracting fragrant essential oils from plants for use in
perfumes, cosmetics, and food flavorings.
●​ Natural Gas Processing: Separating different components of natural gas, such as
propane, butane, and ethane.
●​ Solvent Recovery: Recovering and reusing solvents from industrial processes, reducing
waste and cost.
In essence, distillation is a powerful and versatile tool for separating and purifying liquids,
playing a critical role in numerous aspects of our daily lives and industrial processes.