Main Difference – Distillation vs Extraction
All naturally-occurring compounds are not pure because there are several components mixed with each other. We call the unnecessary components present in our sample as impurities. There are several different techniques to separate or purify the substances in mixtures. Distillation and extraction are two such methods. Distillation is the action of purifying a liquid by a process of heating and cooling. Extraction is the action of extracting something, especially using effort or force. The main difference between distillation and extraction is that distillation includes the purification of a substance that is in a liquid mixture whereas extraction includes the purification of a substance that is either in liquid phase or solid phase.
Key Areas Covered
1. What is Distillation
– Definition, Technique, Different Types
2. What is Extraction
– Definition, Technique
3. What is the Difference Between Distillation and Extraction
– Comparison of Key Differences
Key Terms: Distillation, Extraction, Fractional Distillation, Separatory Funnel, Steam Distillation, Vacuum Distillation
What is Distillation
Distillation is the action of purifying a liquid by a process of heating and cooling. This technique uses the differences between boiling points of the components in the liquid mixture. Although gaseous mixtures can also be distilled by liquefying the gas from a gaseous mixture, this technique works better for liquid mixtures containing components having significantly different boiling points.
Different chemical substances have different boiling points. Therefore, when heating a liquid mixture, different chemical substances present in that mixture are converted into gases at different temperatures. By cooling the system gradually, we can collect the components that are condensed at different temperatures.
There are different types of distillation depending on the technique and the application.
Types of Distillation
- Simple distillation – used to separate two liquid substances having a significant difference in their boiling points.
- Fractional distillation– used for the separation of hydrocarbon fractions in the crude oil.
- Steam distillation – used to separate heat-sensitive substances.
- Vacuum distillation – used to separate components having very high boiling points.
Figure 1: The Apparatus for Distillation
The above image shows the apparatus for the distillation. Here, the liquid mixture is heated and the evaporated substance goes through the plastic tube. At the end of the tube, the condensing is done by passing cool water through the outer wall of the plastic tube. Then, the gases are condensed in the tube wall, transferring the heat to cool water. The water becomes warm. The condensed chemical substance is collected at the end of the tube.
By repeating the distillation process (doing a double distillation) a higher separation can be observed. As a summary, distillation includes heating → evaporating → cooling → condensing.
What is Extraction
Extraction is the action of extracting something, especially using effort or force. Extraction can be done for liquid-liquid separations and solid phase separations. The theory used in this extraction is the distribution of a substance in two different phases.
Let us consider a general apparatus of liquid-liquid extraction. This is done using a Separatory funnel. An aqueous solvent and an organic solvent are used as the two phases. The solvents can be chosen depending on the distribution coefficient of the chemical components that are going to be separated.
Figure 2: Apparatus for Extraction
First, the aqueous liquid mixture that is going to be separated is added. Then the Separatory funnel is filled with an aqueous phase and an organic phase. Since they are immiscible, the two layers are separated. The funnel is shaken several times carefully and allowed to stand for few minutes with the lid of the funnel opened. Then the two layers are collected in two different containers. The separation should be done several times in order to get accurate results. At the end, the required substance is in the organic phase. We can simply evaporate or use any other suitable technique to obtain pure substance from the organic phase.
Difference Between Distillation and Extraction
Definition
Distillation: Distillation is the action of purifying a liquid by a process of heating and cooling.
Extraction: Extraction is the action of extracting something, especially using effort or force.
Technique
Distillation: Distillation uses the differences between boiling points of chemical components in a mixture.
Extraction: Extraction uses the different solubilities of some components in two phases.
Degrees of Separation
Distillation: Distillation uses the relative volatility as a measure of the degree of separation.
Extraction: Extraction uses the selective solubility as a measure of the degree of separation.
Phases
Distillation: Distillation can be done only for liquid phase mixtures.
Extraction: Extraction can be done for liquid phase and solid phase mixtures.
Apparatus
Distillation: Distillation is done using distillation apparatus.
Extraction: Extraction is done using Separatory funnel.
Conclusion
Distillation and extraction are techniques used for the separation of components in mixtures of components. The main difference between distillation and extraction is that distillation includes the purification of a substance that is in a liquid mixture whereas extraction includes the purification of a substance that is either in liquid phase or solid phase.
References:
1. “Distillation.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 21 Feb. 2016, Available here.
2. Helmenstine, Anne Marie, Ph.D. “What Is Distillation?” ThoughtCo, Feb. 23, 2017, Available here.
Image Courtesy:
1. “161575” (Public Domain) via Pixabay
2. “Liquid liquid extraction” By Sjantoni – Own work (CC BY-SA 3.0) via Commons Wikimedia
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