Main Difference – Reflux vs Distillation
Reflux and distillation are two chemical techniques. Reflux is a technique that involves the condensation of vapors which are then returned back to the sample. It is used in laboratory distillation processes. Distillation is the action of purifying a liquid by a process of heating and cooling. Distillation can be found in four major types as simple distillation, fractional distillation, steam distillation and vacuum distillation. The main difference between reflux and distillation is that reflux method is used to complete a certain chemical reaction whereas distillation is used to separate components in a mixture.
Key Areas Covered
1. What is Reflux
– Definition, Technique
2. What is Distillation
– Definition, Different Types of Distillation
3. What is the Difference Between Reflux and Distillation
– Comparison of Key Differences
Key Terms: Distillation, Fractional Distillation, Petroleum Refinery, Reflux, Simple Distillation, Steam Distillation, Vacuum Distillation
What is Reflux
Reflux is a technique that is used in chemical laboratories to dissolve components that are hard to be dissolved. It involves continuous recycling of the solvent. It is very useful in completing a chemical reaction that is difficult to be done.
Refluxing is used in large-scale industries such as petroleum refineries. In laboratory scale, it is used in a simple apparatus which is composed of a round-bottomed flask, a condenser, a water bath and heat source. A mixture of reactants and the solvent is added to the round-bottomed flask. It is connected to a long condenser which is open in its top end.
Figure 1: Apparatus for Refluxing
When the round-bottomed flask with components is heated in the water bath, the reaction mixture starts to boil. Vapors are produced from the mixture. This vapor is condensed by the condenser. Then the droplets return to the reaction mixture due to the force of gravity. This method will thermally accelerate the chemical reaction. The reaction is done at a chemically controlled temperature and ambient pressure.
What is Distillation
Distillation is the action of purifying a liquid by the 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 application. They are,
- 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.
Simple Distillation
In simple distillation, the evaporated substance goes through the plastic tube when the liquid mixture is heated. Condensing is done at the end of the tube 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 and the condensed chemical substance is collected at the end of the tube.
Fractional Distillation
Fractional distillation is the process used to separate hydrocarbon components in crude oil. This method includes the separation of important components according to the difference between their boiling points. In other words, it uses distillation for the fractionation of crude oil.
Steam Distillation
Steam distillation is a process used to separate heat-sensitive components in a mixture. Thus, it is used as a purification technique for compounds having impurities. The components in the mixture should be volatile in order to do this separation. The principle behind steam distillation process is to separate the components by vaporizing them at temperatures below their actual boiling point. Unless otherwise, some compounds may decompose at their boiling points and the separation cannot be done accurately.
Figure 2: Steam Distillation Apparatus
Vacuum Distillation
In Vacuum distillation, the pressure above the liquid mixture is reduced to a value less than its vapor pressure; this causes the evaporation of most of the volatile components.This method may or may not require heating.
Difference Between Reflux and Distillation
Definition
Reflux: Reflux is a technique used in chemical laboratories to dissolve components that are hard to be dissolved.
Distillation: Distillation is the action of purifying a liquid by the process of heating and cooling.
Purpose
Reflux: The purpose of refluxing is to dissolve components in a reaction mixture that are hard to be dissolved and to complete to chemical reaction.
Distillation: The purpose of distillation is to separate different components in a mixture.
Apparatus
Reflux: The reflux apparatus is composed of a round-bottomed flask, a condenser, a water bath and heat source.
Distillation: The distillation apparatus is composed of a round-bottomed flask connected to a Y adapter which is connected to a condenser. The condenser is connected to a receiving flask.
Conclusion
Refluxing and distillation are chemical techniques used in many laboratories. The main difference between reflux and distillation is that reflux method is used to complete a certain chemical reaction whereas distillation is used to separate components in a mixture.
Reference:
1. “Reflux.” Wikipedia, Wikimedia Foundation, 13 Nov. 2017, Available here.
2. Helmenstine, Anne Marie. “What Is Distillation?” ThoughtCo, Feb. 23, 2017, Available here.
Image Courtesy:
1. “Reflux English” (CC BY-SA 3.0) via Commons Wikimedia
2. “Steam dist” By Joanna Kośmider – Own work (Public Domain) via Commons Wikimedia
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