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What is the Difference Between Distillation and Fractional Distillation?

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  • Written By: Brad Cole
  • Edited By: Jay Garcia
  • Last Modified Date: 28 April 2017
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Distillation is a general term that describes a group of specific methods that use heat to separate mixtures. The two main types are simple and fractional. What can make this confusing is that some people incorrectly call simple distillation just "distillation." The two types use much of the same equipment and principles to separate mixtures, but the fractional method also uses a fractionating column. Fractional distillation is used when the boiling points of chemicals in a mixture are close to each-other, while the simple method is generally used when the boiling points are significantly different.

In simple distillation, a mixture containing chemicals with different boiling points is heated to a gentle boil. The chemical, now in gaseous form, travels upward and then over into a cooled tube called a condenser, where it becomes a liquid again. The condenser is angled slightly downward, and a purer version of the desired chemical empties into a receiving vessel at the bottom.

Fractional distillation is used when the boiling points of chemicals in a mixture are close to each-other, usually within 77°F (25°C). In this method, heat is added to the mixture until it begins to boil. The gas, usually purer than the mixture but still containing all of the chemicals, then travels up into a fractionating column. The fractionating column blocks the gas from directly rising by putting a large amount of surface area in its way, either by using a series of trays or plates, or by filling the entire column with packing material. The rising gas then condenses on the trays or other materials and becomes a liquid. The rising gases from below, however, heat this liquid again, causing it to distill again, and an even purer gas travels up to the next level of the column. Eventually, the gas makes it out of the fractionating column, is cooled to liquid, and empties into a receiving vessel.

In a laboratory setting, the two methods use much of the same equipment. The flasks, vessels, thermometers, condensers, clamps, adapters and even heating methods are interchangeable between the two. In fractional distillation, however, a fractionating column is set up between where the mixture is boiled (in a distilling flask) and the condenser, taking the place of the three-way adapter usually used.

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cloudel
Post 19

I love essential oils, and I once read that they are made through the process of steam distillation. The steam goes through the plant and the oil condenses.

Many plants that are used to make essential oils would not hold up to the extreme heat of their boiling points. The oil would not be of good quality. So, steam produces the best essential oils because you don't have to expose the plants to very high temperatures.

giddion
Post 18

@feasting – Regular distillation is used to make distilled water. I buy a few gallons of this a week at the supermarket. All the impurities have been boiled out of it in the distillation process.

Fractional distillation is used to refine crude oil. My brother-in-law is in this business, and he said that one batch of crude oil can yield many products, like diesel fuel, lubricating oil, and regular gasoline. Since they have different boiling points, fractional distillation is the best method.

I would guess that a lot of energy and time is saved by fractional distillation. Instead of having to do a separate refining for each product, they can make all of them at once.

feasting
Post 17

I see the difference here. What are some products that are made using distillation, and what are some that require fractional distillation? I understand the methods, but I'm not sure what is made using each one.

justjollyjay
Post 7

A very clear distinction, thanks!

anon155560
Post 6

Thank you. It was very useful and aided me in my research.

anon153404
Post 3

Super helpful. Thank you!

anon151935
Post 2

educatiional and helpful!

anon144743
Post 1

very helpful. thanks!

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