What Is Fractionation?

Alex Newth

Fractionation is a type of separation process used in many scientific disciplines; it is often seen in movies that feature scientists, surrounded by a large array of glass tubes and burners, attempting to distill or purify a mixture. This process takes a mixture and, through heat, a charge, acid or other separating factor, removes one or more elements from the mixture. Often used to confirm the purity of — or draw out an element from — a component in the mixture, fractionation is aimed at fractioning the mixture into separate and smaller parts, so the scientist can isolate a specific element he or she needs. While used most often in science, fractionation also is used in the culinary world.

Crude oil may be processed through fractionation.
Crude oil may be processed through fractionation.

In any separation process, the scientist working on the mixture needs to derive one or more components from a mixture. This mixture can be a solid, liquid, gas, isotope, or other type of mixture. The important aspect is that it is a compound mixture, with at least two elements, because a single element cannot be subjected to this fractioning process.

Some methods of fractionation use a centrifuge.
Some methods of fractionation use a centrifuge.

To begin fractionation, the mixture typically is placed in a flask or some type of holding apparatus. The next part of fractionation is highly dependent on what the mixture is. Some mixtures, such as plasma protein, will be mixed with a plasma fluid and then placed in a centrifuge. Others will have heat placed under a flask, so a quickly boiling substance in the mixture can travel up a fractionating column and down a condenser into another flask. If the scientist is attempting to separate the elements based on solubility, the mixture will be crystallized and the least soluble element will appear more prominently.

Fractionation is needed to purify mixtures. While single elements cannot be fractionated, rarely any elements in nature are found isolated without other elements. By fractioning the natural mixture, the scientist is able to purify the more valuable or necessary element from the mixture. For example, crude oil found in the Earth is not as useful or valuable as processed oil. The crude oil is subject to many chemicals to clear away the excess hydrocarbons, and the purified oil is fractioned off and used in the oil and fuel industry.

For culinary purposes, fractionation is employed as a method to make oils of different viscosities. The oils typically subjected to this process, which tends to use crystallization as the fractioning method, are palm, coconut and palm kernel oil. Oils with different viscosities allow the chef to use the oil for different cooking applications.

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