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  • Subject area(s): Science
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  • Published on: 15th October 2019
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Separation of Chemicals

The separation of chemicals is a technique that chemists have been using for many years to detect different chemical changes and to observe chemical reactions. Throughout the years, groundbreaking techniques have developed so that chemists can observe chemical separations in new ways. Three of these techniques are distillation, extraction, chromatography, filtration and recrystallization. As these processes were developed, it opened up a whole new world of chemistry that we didn’t even realize was there before.

Recrystallization is a common form of distillation, and is the most common way to purify or distill a solid. According to our textbook, during recrystallization, “enough solid is added to a solvent to create a saturated solution at an elevated temperature”. During this process the solvent becomes so saturated from the dissolved solvent, that leftover solid is a product of the recrystallization. One of the easiest chemical reactions that form a precipitate is the reaction AgNO3 + NaCl= AgCl. The NO3 is able to mix with the water or solvent used in the chemical reaction, while the AgCl is the precipitate, and cannot dissolve (Tro). Interestingly, recrystallization is used to make certain foods such as fudge and eggnog. More importantly, recrystallization is used to make the infrastructure of just about anything; steel. Steel, as a product, is crystalline, and goes through a process of recrystallization to create the strong, sturdy material that can withstand just about anything.

Distillation is the process of heating up a chemical compound until it begins to separate by either evaporation, or one of the substances separating itself. Distillation is mainly used to purify liquid substances and compounds, and helps concentrate the substances in the compound, or helps release them into the atmosphere by evaporation. According to Distillation: Equipment and Processes, “distillation operations are carried out in columns, that is, cylindrical pressure vessels with large height to diameter ratios, containing various kinds of internals chosen and arranged appropriately to enable cost-effective separation of binary or multicomponent, mainly liquid, feed mixtures into desired pure products or specified fractions.” Distillation columns are usually found in oil refineries. These refineries use the technology of the columns to help purify the oil, and get out any outliers and by products that they might not want in their products (Górak).

Another way that you can separate chemicals is by extraction. Extraction is seen in many everyday activities, whether you are fishing for your keys in your purse, or trying to get the lemon out of your water. The definition of extraction is basically taking a particle or substance and removing it from another. A common example is in coffee, where they use means of extraction to make caffeinated and decaffeinated products. However, in chemical separations using extractions, mainly solvents are used to extract compounds. Extraction usually involves a compound made of elements with polar and nonpolar tendencies. In order to separate these items, you put other polar and nonpolar solvents with the compound. Most of the time, the compounds will separate into the solvent with their same polarity, making it easy to evaporate the excess and have your successful extraction. Besides the decaffeination of coffee, hot water extraction is another process of extraction that we observe in everyday life. When you wake up in the morning and make a cup of tea, you are performing your own science experiment. As the hot water passes across and through the tea bag of your choice, it extracts the flavors from the ground-up stems and herbs that are inside of the tea bag. As a result, you get all of the flavor, and none of the gritty compounds that were used in creating the flavor.

Chromatography is a process that uses the attraction of certain compounds (usually in a liquid form) to another solid. During this process, the part of the liquid that is trying to be separated will disperse based on the chemical makeup of the compounds. For example, if one part of the liquid compound is more attracted to the solid used to separate than the other half, it will not move as fast when sliding over the solid. As a result, you can separate the fast-moving chemicals from the slow-moving ones, leaving you with a separated compound. Mikhail Tsvet invented chromatography in the early 1900’s when he was working on separating pigments of colors in the plants he was studying. Another part of chromatography involves a separation process called zone refining. In this process, extremely high temperatures are used to melt all substances that aren’t almost elemental in composition. For example, in order to crystallize the pure substance that you are searching for, you have to melt away all of the impure solvents, and you will be left with the remaining pure, solid substance. Chromatography is also used for some pretty cool things in everyday life. As an avid fan of CSI, I was intrigued when I found out that chromatography can be used to solve arson cases. By using chromatography, you can find what started a fire in a burned down house. Another cool thing that chromatography is used for is drug testing. Especially in high profile sports professions, chromatography is used to test for performance enhancing drugs in the bloodstream. (Heftmann)

Lastly, filtration is another way that you can separate chemicals. Although this process is only used in compounds that are easier to separate, filtration is equally as important as other separation methods. Filtration is the most common form of separation that you can find just about anywhere. For example, a vacuum cleaner is a filtration method. The electricity sucks up the particles from your carpet, and as they are sucked up, they are filtered through tiny, netted filtration systems in order to remove the dust, dirt and particles from the sample. At the same time, it provides an airway through which the excess air can travel which keeps your vacuum working and keeps it from stopping up. City sewage systems are other examples of filtration. As the sewage flows down the drain, they first come to a filter that filtrates all of the larger particles out of the system, and then as it flows down, the filtrates get smaller and smaller, slowly weeding out a lot of the particles in the water. In addition, the most common example of filtration is water filtration. From the filters that provide water in your fridge to the tap that comes out of the sink, water is being filtered 24/7 all around the world, and without it, no one would have any suitable drinking water.

Separation is one of the most important things in a chemist's career.

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