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Separation of Mixtures

Updated on November 03, 2011

There are a wide range of separation Techniques that range from the simplest such as magnetization to a complex like Electrophoresis. Here we will be discussing seven unique ways of separating mixtures in a simplified manner.


Filtration is used to separate liquids from solid particles. It is suitable for the separation of undissolved solutes from a solution. A typical example of filtration is during elementary chemical laboratory experimentation where filter paper is used to separate precipitates in qualitative analysis. Another example of filtration is in everyday home cooking where Kitchen filter is used to separate water from rice after boiling. Mixture of sand and water and the extraction of corn starch (Pap) also employs filtration where the tiny pores of the filter only allows the tiny small particles to pass through with the flushing liquid while the larger irregular shape particles are trapped at the top of the Filter.


Sieving is used to separate solid particles of different shapes and sizes. The Nigerian Garri Filter is a typical sieve used to separate the Garri from the large particles. Fine sand particles can also be recovered from a mixture of Sand and Rock using a Sieve. Here, the Rock is trapped at the top of the sieve while the Sand is collected bellow.


Distillation can be used to separate Solids from Liquids or Liquids of wide range of difference in boiling points. The mixture to be separated is heated in a tightly closed container that is connected from the top via a Tube through a cooling chamber to a collection point. A typical example of Distillation is the distillation of Ethanol after Fermentation. Here, the mixture is heated within the range of the boiling point of Ethanol (78°C) to allow for the separation of the Ethanol from Water whose Boiling point is 100°C.

There is another form of Distillation called the Fractional Distillation. This method is used when the aim is to separate components of very close Boiling Points. A typical example is the fractional distillation of Crude oil to obtain Kerosene, Gasoline, Grease, e.t.c.



Decantation is used to separate suspensions once they are settled. I is also applicable to a wide range of mixtures that are separated by special layers. It is a potent separation technique for separating the components of a Suspension. The mixture is allowed to settle down and the liquid upper layer is poured into another container living the sediments behind. After the extraction of fresh Pap from grounded maize, the extract is left undisturbed for several hours before decantation.


Centrifuging involves the use of a machine called a centrifuge to spin a sample of mixtures of different densities. Medical laboratories are known to use centrifuge to separate red blood cells from Plasma. Spinning of a sample of blood in a test tube allows the denser red blood cells to move outward and the less dense plasma inwards to the rotation axis, thus separating the mixture.


Salt Solution can also be separated by Distillation to recover the Solute (Salt ) and the Solvent (Water). The applied heat allows the water to change from liquid state to its gaseous state (Steam) thus escaping from the top through a tube to the collection point., while the solid salt crystal is left behind in the heating container.


Chromatography separates mixtures on two phases: the mobile phase and the stationary phase. The mixture to be separated is dissolved in the mobile phase while the actual separation process is effected on the stationary phase. The various constituents of a mixture are made to travel through the stationary phase in a way that allow for separation due to differences in particle size and polar affinity. Examples of Chromatography are thin layer chromatography, column chromatography and paper chromatography. Paper chromatography is commonly used to separate plant pigments such as Chlorophyll.


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