You might have been in a dilemma where you have to separate things like water and oil and some even wonder if its possible. Separation techniques are physical methods used for separating the constituents of various mixtures. The principle of separation is based on the physical properties of the constituents of the mixtures such as physical state, particle size,color, and melting point to mention a few.
Common Separation Techniques In Chemistry
In Chemistry, some of the common separation techniques include decantation, crystallization, evaporation, precipitation,and flotation. We would group them under the following categories:
- Separation of Solid from a Liquid
- Separation of a mixture of solids
- Separation of coloured mixtures
Techniques Used To Separate Solid From Liquid
There are separation techniques that are specially designed to separate a mixture comprising of a solid and liquid. A mixture is a combination of substances that can be mixed together,mechanically in any proportion. There are various types of mixtures which we would not go into because that is not our focus in this article. Some of the common techniques include:
Filtration method is used to separate a mixture of a solid in contact with a liquid in which it is insoluble that mans that the solid cannot or does not fully dissolve in the liquid. This particular method is based on the differences in the physical state and the insolubility of one component of the mixture in the other. Examples of mixtures that can be separated by filtration include: Suspended particles in a liquid or muddy water, sediments in a sample of water,and a saturated solution in contact with undissolved solid.
This method can also be seen in the domestic filters used in most homes to purify water. In the laboratory,a filter paper and a cone is used to separate mixtures.
Decantation also happens to be based on the insolubility of a solid in a liquid however,in decantation,the solid is of greater density hence it sinks and a great example is a mixture of sand and water.
Evaporation To Dryness
Evaporation is used to recover a solid from a liquid solvent in which it is soluble to give a solution. This method is only advisable when the sold has a very high melting point or cannot be easily decomposed by heating. It is based on the large difference between the melting point of the solid and the boiling point of the solvent.
This is the process of obtaining crystals of a solid from its saturated solution, without evaporating the solvent completely.
This is when crystallization process is repeated on a given solid sample using a fresh solvent.
This is the process whereby a mixture of two or more solid substances are crystallized,one after the other from the same solution. It is based on the huge difference in solubility of the solids in the same liquid solvent.
A centrifuge is a device that is used to separate fine solid particles in a colloidal solution. Centrifuging is based on the difference in the rates of sedimentation of different particles in a centrifugal field. it is used in hospital laboratories to separate the blood cells from plasma.
Precipitation method is based on the principle of solubility of a solid in two miscible liquids. In precipitation, two solids that are soluble in the same solvent are separated by the addition of another solvent in which one of the solids is insoluble.
Before understanding what Simple Distillation is, it is very vital to know the meaning of distillation. Distillation is the process whereby a liquid changes to vapour when heated and the vapour when cooled forms the liquid again. Simple distillation is primarily used to recover the solvent in a liquid solution and the principle is based on the difference in the boiling points of the constituents of the mixture.
Simple distillation can be used to obtain water from a mixture of ethanol and water.
Separation Of a Mixture Of Solids
The separation techniques that fall under this category include the following:
Sublimation is the process whereby a solid, when heated,changes directly to a gas, or a gas when cooled,changes directly to a solid without passing through the intermediate liquid state. To understand what sublimation is, get a camphor and it in an open container for days and after some days, you would find out that it has disappeared now, that process is calledsublimation.
Magnetization is one of the easiest separation techniques to understand because it can literally be done by anyone. Magnetization is used to separate a mixture of magnetic and non-magnetic solids and an example is a mixture of iron fillings and yellow sulphur powder.
Floatation method is based on the huge difference in the densities of the constituents of the mixture and it usually used to separate a mixture of two solids in which one constituent is light and the other is heavy. Another condition is that both solids must not be soluble in the liquid.
This technique is based on the difference in the particle sizes of the constituents of the mixture and an example is soil sample.
Separation Of A Mixture Of Liquids
A separating funnel is used to separate two liquids which do not mix(immiscible liquids) e.g water and kerosense. The use is based on the difference in the polarities of the liquids. Water is a polar solvent, while most organic solvents are non-polar hence immiscible with water.
Simple distillation cannnot be used to separate a mixture of miscible liquids with close boiling points because the separation would be incomplete an example is the mixture of petrol,kerosene,and diesel oil. On a large scale, crude oil is separated into its constituents in the refinery by fractional distillation.
Separation Of Coloured Mixtures
Chromatography means colour writing . It is a method of separating constituents of coloured mixtures of solids, liquid, and gases- such as in inks and dyes. Types f chromatography include gas, column,and paper/thin-layer chromatography.
Conclusion: These are some of the common separation techniques in Chemistry. Science is an ever evolving field meaning that more techniques can be added to these ones in the future.