Different methods of Separation of Mixtures
Separation of Mixtures
1. Sublimation: A direct change of state from solid to gas is called sublimation. In this process gaseous substances on cooling give back the original substance. This phenomenon is only applicable when the vapour pressure of the solid phase is high. It can be used for substances which form sublimates in their separation from non-sublimate materials. Naphthalene, iodine and ammonium chloride are sublimable.
2. Distillation: On heating, a liquid is converted into vapour which converts into the liquid on cooling. This process is called distillation. In this process both vapourisation and condensation take place. It is used to purify liquids and to separate liquid mixtures.
Fractional Distillation: When the boiling points of various components are far apart, then simple distillation method is used to separate the mixtures. But if boiling points are closely related with each
other, then fractional distillation is used. In this process a fractionating column is used to separate
two or more volatile liquids. It is applied extensively in petroleum refining, separation of Oxygen,
N2, inert gases and Carbon dioxide from liquid air, manufacture of spirits such as – whisky, gin, rum
and brandy.
Steam Distillation: It is a method of distilling liquids that are immiscible with water by bubbling
steam through them. It is essential that the vapour pressure (and hence the boiling point) of the mixture of the two immiscible liquids should be lower than the vapour pressure of either, pure liquid. This method gives results, almost equivalent to those obtained from simple distillation.
3. Sedimentation and Decantation: This method is applicable when one component is liquid and another component is an insoluble solid (heavier than the liquid). If muddy water is kept undisturbed for some time in a beaker, the particles of earth (clay and sand) settle at the bottom leaving a clear liquid at the top. This process is called sedimentation. The clear liquid (water in this case) can be gently transferred into another beaker. This process is known as decantation.
4. Filtration: Separating the solid particles through a filter is called filtration. The filter is made up of a porous material (such as paper or fine glass wool) which prevents solid particles from passing through.
There are some applications of this method which are useful in our daily life such as -
purification of the domestic water supply by filtering river water through a layer of sand.
removal of solid particles in engine oil in car engines by air filters.
filtration of tea from tea leaves in the preparation of tea, etc.
Gas filtration involves removal of solids (called dust) from a gas-solid mixture. Liquid filtration is
used for a liquid-solid separation in the manufacture of chemicals, polymer products, medicines, beverages and foods, in mineral processing, in water purification, in sewage disposal, in the operation of machines such as internal combustion engines.
5. Crystallization: This process involves the formation of crystals from a liquid or gas. Separation and
purification of solid substances is done by this method. During this process, firstly mixture is heated
with a suitable solvent to its boiling point and then the hot solution is filtered. The filtrate is slowly
cooled down to room temperature. Thus pure solid crystallizes out. This is separated from the filtrate
by filtration and dried. In fractional crystallization the components of the mixture crystallize out at
different intervals of time.
6. Chromatography: This is a technique for analysing or separating mixtures of gases, liquids or dissolved substances. The components of a mixture move differently on an adsorbent material (filter paper), blotting paper, solid surface of Silica, etc. when the liquid moves through them. They travel to different extents through the adsorbent material and thus get separated. Separation of coloured materials from green vegetables, ink are common examples.
1. Sublimation: A direct change of state from solid to gas is called sublimation. In this process gaseous substances on cooling give back the original substance. This phenomenon is only applicable when the vapour pressure of the solid phase is high. It can be used for substances which form sublimates in their separation from non-sublimate materials. Naphthalene, iodine and ammonium chloride are sublimable.
2. Distillation: On heating, a liquid is converted into vapour which converts into the liquid on cooling. This process is called distillation. In this process both vapourisation and condensation take place. It is used to purify liquids and to separate liquid mixtures.
Fractional Distillation: When the boiling points of various components are far apart, then simple distillation method is used to separate the mixtures. But if boiling points are closely related with each
other, then fractional distillation is used. In this process a fractionating column is used to separate
two or more volatile liquids. It is applied extensively in petroleum refining, separation of Oxygen,
N2, inert gases and Carbon dioxide from liquid air, manufacture of spirits such as – whisky, gin, rum
and brandy.
Steam Distillation: It is a method of distilling liquids that are immiscible with water by bubbling
steam through them. It is essential that the vapour pressure (and hence the boiling point) of the mixture of the two immiscible liquids should be lower than the vapour pressure of either, pure liquid. This method gives results, almost equivalent to those obtained from simple distillation.
3. Sedimentation and Decantation: This method is applicable when one component is liquid and another component is an insoluble solid (heavier than the liquid). If muddy water is kept undisturbed for some time in a beaker, the particles of earth (clay and sand) settle at the bottom leaving a clear liquid at the top. This process is called sedimentation. The clear liquid (water in this case) can be gently transferred into another beaker. This process is known as decantation.
4. Filtration: Separating the solid particles through a filter is called filtration. The filter is made up of a porous material (such as paper or fine glass wool) which prevents solid particles from passing through.
There are some applications of this method which are useful in our daily life such as -
purification of the domestic water supply by filtering river water through a layer of sand.
removal of solid particles in engine oil in car engines by air filters.
filtration of tea from tea leaves in the preparation of tea, etc.
Gas filtration involves removal of solids (called dust) from a gas-solid mixture. Liquid filtration is
used for a liquid-solid separation in the manufacture of chemicals, polymer products, medicines, beverages and foods, in mineral processing, in water purification, in sewage disposal, in the operation of machines such as internal combustion engines.
5. Crystallization: This process involves the formation of crystals from a liquid or gas. Separation and
purification of solid substances is done by this method. During this process, firstly mixture is heated
with a suitable solvent to its boiling point and then the hot solution is filtered. The filtrate is slowly
cooled down to room temperature. Thus pure solid crystallizes out. This is separated from the filtrate
by filtration and dried. In fractional crystallization the components of the mixture crystallize out at
different intervals of time.
6. Chromatography: This is a technique for analysing or separating mixtures of gases, liquids or dissolved substances. The components of a mixture move differently on an adsorbent material (filter paper), blotting paper, solid surface of Silica, etc. when the liquid moves through them. They travel to different extents through the adsorbent material and thus get separated. Separation of coloured materials from green vegetables, ink are common examples.
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