Heterogeneous mixtures use sieving, filtration, handpicking, etc. as separation techniques.
On the other hand, for the homogeneous mixture and sometimes a heterogeneous mixture, special separation techniques need to be used like evaporation, centrifugation, chromatography, sublimation, separating funnel, etc.
The various physical processes which are commonly used to separate the constituents of mixture are:
Separation by Solvent:
A mixture of sugar and sand can be separated by using water as solvent.
A mixture of sulphur and sand can be separated by using carbon disulphide as solvent.
Separation by a Magnet:
If a mixture contains iron as one of the constituents, it can be separated by using a magnet.
Separation by Filtration:
Filtration is used for separating insoluble substances form a liquid. A mixture of chalk and water is separated by filtration.
Separation by Evaporation:
Evaporation is the mechanism to separate the volatile component that is solvent or solid substance from its non-volatile solute which is water or any other form of liquid.
The use of process of evaporation for separating a mixture is based on the fact that liquids vaporise easily whereas solids do not vaporise easily.
Obtaining coloured component (dye) from blue/ black ink
Obtain salt from sea water
Separation of Mixture of Two or More Liquids:
A mixture of miscible liquids is separated by the process of fractional distillation.
A mixture of immiscible liquids is separated by using an apparatus called separating funnel.
Separation by Centrifugation:
Centrifugation is the process of separating suspended particles from a liquid like colloids by churning the liquid at a high speed.
Principle: The principle is that denser particles are forced to the bottom and lighter stay at the top when spun rapidly.
This process is based on the shape and size of particles, viscosity of the medium and speed of rotation. An apparatus known as centrifuge is used which contains a centrifuge tube holder. Equal amount of solid-liquid mixture is present in the centrifuge tube holder.
As the rotor is rotated, due to the centrifugal force the denser insoluble particles separate from the liquid and ends up at the bottom of the tube. The liquid gets collected at the top.
Applications of centrifugation:
Separation of Cream from Milk: The process of centrifugation is used in diaries to separate cream from milk.
Used in washing machines to squeeze out water from clothes.
Used in laboratories to separate colloidal particles from their solutions.
Used in diagnostic labs for blood and urine test.
Separation by Sublimation:
Sublimation is the process of changing of a solid directly into vapour on heating, and of vapour into solid on cooling.
Sublimation is performed to separate components from a sublimable volatile component from a non-sublimable impurity by heating.
Ammonium chloride, iodine, camphor, naphthalene and anthracene can be separated from a mixture by sublimation.