Separation of Mixtures

To separate different components of a mixture variety of physical techniques are available. All these separation techniques are based on difference in the physical properties of the components present in the mixture.

The following two factors decide the best possible technique to be adopted for separation:

  1. the type of mixture
  2. the component which you want to collect

1. Separating Funnels

The mixture of two immiscible liquids (the liquids that do not mix, as oil and water) can be separated by using a separating funnel. The mixture is placed in separating funnel and allowed to stand for some times. When the two layers of liquids are separated, the denser liquid which is in the lower part, is first collected by opening the stop-cock. This method is very useful in industries.

2. Evaporation

The separation of liquid (solvent) and solid (solute) from a solution is done by removing the liquid (solvent) by heating or by solar evaporation. By evaporation you can recover the solute component only in solid or powder form.

If the solvent is inflammable you cannot use flame for heating instead you can use an electrical heating system and an oil or water bath. Salt is obtained from sea water by the process of evaporation in shallow beds near the sea shore.

3. Filtration

Filtration is a better method for separating solids from liquids in heterogeneous mixtures. In filtration the solid material is collected as a residue on filter paper and the liquid phase is obtained as filtrate. The method of filtration is used on a large scale in industries.

4. Crystallization

Crystallization is a process of formation of solid crystals from a solution. The method of crystallization for separating solid from liquid begins by evaporating the liquid. However, in crystallization, the evaporation is stopped when the solution is concentrated enough. The concentrated solution thus produced, is allowed to cool slowly to form crystals which can be separated by filtration.

Mishri (sugar crystals) is produced by crystallization from concentrated sugar solution.

5. Distillation

The method of distillation is used to separate a liquid from a solution of a homogeneous mixture. The distillation is a process in which a liquid or mixture of liquids is boiled in a distillation flask. The vapour is condensed by passing through a water-cooled tube called condenser and collected as liquid called distillate.

In case of a solution of two miscible liquids (the liquids which can be mixed completely) the separation is based on the fact that the liquids will have different boiling points and there is a wide difference between the boiling points of the two liquids.

6. Magnetic Properties

In a mixture of magnetic and non-magnetic substances, the magnetic substance can be separated by using a magnet. For example, you can separate iron granules, which are magnetic, from non-magnetic substances like sand, sugar, or saw dust.

In industry, this method is used to separate iron materials from non-magnetic materials by using large electromagnets.