Question

What is coagulation? Explain.

Answer 1

Coagulation is a term that is used in the case of colloids. The settling down of colloidal particles on the removal of repulsive forces between them is called precipitation or coagulation of colloids.

Complete step by step answer:
Colloids are mixtures of particles with their diameter or dimension ranging from $1$ to $1000$ nanometres. Even though the particle size is much larger, they remain dispersed in a dispersion medium. The reason for this is the charge on colloidal particles. All colloidal particles carry a charge. This prevents the particles having the same charge from coming together and thereby precipitate. Hence the colloidal particles repel each other. This repulsive force is the reason for the stability of colloids. When this charge is removed by some means, the particles come together and finally settle down. This process is called coagulation.
Coagulation of colloids can be achieved by the following methods.
1.By mixing two oppositely charged colloids.
2.By the addition of suitable electrolyte.
3.By a process called electrophoresis. In this process, the colloidal particles move towards opposite charged electrodes, get neutralised and coagulated.
4.By repeated dialysis.
5.By boiling.
6.By addition of suitable solvents.
7.By continuous shaking.
The nature of the colloids determines in which method they can be coagulated.

Note: There are two types of colloids – lyophilic colloids and lyophobic colloids. Coagulation of lyophilic colloids are not easy compared to that of lyophobic colloids. Because lyophilic colloids are more stable due to high solvation of colloidal particles. There exists a strong interaction force between dispersed phase and dispersion medium in the case of lyophilic colloids.