Acetic acid is added in the process of coagulation.
The conversion of a sol into a precipitate is known as coagulation. It involves the neutralization of a sol particle to form a suspension and this represents the coagulation.
The process of coagulation can be carried out in the following ways:
1. By electrophoresis: In this method, the colloidal particles are forced to move towards the oppositely charged particles, and then they are discharged and collected at the bottom.
2. By mixing two oppositely charged sols: In this type of coagulation equal amounts of oppositely charged particles are mixed, they cancel out their charges and then precipitate.