What is meant by coagulation of a colloidal solution ? Describe briefly any three methods by which coagulation of a lyophobic sol can be carried out.

Explanation

The process of settling of colloidal particular is called coagulation or precipitation of the sol.
Method of which coagulation of lyophobic sols can be carried our .
(i) By electrophorosis : The colloidal particles move towards opposite charged electrodes, electrodes get discharged and precipitated under an applied electric field.
(ii) By mixing two oppositelyl charged sols : Oppositely charged sols when mixed is almost equal properties, neutralise their charges and get partially or completely precipitated. Mixingof hydrated ferric oxide (+Ve sols) and aresenious sulphide (-ve sol) bring them is the precipitated forms. This typeof coagulation is called mutual coagulation.
(iii) By Boiling : When a solution is boiled, the adsorbed layer is disturbed due to increase colloisions with the molecules of dispersion medium. This reduce the charge on the particles and ultimately lead to setting down in the form of precipitate.