Question

What happens when persistent dialysis of a colloidal system is carried out?

Answer 1

Hint: We know that presence of small amounts of electrolytes makes the colloid sol stable. Dialysis is a method which is carried out for the removal of electrolytes. It is a method of coagulation of the colloids.

Complete answer:
We know that a colloidal system is a solution where two substances of different phases are present. Here, very small particles of a substance called the dispersed phase or colloid are distributed through another substance which is the dispersion medium.
Before answering the question, let us understand what dialysis is.
In chemistry, dialysis is the process by which we separate suspended colloid particles from dissolved ions or molecules by their unequal rate of diffusion through a semipermeable membrane. It is basically a method of purification which removes the electrolyte particles or ions from the colloidal system.
Higher is the number of charged particles in a colloid system, higher will be its stability i.e. presence of electrolytes makes a colloid stable. Upon dialysis, the stability of the colloidal system is affected.
Upon dialysis we obtain pure colloidal solution which is neutral as all the ions are removed. Thus, the colloid coagulates and gets destabilised.
Thus, on persistent dialysis the colloid is destabilised and coagulates.

Note:
Persistent dialysis is a method that we use for coagulation of the colloid. There are other methods which can be used like electrophoresis and by mixing two opposite sols. By electrophoresis, the charged colloid particle moves to the oppositely charged electrode and gets discharged resulting in coagulation. In the next method, when we mix two oppositely charged sols they neutralise each other thus result in coagulation.