The quantity of the electrolyte which is required to coagulate a definite amount of a colloidal solution depends upon the valency of the ion having a charge opposite to that of the colloidal particles. This observation of Hardy and Schulze are known as Hardy Schulze law.
Dialysis:It is a process of removing a dissolved substance from a colloidal solution by means of diffusion through a suitable membrane.
Since particles ions or smaller molecules) in a true solution can pass through animal membrane (bladder) or parchment paper or cellophane sheet but not the colloidal particles, the membrane can be used for dialysis.
A bag of suitable membrane containing the colloidal solution is suspended in a vessel through which fresh water is continuously flowing. The molecules and ions diffuse through membrane into the outer water and pure colloidal solution is left behind.
