Question

What does Hardy Schulze rule state?

Answer 1

The Hardy Schulze rule is based on the effect of magnitude and sign of the ions present in an electrolyte that are responsible for carrying out the coagulation process. Similar to neutralization, opposition charges are needed to discharge the sol particles.

Complete answer:
Coagulation also known as precipitation is a process in which colloidal particles or the discharged sol particles come closer to one another and begin to aggregate so as to transform into large sized particles and finally settle down at the bottom of the container as a precipitate.
Charged species called electrolytes are responsible for carrying out the process of coagulation. Colloidal particles or sol particles contain a specific charge on them which needs to be removed. This charge removal or the process of neutralization of charge on the colloidal particles is performed by the aid of a specific set of ions known as coagulating or flocculating ions.
Hardy Schulze was a scientist who worked on the properties of colloidal solutions and observed the effect of addition of electrolytes on different colloidal particles.
The Hardy Schulze rule states the following:
The ions of the electrolyte that are effective in bringing about a significant coagulation effect should carry a charge opposite to that of the colloidal particles being neutralized. These ions are therefore labelled coagulating ions.
The coagulating effect or flocculating effect is directly proportional to the magnitude of charge or valency of the coagulating ions. Ions with higher valency or higher charge tend to show a greater coagulating effect.

Note:
The charge of specific ions that bring about coagulation or the flocculation process only depends upon the sign and magnitude of charge present on the colloidal particles and is independent of other factors like temperature and solvent.