Question

What is coagulation? Explain the Hardy and Schulze rules.

Answer 1

Coagulation is a process of aggregating together the colloidal particles so as to chnage them into large sized particles which ultimately settles as precipitate. It is generally done by addition of electrolyte. The ion which is resposible for neutralization of charge on the colloidal particle is called coagulating ion.

The quantity of the electrolyte which is required to coagulate a definite amount of a colloidal solution depends upon the valency of the coagulating ion(ion having a charge opposite to that of the colloidal particles). This observation of Hardy and Schulze is known as Hardy Schulze Law, the main points of which may be stated as follows:

(i) The effective ions of the electroyte in bringing about coagulation are thise which carry charge opposite to that of the colloidal particles. These ions are called coagulating ions or flocculating ions.

(ii) Greater is the valency of the coagulating or the flocculating ion, greater is its power to bring about coagulation.