The particles of colloidal solution possess electrical charge which is responsible for the stability of these solutions. The charge on colloidal particles arises because of selective adsorption of ions which are common with their own lattice. The presence of charge on colloidal part!cles can be determined with the help of phenomenon known as electrophoresis. However, when some electrolyte is added, the charge on the particles of dispersed phase gets neutralized and precipitation takes place. This process is also called coagulation. The coagulation is given by Hardy Schulze rules. According to these rules the ions carrying the charge opposite to that of sol particles are effective and coagulating power of an electrolyte is directly proportional to the fourth power of the valency of the ion. Coagulation can also occur by mutual precipitation, by electrophoresis, by persistent dialysis or by heating or cooling.
Which charge is responsible for stability of colloidal particles ?