Coagulation is the process by which the dispersed phase of a colloid is made to aggregate…

Coagulation is the process by which the dispersed phase of a colloid is made to aggregate and thereby separate from the continuous phase.The minimum concentration of an electrolyte in milli-moles per litre of the electrolyte solution which is required to cause the coagulation of colloidal sol is called coagulation value.
Therefore higher is the coagulating power of effective ion, smaller will be the coagulation value of the electrolyte.
\(\text { Coagulation value } \propto \frac{1}{\text { coagulating power }}\)
The coagulation values of different electrolytes are different. This behaviour can be easily understood by Hardy-Schulze rule which states.
“The greater is the valency of the effective ion greater is its precipitating power.”
The coagulation of colloidal particles of the sol can be caused by: