Gold number is associated with

To avoid the precipitation of lyophobic sol. by the addition of electrolyte, some lyophilic colloid is added to it. Such lyophilic colloid is called protective colloid and the action of lyophilic colloid by the electrolytes is known as protective anion. Gold Number Of a protective colloid is a minimum weight of it milligram which must be added to 10ml of a standard red gold sol so that no coagulation of the gold sol.