The protecting power of lyophilic colloidal sol is expressed in terms of

Lyophobic sols are unstable, so they are stabilised by adding some lyophilic colloids which protect them from precipitation. Thus, lyophilic colloids are called protecting colloids. Their protecting power is expressed in terms of gold number. In other words, gold number can be defined as the minimum amount of lyophilic colloid in milligrams, which prevent the flocculation of 10 mL gold sol by the addition of 1 mL of 10% NaCl solution.Note Lesser the gold number, higher is the protecting power.