CBSE Class 12-science Answered

The protective power of the lyophilic colloids is expressed in terms of gold number a term introduced by Zsigmondy.

Gold number is the number of a milligram of the protective colloid which prevent the coagulation of 10 ml of red gold Sol When 1 ml of a 10 percent solution of sodium chloride is added to it.

 Thus, smaller the gold number of lyophilic colloid, the greater is the protective power

Reciprocal of the gold number indicates the protection power of a colloid.  

Both gold number and its protective power are inversely proportional hence smaller the gold number, more is the reciprocal, thus more is the protecting power of the protective colloid.