If the gold number of potato starch is 25, how many grams of it is required to prevent coagulation of 100mL of gold sol on adding 10mL of 10% NaCl solution ?

The minimum no.of milligrams of protective colloid required to prevent the coagulation

of 10ml of gold sol by the addition of 1ml of 10% NaCl is called gold no.

10ml of gold sol  requires ----  25 mg of starch

100ml of gold sol  requires ----       ?

      =   250mg of starch(or) 0.25grams of starch