The correct option is A Flocculation value
Flocculation value :
Flocculation value is the minimum concentration of electrolyte in millimoles required to cause coagulation of one litre of colloidal solution.
Flocculation value=Millimoles of electrolyteSize of particle volume of sol in litre
Gold number:
Gold number is the minimum amount of protective colloid in milligrams which when added to 10 mL of a standard gold sol just sufficient to prevent a colour change from red to blue on the addition of 1 mL of 10% NaCl solution.
Gold number=Weight of lyophilic sol in mg×10Volume of gold sol in mL
Protective power of protective colloids∝1Gold number
The power of the hydrophilic colloid to prevent the precipitation of a lyophobic colloid by addition of an electrolyte depends upon the nature of the substance, The protective character of various hydrophilic substance can be expressed quantitatively by gold number.