Can you please explain what is gold number(Protection of Colloids)?

The concept of gold number was introduced by Zsigmondy.It is a term used in colloidal chemistry.It is defined as-
‘Minimum amount of lyophilic colloid in milligrams which is required to prevent flocculation of 10ml gold sol by the addition of 1ml of 10% NaCl solution.‘
The coagulation of gold sol is indicated by change in colour from red to blue when particle size just increases.More is the gold number,less is the protective power of lyophilic colloid as it means that amount required is more.For ex-gold number of gelatin is 0.005 – 0.1, for haemoglobin it is 0.03 – 0.07.