Gold number
Gold Number is the amount (in milligrams) of a protective colloid which just prevents the coagulation of 10 ml of a standard hydro gold sol (which on coagulation changes from red to blue) on adding 1 ml of 10% NaCl solution.[1]
Coagulation of gold sol is indicated by colour change from red to blue/purple when particle size just increases. More is the gold number, less is the protective power of the lyophilic colloid since it means that the amount required is more. It was first used by Richard Adolf Zsigmondy. The amount is taken in terms of weight in milligrams.
The gold number of some colloids are given below.
| Protective Colloids | Gold Number |
|---|---|
| Gelatin | 0.005-.01 |
| Haemoglobin | 0.03-0.07 |
| Egg Albumin | 0.15-0.25 |
| Potato Starch | 20-25 |
| Gum arabic | 0.15-0.25 |
| Caseinate | 0.01-0.02 |
| Sodium Oleate | 1-5 |
| Dextrin | 125-150 |
References
- ^ https://books.google.com/books?id=V3VIaBDTpJ8C Physical Pharmacy