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Gold Number is the amount (in milligrams) of a protective colloid which is just sufficient to prevent the coagulation of 10 ml of a standard hydro gold sol (which on coagulation changes from red to blue) when 1 ml of 10% NaCl solution is added to it.^[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

[1] ttps://books.google.com/books?id=V3VIaBDTpJ8C Physical Pharmacy

[1]

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	'''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.<ref>https://books.google.com/books?id=V3VIaBDTpJ8C Physical Pharmacy</ref>		'''Gold Number''' is the amount (in milligrams) of a protective colloid which is just sufficient to prevent the coagulation of 10 ml of a standard hydro gold sol (which on coagulation changes from red to blue) when 1 ml of 10% NaCl solution is added to it.<ref>https://books.google.com/books?id=V3VIaBDTpJ8C Physical Pharmacy</ref>

	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.		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.