Question

How to calculate a gold number?

Answer 1

Hint: a measure of the protective power of a lyophilic colloid expressed as the amount of the dry material that just protects a red gold sol under specified conditions — compare protective colloid. Coagulation of gold sol is indicated by a color change from red to blue/purple when particle size increases.

Complete answer:
The gold color number is defined as the number of measures of efficiency to protect a colloidal solution from precipitation. If the gold number value is smaller, then the protective power of the colloid will be higher. The coagulation of gold sol increases in particle size, indicated by a color change from red to blue or purple. The best protecting colloid is gelatin as it has the lowest gold number.
The gold number is calculated by knowing the number of milligrams of protective colloid which is sufficient to prevent the coagulation of 10 ml of standard gold solution when 1 ml of 10% solution of sodium chloride is added to it.
\[Gold{\text{ }}number{\text{ }}\propto \dfrac{1}{{Protective{\text{ }}power}}\]
This concept of gold number was given by Zsigmondy. It is an experimentally determined quantity.
A colloidal solution is a mixture in which the substances are regularly suspended in a fluid. Stable colloids are also known as lyophilic sols, in which strong forces of interaction exist between the dispersed phase and the dispersion medium. These are prepared by the following suitable methods.

Note:
There are many examples of a colloidal solution or colloids. Blood is one of the common colloid solutions found in our bodies. Blood contains a respiratory pigment that has albumin protein in water. The pigment part contains albumin that acts as the dispersed phase and the dispersion medium is water. It is a hydrosol.