Question

The protective action of colloids is compared in terms of:
A. oxidation
B. gold number
C. Reynold number
D. no option

Answer 1

Hint:To answer this question we should know what protective action means. We should also know the meaning of oxidation, gold number, and Reynold number. The protective power of a colloid is the milligram amount of protective colloid required to prevent the coagulation of lyophobic colloids.

Complete answer:
The lyophilic colloids are stable but lyophobic colloids are unstable. They coagulate easily. So, the lyophilic colloids are added to the lyophobic colloid. The lyophilic colloid makes a layer around the lyophobic colloid and thus protects the lyophilic colloid.
This is known as the protection of colloids. The lyophilic colloids are known as protective colloids.
When hydro gold sol is mixed with sodium chloride solution it coagulates. The minimum amount in milligram of protective colloid required to prevent the coagulation $10$ mL of hydro gold sol is known as a gold number.
So, the protective action of colloids is compared in terms of gold number.

Therefore, option (B) gold number is correct.

Note: Higher the gold number lower will be its protecting power. Lyophilic colloids are liquid loving means dispersed phase easily interacts with the dispersion phase, so they can easily form by mixing. Lyophilic colloids are reversible colloids. Lyophilic colloids are stable. They do not coagulate so, do not require a stabilizer.Lyophobic colloids are liquid haters, so the dispersed phase does not interact easily with the dispersion phase, so they can be prepared by special methods only. Lyophobic colloids are irreversible colloids. Lyophobes require stabilizers because they coagulate easily.