Q. Why is gelatin mixed with gold sol?

 2100  185 Surface Chemistry Report Error

Solution:

Lyophilic sols are more stable than lyophobic sols.
This is due to the fact that lyophilic colloids are extensively solvated, i.e., colloidal particles are covered by a sheath of the liquid in which they are dispersed.
Lyophilic colloids have a unique property of protecting lyophobic colloids.
When a lyophilic sol is added to the lyophobic sol, the lyophilic particles form a layer around lyophobic particles and thus protect the latter from electrolytes.
Lyophilic colloids used for this purpose are called protective colloids.
Gelatin is a Lyophilic sol and when it is added to gold sol which is lyophobic sol it acts as a stabilizing agent by protecting the colloid.