CAPILLARY CONDENSATION

As it’s was proved earlier that for condensation super saturated vapor is required.
However, in presence of small corners or pores, we can observe this phenomenon even if the vapor is under-saturated.
Suppose a pore is present
Here meniscus is assumed a part of the sphere i.e. part of a vapor bubble.

If bubble would be in chemical equilibrium.

So here, bulk condensation is not possible since vapor is under saturated but capillary condensation is possible.
For porous material, much of the material is absorbed by capillary condensation.
The agglomeration of suspended particles and aerosols is also explained by capillary condensation.

Consider two spherical particles in contact (Fig 4.6)

       Fig:4.6: