ADSORPTION ISOTHERM (with reference to Fig.4.7)

• ‘M’ represents amount adsorbed at equilibrium.
• In region ‘1’ adsorption follows a linear path.
• In region ‘2’, saturation has almost been reached and monolayer adsorption has occurred.
• In region ‘3’ bulk condensation starts.
• The dotted curve represents the porous medium where most of the pores are of same radius . A jump is observed at the pressure when all of these pores are filled up.



Fig:4.7: Saturation curves for non porous material(solid curve) and for material with almost constant pore radius (dotted)

Hysteresis
When a filled pore is emptied, it does not follow the same path as it did during filling and a hysteresis loop is observed. If pore radius distribution is uniform then this curve also would be smooth (there won’t be a sharp rise and fall)