By Freundlich Adsorption Isotherm,
xm∝p1n
n > 1
xm is the extent of adsorption which means the amount of gas adsorbed by the adsorbent with pressure at constant temperature.
xm=k p1n....(1)
k and n are constants that depends on the nature of gas and adsorbent.
Taking log of equation (1) gives,
log (xm)=logk+1nlogP
Here, the factor 1n can have value between 0 to 1 based on the pressure range.
Freundlich isotherm holds good over a limited range of low pressure.
Hence, at low temperature, the isotherm is a straight line
∴ 1n=1
⇒xm=kp
Thus, the extent of adsorption linearly dependent on pressure.
At intermediate pressure,
0<1n<1
Hence,
⇒xm=k p1n
Thus, the extent of adsorption dependent on power of pressure.
At high pressure, the extent of adsorption attains a constant value and becomes independent of pressure.
Thus, 1n=0
⇒xm=k p0
⇒xm=k
Thus, extent of adsorption attains a saturation point.