The Langmuir adsorption isotherm is deduced using the assumption:
(a) The adsorption takes place in multilayers
(b) The adsorption sites are equivalent in their ability to adsorb the particles
(c) The heat of adsorption varies with coverage
(d) The adsorbed molecules interact with each other
(b) The main points of Langmuir's theory of adsorption are as:
(i) Adsorption takes place on the surface of the solid only till the whole of the surface is completely covered with a unimolecular layer of the adsorbed gas.
(ii) Adsorption consist of two opposing processes (a) condensation, and (b) evaporation.
(iii) The rate of condensation depend upon the uncovered surface of the adsorbent available for condensation.