The Langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. At these conditions the adsorbate's partial pressure, , is related to the volume of it, , adsorbed onto a solid adsorbent. The adsorbent, as indicated in Figure 1, is assumed to be an ideal solid surface composed of series of distinct sites capable of binding the adsorbate. The adsorbate binding is treated as a chemical reaction between the adsorbate molecule and an empty site, . This reaction yields an adsorbed complex with an associated equilibrium constant