 On the other hand, heterogenous adsorption (multi-site) have a variable formula_5 of adsorption depending on the percent of sites occupied.When the adsorbate pressure (or concentration) are low, high energy sites will be occupied; and as the pressure (or concentration) increases, the lesser energy sites will be occupied resulting in a lower formula_5 of adsorption.Experimentally it was determined that extent of gas adsorption varies directly with pressure, and then it directly varies with pressure raised to the power 1/n until saturation pressure Ps is reached.