<P> Most industrial adsorbents fall into one of three classes: </P> <Ul> <Li> Oxygen - containing compounds--Are typically hydrophilic and polar, including materials such as silica gel and zeolites . </Li> <Li> Carbon - based compounds--Are typically hydrophobic and non-polar, including materials such as activated carbon and graphite . </Li> <Li> Polymer - based compounds--Are polar or non-polar functional groups in a porous polymer matrix . </Li> </Ul> <Li> Oxygen - containing compounds--Are typically hydrophilic and polar, including materials such as silica gel and zeolites . </Li> <Li> Carbon - based compounds--Are typically hydrophobic and non-polar, including materials such as activated carbon and graphite . </Li>

The curve showing the variation of adsorption with pressure at constant temperature is called