text: Li Zhou and coworkers used a volumetric apparatus to measure the adsorption equilibria of hydrogen and methane on activated carbon (Figure 2, 3). They also measure the adsorption equilibria of nitrogen on microporous activated carbon (Figure 4) and on a mesoporous silica gel (Figure 5) for both subcritical and supercritical region. Figure 6 shows the isotherms of methane on silica gel.