In the capillary condensation region, the isotherm generally shows hysteresis so that the apparent equilibrium pressures observed in adsorption and desorption experiments are different (Figure 2). The desorption branch is always at lower fugacity and pressure. The hysteresis begins at P/P₀ = ~0.6, where capillary condensation begins to dominate the adsorption process, although the pore size distribution algorithm uses the entire isotherm. The calcu

The method of measurement and calculation presented here is the gold standard in porosimetry. The mercury porosimetry technique is an alternative, but its high pressures and possibility of exposure to mercury are disadvantages. Better pressure transducers, vacuum pumps, and software have greatly extended the utility of N₂ porosimetry, and the method gives all 3 key adsorbent or catalyst morphological measurements (A, pore volume, pore size distribution) in one experiment. It also provides info