We extract the experimental pore volume from the average uptake (of nitrogen at 77 K or argon at 87 K) in the 0.6 bar to 0.8 bar range. Only a few characterization isotherms (29 over 860) were excluded because no pressure points were falling within this range. The Gurvich rule states that the density of the saturated nitrogen (or argon) in the pores is equal to its liquid density (ρ liq N 2 ; equal to 28.83 mol L -1 and 34.98 mol L -1 for nitrogen and argon, respectively), regardless of the shape of the internal void network or the chemistry of the crystal structure. Under this assumption, the pore volume (v pore ) of the adsorbent is computed as: