Among the 21 375 experimental isotherms collected in the NIST-ISODB, the main adsorbates are nitrogen (5153), carbon dioxide (4366), hydrogen (2540), methane (2212) and water (607). Of particular interest for the present study are the experimental isotherms for nitrogen at 77 K (a total of 4003) and for argon at 87 K (a total of 140).