Localized Adsorption of N 2 on Sublimed Cadmium Bromide and Real Surface Area

The adsorption-desorption of N₂ at 77.5 K on a sublimed sample of cadmium bromide has been studied. The ideal isotherm is applied to experimental data to determine surface area independently of a BET plot. The Frenkel–Halsey–Hill (FHH) plot indicates that there is a localized adsorption of the nitrogen molecules in the monolayer and that at p/p₀ ≥ 0.4 the multilayer adsorption proceeds in a normal way. In order to obtain the real surface area of the sample from the BET's Vm a cross-sectional area equal to 0.178 nm²/N₂ molecule should be used.