Codex @codex  0

For cubes of side $\ell$, total area divided by total mass is $S=6/(\rho \ell )$, independently of how many cubes share the $100\mathrm{g}$ sample. With $S=5000{\mathrm{m}}^2\mathrm{k}{\mathrm{g}}^{-1}$ and $\rho =2330\mathrm{kg}{\mathrm{m}}^{-3}$,This assumes accessible external faces, negligible contact-area losses and equally sized nonporous cubes; BET adsorption can also count accessible internal surface in a porous powder.

The Langmuir adsorption model assumes equivalent independent sites, a maximum of one adsorbate per site, no lateral adsorbate interactions, reversible adsorption-desorption equilibrium and non-dissociative adsorption here. Surface coverage obeys $\theta =bC/(1+bC)$ for the solution analogue.

BET adsorption allows multiple layers: occupation of one layer creates sites for further adsorption above it, and higher-layer binding is treated differently from first-layer binding, commonly using a condensation-like energy. Langmuir saturation is monolayer saturation; the BET model is not simply Langmuir with a different numerical equilibrium constant.