Infrared spectra of hydroxyl groups on the surface of oxides generally consist of several absorption bands the number and relative intensity of which depend on the oxide nature and degree of dehydroxylation. This dependance is explicable on the basis that under high concentrations of surface hydroxyls the latter get involved in hydrogen-bonding interaction. However, even so-called “free” surface hydroxyls on some oxides give rise to more than one infrared absorption band.