The infra-red spectra of constitutional and terminal hydroxyl groups of biotite, muscovite, silica gel, alumina, silica-alumina and decationated Y-zeolite were measured between room temperature and 600°. Large changes in optical density and band half-width were sometimes observed. However, the integrated intensities showed little change with silica and silica-alumina and decreased by approximately 15% with the others. Although these latter results are not conclusive evidence for proton delocalization, they can be interpreted in this way.