oxides was studied. Two main types of acetylene adsorption complexes were found: first, complexes formed by weak reversible adsorption at O 2À sites and basic OH groups and, second, stable complexes formed by the dissociative adsorption of acetylene at Me d+ -O dÀ pairs with the formation of acetylide species. The position of the C-H band in weakly adsorbed complexes and C= =C bands in strongly adsorbed complexes can be used for the sensitive characterization of oxide basicity. The measurements performed at elevated acetylene pressures (10-20 Torr) give information on the total basicity of oxides, whereas the analysis of the complexes formed at low pressures ($0.2 Torr) characterizes the properties of specific absorption sites. The interaction of acetylene with surface sites was mainly reversible; however, the products of acetylene oligomerization could be observed in the long-term experiments.

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