Abstract: The free radical intermediates produced under the illumination of aqueous dispersions of tungten oxide were detected by ESR combined with the technique of spin trapping.When solutions contained sodium acetate were irradiated, the ·CH₃ radical was detected. Whereas in systems containing sodium oxalate the ·CO₂^- radical was obse-rved. In systems containing potassium tartrate, the ·OH, ·CO₂^- and -OOCCOHCH-OHCOO^- radicals were identified.Experiments showed that irradiation of aqueous WO₃ dispersions gives rise to the formation of ·OH radicals. If appropriate substances are present, various other radicals can be generated as well. These are produced either by reaction with the ·OH radicals, or direct transfer of charge from the bands of the semiconducting material.

Key words: ESR spin trapping, free radicals, tungsten oxide