Abstract
1. The photo -sensitising oxides have been shown to
exhibit a 'fixation' of gaseous oxygen on
illumination with near U -V light. This reaction
was found to be specific for oxygen among the gases
investigated.
2. The method developed for the study of the photo - oxidation of plant pigments on thallous bromide has
been found to be unsuitable to the study of the
photo- oxidation of Chlorazol Sky Blue and Malachite
Green adsorbed on various sensitising oxides.
3. The correlation between the sensitising activity of
the various oxides and the various samples of TiO2
and their power of oxygen 'fixation' has been
demonstrated over a wide range.
4.The reaction with TiO₂ has been shown independent
of the presence of various impurities. No bulk
stoichiometric oxide was formed as a final product.
5. The production of a short-life highly-active
oxidising agent has been demonstrated but no
evidence of hydrogen peroxide was found when
considering Ti0₂.
6. Various physical parameters of the reaction between
oxygen and titanium dioxide were investigated. They
indicated that it was not a pure photo -chemical
reaction.
7. Zinc oxide was shown to behave in a manner similar
to that exhibited by TiO₂ with the exception of the
production of H₂0₂ in the presence of water.
8. The fading of Chlorazol Sky Blue, adsorbed on the
oxides, was demonstrated to be an oxidation reaction
occurring in vacuo and in oxygen. In the former
case, however, the reaction ceased long before
complet ion of total fading. The type of reaction
exhibited by Lialachite Green oxalate, adsorbed on
Ti0₂, appeared to differ from that reported for the
same dye sensitised by TlBr.
9. General reaction schemes have been proposed to
account for the main features of the photo- fixation
of the gaseous oxygen and subsequently the photosensitising effects of the various oxides.
10. The rapid oxygen uptake by various samples of
as Ti0₂ on illumination is proposed an analytical
method of determining small quantities of that gas
contained in inert atmospheres.
