Effects of temperatures, at which TiO2−x electrodes were prepared by thermal oxidation from titanium sheet metals, as well as platinum loading, on electrochemical and photoelectrochemical properties have been studied and the results are reported. Titanium dioxide electrodes prepared at higher temperatures were found to have slightly more negative flatband potentials and significantly higher donor densities than their low temperature counterparts. Platinum loading showed a similar effect to a lesser extent. Improved oxygen reduction kinetics and photoelectrochemical responses were observed at both the electrodes prepared at higher temperatures and platinum loaded TiO2−x electrodes; the oxygen reduction was affected by platinum loading more at oxide electrodes prepared at low temperatures than those prepared at high temperatures.

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Oxidation of -Octyl Mercaptan by Ferricyanide 1233 low values of s found, it would still be very desirable to perform a similar test with a solute of larger molecular weight, so that the full potential accuracy of modern ultracentrifuges could be realized.Two points which may confer advantage on the Rayleigh method of determining s by the Gutfreund-Ogston procedure must be mentioned in addition to those discussed earlier. These are: (i) the cylindrical lens magnification factor is not directly required, and errors in its equivalent, the fringe separation, are relatively unimportant; and (ii) as measurements are based on determining the positions of intensity minima, the results are independent of exposure time.Acknowledgments.-The author is greatly indebted to Professor J. W. Williams for his interest in, and critical comments on, this work, and to Professor L. J. Gosting for many discussions. The work was supported by a grant from the National Institutes of Health, No. A3030 (C6).