Interactions redox titration

The bottom line quantitative distance data are hard to get from dipolar interaction data, but qualitative or topological information can be obtained. It is usually helpful to study spectra from intermediate redox-titration samples and/or spectra taken at different microwave frequencies. 

The loading of MnOx on the CeOz-ZrOz supports increases the specific surface areas (Table 1). It is important to point out that there are CeOz-MnOx interactions on unsupported as well as on supported catalysts. Using cerimetric redox titration [16] it was found that in comparison to the unsupported MnOx an increase of the Mn oxidation number is observed for CeOz-MnOx samples calcined at low temperatures, whereas a decrease was observed at higher calcination temperatures [15]. The obtained results are in accordance with those of Imamura et al. [16]. TPR measurements on MnOx/CeOz-ZrOz samples revealed that CeOz incorporation in the ZrOz structure leads to a small shift of the low temperature reduction peaks of MnOx phases to lower temperature thus, the presence of Ce ions in the ZrOz structure enhances the reducibility of the MnOx species. 

We have investigated the electron acceptor region of PS2 using inhibitors, herbicides and redox titrations [9,10]. The experiments used the epr signals from Q >i Fe, QB"Fe, I ", Cyt b559, non-haem Fe= and the interactions between them. We also used optical techniques to follow the redox dependence of the us and ms reduction of P680. 

In the final step of the analysis, the iodine is titrated with thiosulphate. The iodine is reduced to iodide, and the thiosulphate in turn is oxidized to the tetrathionate ion. The concentration of the thiosulphate solution used for the titration must be known precisely. The endpoint of the redox titration is commonly indicated by a starch indicator or by photometric or amperometric endpoint detection. The starch indicator forms an enclosure compound with iodine. The large electron cloud of the iodine interacts with the hydroxo dipoles in the starch helix resulting in an intensely blue colour of the iodine starch complex. Nevertheless, the iodine molecules can leave the starch hehx easily and thus can be reduced by thiosulphate. The endpoint of the titration is clearly marked by the change from blue to colourless. 

In general, titrations governed by precipitation reactions do not really constitute an appreciable number in volumetric determinations in comparison to either redox or acid-base reactions. The interaction between silver-nitrate and sodium chloride in solutions result into the precipitation of silver chloride as shown below ... 

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