Ferrioxalates

The most accurate solution actinometer currently available is the potassium ferrioxalate actinometer. Potassium ferrioxalate solutions absorb light in the range 250-509 nm. This broad range is both an advantage and a disadvantage since the solutions are sensitive to room light and must be carefully shielded from light until the intensity determination is made ... 

The products of the photodecomposition of the ferrioxalate absorb only weakly at wavelengths absorbed by ferrioxalate and therefore provide no problem with regard to a product filter effect. This can be seen from Table 2.7. 

The quantum yield for the potassium ferrioxalate actinometer as a function of wavelength is shown in Table 2.8. 

Lee and Sdiger 4 have estimated the error involved in the determination of the quantum yield for the ferrioxalate actinometer (at 365 nm) to be 2.5%. This then constitutes the minimum limit of error involved in the... 

The quantum yield of an actinometer may be affected by temperature. For potassium ferrioxalate this temperature effect is very small, as indicated in Table 2.9. 

A ferrioxalate actinometer was used to determine the lamp light intensity (12). The quantum yield of loss (4>d) and of product formation ( p) were then calculated by standard methods (12). 

A. W. Adamson, A. Vogler, H. Kunkely, R. Wachter. Photocalorimetry. Enthalpies of Photolysis of trans-Azobenzene, Ferrioxalate and Cobaltioxalate Ions, Chromium Hexacarbonyl, and Dirhenium Decacarbonyl. J. Am. Chem. Soc. 1978, 100, 1298-1300. 

Arslan, 1 Balcioglu, lA Bahnemann, D. Advanced chemical oxidation of reactive dyes in simulated dyehouse effluents by ferrioxalate-Fenton/UV-A and Ti02/UV-A processes. Water Research, 2001 37, 3061-3069. 

Ferrioxalates, actinometry, 1225 Ferrocene biosensors diacyl peroxides, 701... 

The method just described is not usually applicable in the ultraviolet because ultraviolet lamps of known spectral distribution are not readily available at present. The spectral sensitivity caii be calculated directly if the values of B L and P, are known. The first of these is obtained from the dispersion curve of the monochromator the second is somewhat difficult to measure—for prism instruments over restricted wavelength regions above 250 m t it is often reasonably constant. The photomultiplier sensitivity, P can be determined by comparison with a thermopile or with the ferrioxalate actinometer.11 12 Direct calculation of S, is subject to inaccuracies due to the accumulation of errors in the measurement of the three separate quantities B L and P,. A more convenient... 

The photodecomposition of ferrioxalate in 0.1N H2S04 (reaction (i)) is a Very useful chemical actinometer for the near uv and the visible region upto 400 nm ( 1.12)— ferrioxalate actinometer. In some low-valence hydrated cations, such transition may bring about photo-oxidation ... 

This result may be substituted into Eq. 15-40 to calculate Oir(A). Classical actinometers that are used in this way include the potassium ferrioxalate actinometer that can be employed both in the uv and visible spectral region the Reinecke s salt actinometer (visible region), and the ort/io-nitrobenzaldehyde actinometer (uv region). For further description of these actinometers we refer to the literature (e.g., Leifer, 1988, pp. 148-151). 

In Fe(II)/H202 acid media, oxidation occurs via hydroxyl radical. The use of ultraviolet in both cases results in the generation of HO radicals, formed by the reaction of Fe(II) with H202. In ferrioxalate systems, this reaction occurs after photolysis by photons with wavelengths less than 450 nm therefore, it plays a significant role in the degradation of organic pollutants in natural water, due to solar irradiation. 

Safarzaden-Amiri, A., Bolton, J.R., and Cater, S.R., Ferrioxalate-mediated photooxidation of organic pollutants in contaminated water, Water Res., 31(4), 787-798, 1997. 

Wilkinson s catalyst. Irradiation at 366 nm of 0.001 M RhCPPh NO and 1 M cyclohexene in o-dichlorobenzene was carried out under 1 atm H2 at room temperature. The hydrogen uptake was monitored using a mercury manometer attached to the reaction flask. Hydrogen was added periodically in order to maintain 1 atm pressure in the system. The solvent and olefin were distilled twice and degassed by three freeze-pump-thaw cycles before use. A 1000 watt Hg lamp filtered with a glass filter to isolate the 366 nm Hg line was used for all photolysis experiments. The light intensity, measured by ferrioxalate actinometry, was 1.0 x 10 6 einsteins/min. 

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