Uranyl oxalate

Strongly) from a high intensity source. Uranyl oxalate, which has similar absorption characteristics to the complex (Sn2Cl o), was used for the actinometer. Quantum yields for the process were found to be 0.2. It was concluded that exchange occurs via an activated complex which is unsymmetrical. 

Uranyl oxalate actinometer. This actinometer has a range of 208-435 nm with an average quantum yield of about 0.5. Since the UO + ion acts as a photosensitizer for the oxalate decomposition the light absorption remains constant, but rather long exposures. re required for final accurate oxalate titrations. It is now mainly of histo al interest. 

Example of Application Large-Scale Actinometry. Neural network modelling was applied to large-scale actinometry in a continuous elliptical photochemical reactor with a concentric annular reaction chamber [2, 3,108, 148], Uranyl oxalate was used as an actinometer, which is based on the photosensitized decomposition of oxalate ions (Eq. 89) [2, 3] the experimental data were taken from the literature [108],... 

The purification of uranium by precipitation may involve the formation of insoluble oxalate or peroxide complexes.50 In the oxalate method the ore concentrate is dissolved in nitric acid to give a uranyl nitrate solution from which uranyl oxalate is precipitated according to equation (101), leaving the bulk of the impurities in solution. This approach is favoured over dissolution in hydrochloric acid and reduction to UIV prior to U(C204)2 precipitation since it is simpler and... 

Photocells may be used in place of thermopiles. Still other devices are chemical actinometers, which are merely gas mixtures or solutions sensitive to light. When radiation impinges upon these, a chemical reaction ensures whose extent is determined by the amount of energy absorbed. The most common of these is the uranyl oxalate actinometer, consisting of 0.05 molar oxalic acid and 0.01 molar uranyl sulphate (U02 S04) in water. Under the action of light following reaction take place ... 

Example The quantum efficiency after the decomposition of uranyl oxalate in an experiment was found to be 0.570 at 300 nm. When light was passed through an empty cell, decomposition of 6.201 10-3 mole of the oxalate took place in 2 hours. When the cell contained acetone and irradiation continued for 10 hours, 1.4 10-3 mole of acetone were decomposed and light not absorbed by acetone decomposed 2.631 10-2 mole of the oxalate. What is the Quantum efficiency for the acetone decomposition ... 

The reaction of uranyl oxalate has been applied for actinometric determinations [19,20]. 

One of the characteristic features of U02+ compounds is fluorescence, and uranyl oxalate is used as an actinometer. 

Kinetics in the irradiated system HI-NO have been studied by Holmes and Sundaram . They used 3130-3660 A radiation and a reaction cell temperature of 25 or 45 °C. Uranyl oxalate actinometry was employed. The photolysis of HI in this wavelength region produces hydrogen and iodine atoms which in turn react with either HI or NO. Holmes and Sundaram found that at 25 °C additions of NO significantly reduced the initial quantum yield of Hj. As the NO/HI ratio increased, the quantum yield fell to a limiting value. Additions of nitrogen to pure HI had no effect on the quantum yield. At 45 °C the reaction products were the same but the actinometry was irreproducible due to formation of ammonium iodide on the cell windows which reduced incident light intensities. 

The light intensity, studied in the reaction flask using uranyl oxalate as an acti-nometer, was determined with considerable accuracy. Relative light intensities are shown in Figure 2 in approximately the correct positions in the flask cross sections. The light intensity in the center of the flask is set equal to 1.00. 

Dehydration of uranyl oxalate trihydrate [77] proceeded through the monohydrate to the anhydrous salt which then decomposed ... 

If a high-purity product is not required, the procedure described here is an improvement over the earlier method,5 since the tedious operation to completely remove water (formed during the reduction of UO3) from the apparatus is avoided. Active U02 is obtained from anhydrous uranyl oxalate. The use of hydrogen gas during chlorination gives a clean reaction. These procedures give UCI4 that is sufficiently pure for most subsequent synthetic work. 

In the absence of chemical quenching, uranyl compounds have long luminescent lifetimes and high luminescent quantum efficiency [21]. Often, however, the excited state reacts chemically. The photochemistry of the ion, the most famous example of which is the uranyl oxalate actinometer, has generated an enormous body of work and been the subject of comprehensive reviews [22,23]. It can occur both in solution and in the solid state. The most common reaction is the oxidation of organic substrates. Both the photochemistry and the remarkable properties of the covalent bond, demand a satisfactory interpretation in terms of the electronic structure. 

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