Actinometry uranyl oxalate

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],... 

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. 

Accordingly, we determined the quantum yield of the photohydrate of 1,3-dimethyluracil (DMU) for initial DMU concentrations of 1 X 10-3M, and 1 X 10-4M in unbuffered triple-distilled water. The measurements were made according to the conventional double cell technique (12), using uranyl oxalate as the actinometer. In this method, the total number of incident and transmitted quanta are measured by chemical actinometry. The quantum yield for DMU disappearance was found to be 3.93 X 10-3 at 1 X 10-4M DMU and 3.79 X 10-3 at 1 X 10-3M DMU (single determinations), and is thus independent of concentration in this range. 

A mixture of a uranyl salt e.g. nitrate and an excess of oxalic acid (giving mainly uranyl oxalate) is one of the earliest and better studied systems for actinometry. The rate of disappearance of oxalic acid on irradiation is easily determined by titrating an aliquot of the solution and repeating the titration after exposing an identical aliquot to the same light source used for the photo-reaction and under identical conditions, to those used in the reaction under study. 

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