Radiation Chemistry of Oxalate Solutions in the Presence of Oxygen over a Wide Range of Acidities

Abstract

The radiation yields of carbon dioxide, molecular hydrogen, and hydrogen peroxide formed were measured at 50 niM oxalic acid and 0.75 mM oxygen concentrations, over the pH range from 1.61 to 9.85. The results obtained are quantitatively consistent with a simple schenie which allows the determination of the primary free radical and niolecular yields in the pH region studied. A cube root dependence of the measured molecular hydrogen yields on oxalic acid concentration has been observed. . 0. Allen for his helpful suggestions and discussion of this work. Thanks are also due to 1VIrs. M. JIarovid and RIr. V. Jovanovid for their technical assistance in the experiments. (21) C. H. Cheek and V.

Tropospheric Aqueous‐Phase Free‐Radical Chemistry: Radical Sources, Spectra, Reaction Kinetics and Prediction Tools

“…= Competition kinetics; PNDA = p-nitrosodimethylaniline; NBE = nitrobenzene; CDNB = 1-chloro-2,4-dinitrobenzene; CDNBA = 4-chloro-3,5-dinitrobenzoic acid; PNP = 4-nitrophenol; * Herrmann [7] ; * NIST [6] ; & Buxton et al [3] are discrepancies for the available rate constants for oxalate monoanion ( Table 4). The rate constant measured by Ershov et al [32] for the oxalate mono-anion fit well in to the previously available data by Getoff et al [34] and Draganic et al [35] and appears to confirm the slower rate constants from the earlier studies. However, the older values and the more recent one by Ershov is significantly slower than the value reported by Ervens et al [36] measured at the same pH.…”

A Diffusion-Kinetic Model for Radiation-Chemical Transformations of Oxalic Acid and Oxalate Ions in Aqueous Solutions

“…The calculated yield of CO 2 was lower than the experimental value by approximately 15% only at a high concentration of oxalic acid. Although this difference does not significantly fall outside the limits of experimental error specified by Draganic et al [15], it is believed that the "increased" yield of CO 2 at oxalic acid concentrations higher than 0.2 mol/l is due to oxalic acid reactions in spurs.…”

“…Acid Solutions The radiolysis of oxalic acid (H 2 C 2 O 4 ) and its dissociation products ( and ions) has been studied in sufficient detail [1,[10][11][12][13][14][15][16][17][18]. The main radiolysis products of aqueous oxalic acid solutions are CO 2 , H 2 , H 2 O 2 , HCOOH, glyoxylic acid (HOOC-HCO), and tartaric acid (HOOC-CH(OH) 2 -CH(OH)-COOH).…”

“…The reaction scheme given below describes, as will be demonstrated in the subsequent text, the degradation of oxalic acid at low degrees of radiation-chemical conversion. The rate constants were borrowed from [2,[13][14][15][16][17]19].…”

“…To correct the rate constants of reactions (37)-(39), we used published data [15] on the buildup of H 2 , H 2 O 2 , and CO 2 at low oxalic acid conversions over the range of pH 1.4-9. We chose values that suited best for describing experimental data.…”