2085
RADIATION CHEWISTIRY O F OXALATE SOLUTIOXS
Radiation Chemistry of Oxalate Solutions in the Presence of Oxygen over a Vide Range of Acidities
by Z. D. DraganiE, I. G. DraganiE, and M. M. Kosanic Institute of Nuclear Sciences "Boris Kidrich," Vintcha, Yugoslavia
(Received December 27, 1963)
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.
It is often assumed that the radical and molecular products of the r-radiolysis of water, which are available to react with solutes 10+ sec. after the passage of ionizing radiation, can be represented by the following relation G-H~o--nw*
GH, GOH,Gn2, G H ~ o ~
(1)
where G denotes the corresponding radiation chemical yield. The true identity and structure of short-lived species, formed in the initial processes of the radiation decomposition of water and denoted as H atoms and OH radicals, are still a matter of discussion. Recent experiments on reducing species in water give an experimental evidence for the existence of hydrated electrons,'J while the existence of hydrogen atoms has been proved kinetically on many other occasion^.^ The nature of the oxidizing OH radical, especially in alkaline solutions, seems less certain. Therefore, GH and GoH in relation 1 represent the yields of H and OH species of their chemical equivalents. The yields in relation 1, which are also called the primary radical and molecular yields, have been thoroughly measured in acid media, especially in 0.8 N HzS04; it appears to be well known in neutral media as well.3 There are few complete data obtained on a single system for a high pH.4,5 Measurements on the same system in a large region of pH (acid, neutral, alkaline) are also still very rare.6-io The reason for this is the difficulty of choosing a suitable system; salts of metal ions are usually hydrolysed a t higher pH, whereas with organic compounds analytical chemistry
of the products formed in microquantities is often unsatisfactory or does not even exist. The scarcity of, and the discrepancy in, the results published so far moved us to carry out ineasureinents on one system in all three pH regions (acid, neutral, alkaline). The data we obtained in our previous work with aqueous oxalic acid solutions,ii,i2especially the complete material balance for acid medium in the presence of oxygen,13indicated that this system could be used. The results presented here cover the pH region from 1.61 to 9.85, while experiments at pH higher than this are in progress.
Experimental Solutions. The oxalic acid (H&z04.21-120)is an A.R. grade Merck product which was recrystallized before use. (1) G. Caapski and H. A. Schwara, J . Phys. Chem., 66, 471 (1962). (2) E. J. Hart and J. W. Boag, J . Am. Chem. Soc., 84, 4090 (1962). (3) A. 0. Allen, "The Radiation Chemistry of Water and Aqueous Solutions," D. Van Nostrand Co., Inc., New York, N. Y . , 1961. (4) h t . Haissinsky and P. Patigny, J . chim. phys., 59, 675 (1962). (5) M. Haissinsky, ibid., in press. ( 6 ) E. J . Hart, J . Am. Chem. Soc., 76, 4198 (1954). (7) F. S. Dainton and D. B. Peterson, Proc. Roy. Soc. (London), A276, 443 (1962). (8) F. S.Dainton and W. S. Watt, .Vature, 195, 1294 (1962). (9) M.Daniels and J. Weiss, J . Chem. Soc., 2467 (1958). (10) J. T. Allan and G. Scholes, Nature, 187, 218 (1960). (11) I. G. Draganid, J . chim. phys., 56, 9 (1959). (12) I. G. Dragani;, Nucleonics, 21, 33 (1963). (13) I. G. Draganid, J . chim. phys., 56, 16 (1959).
Volume 68, Number 8
August, 1964
2Q86
z. D. D R A G A XI.I ~G. , DRAG AN^, AKD 31. nI. K O S A K I ~
The water used was distilled in a continuous system, The dose rate was 2.3 X lo1$e.v. ml.-I hr,-I, deterfirst froiii alkaline permanganate, then from acid dimined by the Fricke dosimeter with G(Fe3+) = 15.5. chromate, and, finally, without any additive. No correction was introduced (
