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The Journal of Physical Chemistry, Vol. 8 3 , No. 16, 1979
cm-l, c is the molar concentration M, and 1 is the optical pathlength (cm). The initial reactant concentrations (To) were determined at 120 "C, reducing the number of unknowns by one since
To = [TI + [Dl + IN1 where the square brackets denote molar concentration. The spectra were digitized at the five wavelengths listed in Table I1 (i.e., i = 1-5) giving a set of five equations which were solved for C, by using the least-squares error matrix t e ~ h n i q u e .This ~ choice of wavelengths gave the minimal error and maximum sensitivity to changes in the reaction mixture. The data computations were performed on a Techtronics 4051 microprocessor. Analysis of the gas phase spectra of a synthetic reaction mixture indicated the mixture was 31.3% tetralin, 64.7% dihydronaphthalene, and 4.0% naphthalene. Gas chromatographic analysis of this mixture yielded 29.7 % tetralin, 67.1'30 dihydronaphthalene, and 3.2% naphthalene. To within the 5% error in the gas phase E values the two results agree and are representative of the accuracy of this optical analysis technique. Acknowledgment. This work was supported by the Division of Chemical Sciences, U.S. Department of Energy, Washington, D.C., under Contract No. EY-76-C-02-0016. References and Notes (1) T. Gangwer, D. MacKenzie, and S. Casano, J. phys. Chem., accepted for publication. (2) R. A. Morton and A. J. A. de Gouveia, J . Chem. SOC.,41 1 (1934). (3) R. A. Morton and A. J. A. de Gouveia, J. Chem. Soc., 916 (1934). (4) W. Huckel, E. Vevera, and U. Worffel, Chem. Ber., 90, 901 (1957). (5) L. Lapidus, "Digital Computation for Chemical Engineers", McGraw-Hill, New York, 1962, Chapter 7. Department of Energy and Environment Brookhaven National Laboratory Upton, New York 11973
T. Gangwer
Received March 12, 1979
Communications to the Editor
with HC1 and extracting the Os04into CC4. Osmium was determined colormetrically with thioureum by a method similar to that of Ayers and Wells.5 G(Os04 Os(IV)), hereafter referred to simply as G, was found to be 1.11f 0.05 for a 0.03 M NaOH solution containing about 1mmol of Os04per liter. Change of Os04in the range 0.6-5.6 mM did not cause an appreciable change in G, nor did a change of NaOH concentration from 0.03 to 0.06 M. The G value remained constant up to about 70% reduction, at least for millimolar OsO, solutions. After very long irradiations a precipitate of OsOz was observed. (In 0.4 M H2S04 reduction was negligible, i.e., G = 0.01. In alkaline solutions, which had been reduced by y irradiations, part of the Os(VII1) was regenerated over the course of hours after addition of an excess of acid.) The reduction of Os(VII1) to Os(1V) takes place in several steps. In this work intermediate formation of Os(V1) cannot be observed as it disproportionates to Os(1V) and Os(VII1) in acid solution. Os(V) and Os(VI1) likewise disappear by disproportionation in aqueous solutions and, if any Os(II1) were formed, it would be oxidated to Os(1V) by Os(V1). The reduction of Os04 is made possible by the evolution of 02.For this reason it is not surprising that the same G value is found for oxygenated and for deaerated solutions. The reduction of Os(VII1) to Os(1V) is too complicated a process to allow a definite interpretation on the basis of our present data. Although it is not impossible to give an example of a series of steps which would explain the observed G value, the lack of adequate thermodynamic data and of information regarding the reactions of Os(VII1) and possible intermediate states of Os would render such schemes speculative and of very limited value.
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Acknowledgment. We wish to mention a series of preliminary runs performed by Mr. G. Nooteboom. This work is part of the research program of the Institute for Nuclear Physics Research (IKO). made possible by financial support from the Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization for the Advancement of Pure Research (ZWO). References and Notes
Decomposition of OsO, in Alkaline Solution by y
Rays Publication costs assisted by the Institute for Nuclear Physics Research
Sir: The reduction of Os04 by y rays in alkaline solution occurs with an abnormal G value. Normally the number of equivalents reduced in alkaline solution is given by the equation G(red) = GH + G,- - GOH+ 2GHzO2 Examples are the reduction of iodate,2 manganate,3 and permanganate., It was found that this rule does not hold for the reduction of osmium tetroxide. To study the reduction of Os04 the solutions were irradiated by a radiocobalt source at an absorbed dose rate of 2.2 X eV mL- s-l. The osmium tetroxide was separated from the reduced osmium fraction by acidifying
0022-3654/79/2083-2178501 .OO/O
M. Hajssinsky, Actions Chim. B i d . Radiat., 164 (1967). M. Haissinsky, J. JovB, and W. Szymanski, J . Chim. Phys., 61, 572 (1964)1 M. Haissinsky and J.-C. Petit, J . Chim. Phys., 62, 222 (1965). B. Jezowska-Trzebiatowska and J. Kalecinski, Bull. Acad. Polon. Sci., S l r . Sci. Chim., 10, 241 (1962). G. H. Ayers and W. N. Wells, Anal. Chem., 22, 317 (1950). L. M. Dorfmann and G. E. Adams, Natl. Ref. Data Ser., Natl. Bur. Stand., No. 46, 42 (1973). E. J. Hart and M. Anbar, "The Hydrated Electron", Wiley-Interscience, New York, 1970, p 18. I. G. Draganic and 2. D. Draganic, "The Radiation Chemistry of Water", Academic Press, New York, 1971, p 142. Subfaculty of Chemistry University of Amsterdam Amsterdam, The Netherlands Institute for Nuclear Physics Research
A. H. W. Aten, Jr."
Johanna C. Kapteyn
WO) 1009 AJ Amsterdam, The Netherlands Received October 3, 1978; Revised Manuscript Received April 16, 1979
0 1979 American Chemical
Society
