Oct., 1935
THEPHOTO-OXIDATION
OF
[CONTRIBUTION FROM THE CHEMISTRY
HYDROGEN A N D DEUTERIUM IODIDES
LABORATORY OF THE UNIVERSITY OF
17T3
MICHIGAN]
The Photo-oxidation of Hydrogen and Deuterium Iodides' BY G. A. COOKAND J. R. BATES Many investigations2 have been made of the reaction of hydrogen atoms with oxygen molecules. One such study was that of Bates and L a ~ i nwho , ~ obtained the hydrogen atoms for the reaction by the photo-dissociation of hydrogen iodide. It was pointed out by Bodenstein and Schenk4that the results of Bates and Lavin might be equally well explained on the assumption that the reaction H+Os occurred as either a two-body or a three-body process. The present work represents an attempt to differentiate between these two alternatives by studying the same reaction with improved experimental accuracy and under much more widely varied conditions. The problem is of theoretical importance in connection with the interpretation of a number of different reactions2such as the explosion limits of hydrogen and oxygen,; the effect of oxygen on the photochemical hydrogen-chlorine r e a ~ t i o netc. ,~ The general theoretical implications of the problem have been discussed by Kassel.'j A similar study was also made on the reaction of deuterium iodide with oxygen. A comparison of the results for hydrogen and deuterium iodides is of interest in connection with the effect of mass and zero point energy on chemical reactions.'
The hydrogen iodide was synthesized by passing a mixture of hydrogen and iodine vapor through a tube containing two glowing platinum spirals, the first spiral being kept hotter than the second. Deuterium iodide was made in a similar way, using deuterium obtained by electrolysis of 99.9% DzO. No stopcocks were employed in connection with the reartion vessel or the storage tube for hydrogen iodide; instead, two greaseless valves were employed. These made use of a glass bellows similar to that of Bodenstein,9 brit substituting for his glass-in-glass seat a fused silver chloride seat as described by Ramsperger.'o The hydrogen was analyzed by a method suggested by Professor H. N. Alyea of Princeton. It made use of a sensitive slanting mercury manometer, calibrated for the purpose, to measure the decrease in both pressure and volume resulting from the combustion of hydrogen in a sample of known volume. The rest of the apparatus was essentially the same as that described by Bates and L a v h 3
Experimental Results Results of the runs are incorporated in the tables. TABLEI RUNSMADEWITH HYDROGEN IODIDE AND OXYGEN HIo
200. F 200.5 199.9 150.e 150.6 Method and Apparatus 151.3 The method used was similar t o that of Bates and L a ~ i n . ~ 160.2 151.4 A mixture of hydrogen (or deuterium) iodide with oxygen 150.9 (and also in a few cases with nitrogen) in a quartz reaction 100.6 vessel of 277.1 cc. effective volume, was illuminated, thc 99.9 pressure change was noted and the products analyzed for 98.3 hydrogen and iodine. The reaction vessel was kept at 101.0 0" except in two 20' runs. The source of light was a low50.0 voltage mercury-argon quartz lamp designed by Duffen4 9.8 It used a nickel cathode activated by a dack and Owens.8 50.2 coating of barium and strontium oxides. .iO. 0 (1) (a) The material in this paper comprises a portion of a thesis XI. 2 presented b y Gerhard Albert Cook t o the Graduate School of the 50. 1 University of Michigan in partial fulfilment of the requirements for the degree of Doctor of I'hilosophy, 1935. (h) Presented before the .0 Division of Physical and Inorganic Chemistry a t the New York 50.2 Meeting of the American Chemical Society, April 22-26, 1!)35. ( 2 ) (a) tcor refercnrw w e R a t v s . J . Chem. P h y s . , 1, 457 (l!X33); phgsik. Clrern., 817, 1 1 1 (1!334i Ht!i J O l J M z i A l . , 56, 81 (1!1;3:3). errk, Z.p h g s i k . Chrm., BZO, J"0 ( 1 ( 5 , Ktlrsei ancl Storcti. paper presented before the Di l'liysical i l i r t l Itiorgaiiic Chrnristry a( the New York hfreting- of the American Chemical Society, April 22-26, 1935. (6) Kassel, in "Annual Survey of American Chemistry," Chemical Catalog Company. Xew Jlork, 1834, Vol. V I I I , pp. 27-30. (7) Eyring, J . Chem. Phys., 3, 107 (1935). ( 8 ) Unpublished paper.
Initial oxygen
H I decomposed
506. 4 449.9 400.7 581.1 550.0 449.2 450.0 350. A 382.5 601.3 608.8 499.5 451.1 699.4 700.7
36.57 37. 15 41.92 41.56 44.44 32.38 35.19 :XI. 23
ADO. :i 602. 1
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32.9F 35.41 40.48 27.86 37.95 41.07 34,:34 30. 01 3u.42 :30. 21 32.82 23.38 ,,-
=
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formed
kdkP
14.84 15.20 17.39 13.22 16.99 13.57 13.88 14.89 14.15 11.64 13.19 9.64 14.40 7.07 6.19 A . S.3 6.94 7.47 '7.89 G . 89 IO.;%!
0.084 ,090 ,092 ,086 .072 .058 ,079 ,070 ,063 . 0'72 ,069 ,076 057 ,077 ,081 . 068 ,067 070 ,070 . 077
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(9) Bodenstein, %. phvsik Chem., B7, 387 (1930). (10) Ramsperger, Rev. Sci. Instruments, P, 738 (1931)
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1 .20 1 . 53 1.56 1.25 1.05 0.98 1.34 1.42 1.27 1.04 1 .00 1.28 1.06 1 . 03 1.10 1 .OT 1 .oc, 1 .:
