ADDITIONS AND CORRECTIONS
766 of a recent finding,' which indicates that in pure HC1 ion neutralization does not contribute to Hz formation. (7) R. A. Lee, Nature, 216, 58 (1967), (8) Chemistry Division, Argonne National Laboratory, Argonne, Ill. 60439.
LABORATORY OF RADIATION CHEMISTRY SCHOOL OF CHEMISTRY THEUNIVERSITY UPON TYNE, 1, ENGLAND NEWCASTLE
G. R. A.
JOHNSONS
J. L. REDPATH
RECEIVED DECEMBER 4, 1967
Activation Energies for Reactions of
the Hydrated Electron Sir: It has been stated recently that the lowest activation energy for reactions of the hydrated electrons, eaq-, is that for diffusion in water, Le., 3.5 kcal mole-'. An unfortunate misprint quoted our value for the eaqNO2- reaction wrong1y.l We have measured the temperature dependence for the reactions of hydrogen ions, H+, and nitrite ions, NO%-,with eaq-. The reagents used were HC104 and NaNOz Analar grade (Hopkin and Williams Ltd.). The pulse radiolysis technique2i3was used and the rate of disappearance of the eaq- at 650 nm after a pulse of about 10 rads was measured. In repeat observations, the rate constants at 20" were found to be k(eaq- H+) = 2.2 X 1Olo M-' sec-l and k(eaqNOz-) = 3.2 X lo9 M-1 sec-1, in agreement with previously reported
+
+
+
values.' Under our experimental conditions we were able to control the temperature over the range from 20 to 80" within f1". The activation energies calculated from Arrhenius plots were found to be for the reactions eaq- with H+ and NOz- 2.6 and 1.7 kcal mole-', respectively, the uncertainty being smaller than f10%. These values are substantially lower than the activation energy for diffusion in water.' The mechanism by which eaq- are transferred through water is therefore likely to be different from normal diffusion. It also excludes any other process with an energy requirement significantly in excess of 1.7 kcal mole-', such as dipole reorientation of water molecules which requires about 4 kea1 m01e-l.~ Acknowledgment. The data reported belong to a series of experiments carried out in collaboration with Dr. A. 0. Allen and Dipl. Ing. K. U. Willamowski at the Paterson Laboratories. (1) M. Anbar, E". B. Alfassi, and H. Bregman-Riesler, J. Am. Chem. SOC.,89, 1263 (1967). (2) J. P.Keene, J. Sci. Instr., 41,493 (1964). (3) J. P. Keene, "Pulse Radiolysis," M. Ebsrt, J. P. Keene, A. J. Swallow, and J. H. Baxendale, Ed., Academic Press, London, 1965, P 8. (4)M.Anbar and P. Neta, Intern. J . Appl. Radiation Isotopes, 16,227 (1965). (5) C. H. Collie, J . B Hasted, and D. M. Ritson, Proc. Phya. Soc., 60, 147 (1948).
PATERSON LABORATORIES B. CERCEK CHRISTIE HOSPITAL AND HOLTRADIUM INSTITUTEM. EBERT MANCHESTER 20, ENGLAND ACCEPTED AND TRANSMITTED BY THEFARADAY SOCIETY (SEPTEMBER 26, 1967)
A D D I T I O N S AND C O R R E C T I O N S 1967, Volume 71 L. R. Romsted, R. Bruce Dunlap, and E. H. Cordes: Secondary Valence Force Catalysis. V. Salt Effects on Certain Detergent-Catalyzed Organic Reactions. Page 4581. Through no fault of the authors, the communication contains the incorrect designation of methyl orthobenzoate as methyl o-benzoate.-THm EDITORIAL STAFF.
The Journal of Physical Chemietry
