2152
JAMES
E. CLINEAND GEOKGE S. I'OKUES
Vol. 63
'l'he value found for A is 8.8 and u = I.;{ A. The value found for the activation energy and the effective collision diameter are in accord with those found by Elliott and Sugden12 in their studies of bromide exchanges in a series of alkyl bromides. Acknowledgment.-The apparatus used in this research was built with the aid of a grant from the Research Corporation.
3.0 I-
I
0.2 -
\ I u 271
281
291
301
( 1 / T ) X 1P. Fig. 2.
activation energy the parameter A of the modified Arrhenius equation k E logA --
di-
4.57T
may be evaluated and in turn the effective collision diameter can be calculated from
[CONTRIBUTION FROM T H E CHEMICAL
Summary The exchange of bromide ions with a-bromopropionic acid was studied in aqueous solution and the activation energy was determined. The reaction obeyed the Arrhenius equation to within experimental error and the value of the effective collision diameter was found to be about what would be expected from simple collision theory. The values of the activation energy and collision diameter are in accord with other similar work. (121 G. A. Elliott and s. Sugden, J Chem. S O C . , 1836 (193'2) BALTIMORE, MARYLAND
RECEIVED MAY19, 1941
LABORATORY O F HARVARD UNIVERSITY]
Rates of Reaction of Excited Mercury with Oxygen, Hydrogen Sulfide and Nitrous Oxide, and their Relation to Effective Collision Diameters BY JAMES E. CLINEAND GEORGES. FORBES
-
Introduction.-This investigation was undertaken to correlate the quantitative dependence of reaction rate on pressure with effective collision diameters in reactions involving mercury excited by resonance radiation. Effective collision diameters have been estimated through studies of the quenching of mercury fluorescence by various gases. Of numerous papers a few may be Z e m a n ~ k ycorrected ~,~ his results for reabsorption of fluorescence radiation. Franks concluded that reaction rate is proportional to intensity of resonance radiation (A = 2337 8.1 and that radiation of wave length less than 2000 A. is without influence upon the reaction. His further conclusions are discussed below. Leipunski and Sagulin6 had shown that this reso( 1 ) Stern a n d Volmer, Physik. Z . , 20, 183 (1'219). ( 2 ) S t u a r t , Z. P h y s i k , 33, 202 (1925). (3) Zemansky, P h y s . Rev., 31, 812 (1928). ( 4 ) Zemansky, i b i d . , 36, 919 (1!):3lJ). ( 6 ) F r a n k , AckzPhysicochim. (17. S. I
