FRANCESCO PAOLO CAVASINO
1378 rium between monomers and solvated electrons for the alkali metals is essentially the same for tetraalkylammonium cations, some solutions should have contained at least 60% of the electrons as monomers. Moreover, the monomers, if they are formed containing tetraalkylammonium cations, should contain cations with widely differing geometrical requirements which should be reflected in the spectra of these solutions. Making the reasonable assumption that our solutions contain a significant fraction of electrons as YR4 monomers, the spectral data suggest that in the relatively dilute concentration range (2-200 X 10-5 M )
the solvated electron is not associated with the solvated cationic species in solution in the manner required by the “expanded-metal” model.6-8 Rather the results seem to favor the “cavity model”2-6 in which the trapped electron is electrostatically associated with the solvated cations presentj30 much as is any ammonia solution containing charged species.31 Acknowledgment. We gratefully acknowledge the financial support of the Robert A. Welch Foundation and the National Science Foundation. (31) V. F. Hnizda and C. A. Kraus, J. Am. Chem. Soc., 71, 1565 (1949).
A Temperature-JumpStudy of the Kinetics of the Formation
of the Monosulfato Complex of Iron(II1) by Francesco Paolo Cavasino Institute of Physical Chemistry, Unbersity of Palermo, Palermo, Italy Accepted and Transmitted by The Faraday Society
(May 26, 1067)
The rate of formation of the monosulfato complex of iron(II1) has been studied in acidic aqueous solution at 25” and ionic strength of 1.2 and 2.0 M and in the temperature range of 7-33’ at ionic strength 0.5 M. Over the range of acidity studied at p = 0.5 M (0.01 M 6 [H+] 0.41 M), the complex formation occurs significantly via two paths: Le., an acid-independent path and a second path dependent on the reciprocal of t h e hydrogen ion concentration. The investigations performed a t ionic strength of 1.2 and 2.0 M over a wider acidity range have shown that an additional path dependent on [Hf] also contributes to the complex formation a t higher acidities. Activation parameters for the formation and dissociation of FeS04+ lead one to consider Fe3+ and S042-, rather than FeOH2+ and HS04-, as the reactants in the acid-independent path. The results are in agreement with the view that the elimination of a water molecule coordinated to the metal ion is the ratedetermining step in all cases, even though for the reaction of Fe3+ with Sod2- the water elimination rate may be probably somewhat enhanced.
