Environ. Sei. Techno/. 1985, 19, 287-287
depend on a rate-limiting step involving a hypothetical bromine-phosphate intermediate. Furthermore, all constants are conceptually defined unlike the value of Kpused by Inman and Johnson which is a “composite” parameter that should be a function of pH if different phosphate species catalyze NHBrz formation in a differential manner according to their mechanism. Registry No. NH2Br, 14519-10-9; NHBr2, 14519-03-0.
Literature Cited (1) Inman, G. W., Jr.; Johnson, J. D. Environ. Sei. Technol. 1984, 18, 219-224. (2) Johannesson, J. K. J. Chem. SOC.1959,2998-3001.
3 to 1 2 (2). On the basis of these results they propose a mechanism similar to Valentine and Jafvert (1). On the basis of the limited pH range we were able to cover due to the experimental limitations imposed by the chemical equilibria, it is not possible to test Valentine and Jafvert’s proposed mechanism below pH 6. Therefore, the calculated values in their Figure 1 are useless below this value. In any case, their alternative mechanism is an appealing proposal. It should also be pointed out we neglected to reference the work by Wajon and Morris (3). They measured the rate of monobromamine formation under conditions similar to ours and found a rate constant of 7.4 X lo7 M-l s-l compared to our value of 4 X lo7 M-l s-l. Registry No. Monobromamine, 14519-10-9; dibromamine,
Richard L. Valentine,* Chad 1.Jafvert Department of Civil Engineering and Environmental Engineering The University of Iowa Iowa City, Iowa 52242
S I R Valentine and Jafvert (1)have correctly noted an error in our eq 23. They have suggested an alternative mechanism with both a specific acid catalysis step and a general acid catalysis by H2P04-which accounts for the pH variation between pH 8.5 and pH 6.0. Unfortunately the experimental limitation preventing the collection of data at lower pH makes it impossible to verify their modified mechanism fully. Recently, Gray et al. have taken data using a pH jump procedure at pH values from
0013-936X/85/09 19-0287$01.50/0
14519-03-0.
Literature Cited Valentine, R. L.; Jafvert, C. T. Environ. Sei. Technol., preceding paper in this issue. Pasquini Christina, S.; Azure, M. T.; Workman, H. J.; Gray, E. T., Jr. “Decomposition of Bromamines in Aqueous Solution: Preliminary Report of the Decomposition Kinetics and Disproportionation of NH,Br”. presented at the 5th Conference on Water Chlorination-Environmental Impact and Health Effect, Williamsburg, VA, June 1984. Wajonl J. E.; Morris, J. C. Inorg. Chem. 1982,21,4258-4261.
Guy W. Inman, Jr., J. Donald Johnson* Department of Environmental Sciences and Engineering The University of North Carolina at Chapel Hill Chapel Hill, North Carolina 27514
0 1985 American Chemical Society
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