Abstract
The initial reaction between chlorine(III) and iodide ion has been studied by stopped-flow spectrophotometry at 25 °C and ionic strength 1.3 M (NaC104). At low pH (C1.75) and under conditions where the autocatalytic pathways are suppressed, the rate law is found to be >/2 d([I2] + [I3'])/dz = (k,[H+] + k2[H+]2)[Cl(III)][r]/([H+] + Afa) with k, = 4.6 ± 0.7 M'2 s'1, k2 = 31 ± 1 M'3 s'1, and the dissociation constant of chlorous acid = (3.3 ± 0.5) X 10"3 M. The term second order in [H+] had not been observed in earlier studies at higher pH. It may have important consequences for understanding the complex nonlinear behavior of this reaction.