On the hydrolysis of iodine in alkaline solution: A radiation chemical study

A reaction set has been constructed that describes the radiolysis of N2O-saturated aqueous solutions of iodide ion. The kinetics and mechanism of the hydrolysis of iodine has been reassessed from conductivity measurements at pH 9.5–11.1 using pulse radiolysis (present work) and previously published data on the yields of I2+I3−, HOI+IO− and IO3− produced by the γ-radiolysis of unbuffered solutions [Buxton, G.V., Sellers, R.M., 1985. Radiation induced redox reactions of iodine species in aqueous solutions J. Chem. Soc., Faraday Trans. I 81, 449–471]. The conductivity data are consistent with a value of k5(I2+OH-)=1×1010dm3mol-1s-1 and with the other hydrolysis parameters having values in the following ranges: k-8(HOI+I-)=(0.3-3)×109dm3mol-1s-1, K5(I2+OH-⇌I2OH-)=5–50dm3mol-1, K8(I2OH-⇌HOI+I-)=8.3–0.83moldm-3, based on K5K8=41.5. The values of K5 obtained here are much smaller than the literature values of ca. 1.6×104 dm3 mol−1 [Lengyel, I., Epstein, I.R., Kustin, K., 1993. Kinetics of iodine hydrolysis. Inorg. Chem. 32, 5880–5882]. The γ-radiolysis results are well described by these hydrolysis parameters.