I. Kinetics of the Oxidation of Iron (II) by Bromine. II. Complex Ion Formation in the Systems Iron (III), Phosphoric Acid. III. Kinetics of the Oxidation of Ferrocyanide Ion by Bromine

Year: 1953

DOI: 10.7907/PDTJ-FP82

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The kinetics of the oxidation of iron (II) by bromine has been studied spectrophotometrically. At (Br[...]) = 0.50 M, tribromide ion was found to be the reactive bromine species, while evidence for HOBr and Br[subscript 2] reacting with iron (II) was obtained at (Br[...]) [...] 10[superscript -3] M. A mechanism involving Br[...][subscript 2] is suggested, and the observed inhibition by iron (III) eliminates an alternative mechanism involving iron (IV) as an unstable intermediate. The catalytic effect of phosphoric acid was investigated.

The ultraviolet light absorption of iron (III) in phosphoric acid was studied. An attempt was made to determine the nature of the complex that is present. The presence of only one complex could not be verified.

The oxidation of ferrocyanide ion by bromine was found to proceed at a faster pace than the analogous oxidation of iron (II). Both molecular bromine and tribromide ion were found to react with ferrocyanide ion when (Br[...]) = 0.05 M. The reaction appeared to be first order with respect to bromine and ferrocyanide ion at H[superscript +] = 0.93 M, but was found to deviate from a simple second order behaviour when the hydrogen ion concentration was decreased to 0.50 M.