Pulse radiolysis of oxygen-containing solutions of ferrous perchlorate in perchloric acid (l M) enables the formation and disappearances of a ferric hydroperoxide complex, Fe³⁺HO^–₂, to be observed. The rate constant for its formation by reaction of HO₂ radicals with free ferrous ions is 2.1 ± 0.4 × 10⁶ M^–1s^–1 in the pH range 0–2.1. The complex disappears in a first-order reaction with a rate constant independent of pH in the range 0–2.1. It exhibits a broad absorption in the region 280–600 nm, with ε_{430 nm}= 280 ± 30 M^–1 cm^–1. In the absence of oxygen, a different absorbing species can be seen, attributed to a ferric hydride complex, Fe³⁺H^–. This is formed by the reaction of hydrogen atoms with free ferrous ions with k= 7.5 ± 2 × 10⁶ M^–1 s^–1. It disappears by reaction with hydrogen ions, with k= 1.06 ± 0.1 × 10⁴ M^–1 s^–1. Its absorption spectrum exhibits a maximum at 325 nm, ε₃₂₅= 650 ± 65 M^–1 cm^–1.