Pulse radiolysis of titanium(III) and other metal(III) ions in the presence of formic acid

Abstract

Oxidation of titanium(III) to titanium(IV) by hydroxyl radicals is observed on pulse radiolysis of titanium(III) solutions at pH 1·4 in the absence of formic acid. In the presence of 1·0M-formic acid the formate radical CO₂H (pK_a= 1·4) is produced first, and titanium(III) is subsequently reduced to titanium(II), k=ca. 5 × 10⁶ l mol^–1 s^–1 at room temperature, pH 1·4. Under the same conditions this radical also reduces europium(III), but not ytterbium(III), chromium(III), or scandium(III), Reduction of scandium(III) is not observed at pH 4·2–4·9 in the absence of formic acid.