Redox Reactions of Thallium Clusters in Aqueous Solution

The redox chemistry of thallium clusters in aqueous solution has been investigated by pulse radiolysis and γ‐radiolysis. Using Ru(bpy) 3 2+ as a redox indicator, it is shown that the redox potential of the Tl 4 2+/+ couple is more positive than −1.27 V NHE, and that the Tl + /Tl 2 + couple's redox potential is more negative than −1.27 V NHE. Ru(bpy) 3 + reduces Tl 4 2+ with a second‐order rate constant of 6±2 × 10 8 M −1 s −1 . Metallic particles of thallium are predicted to have a surface plasmon absorption band at 205 nm in water. The reduced Tl content in a sol can be measured by air‐free titration with CCl 4 or methylviologen.