ABSTRACT
A century ago, the reduction of silver ions in photographic plates helped W. Roentgen [1], then H. Becquerel [2], to discover x-rays and radiation of radioactive elements, respectively. Various metal ions were subsequently used widely in aqueous solutions as radical scavengers and redox indicators of the short-lived primary radiolytic species, allowing their identification and the calibration of their yield of formation [3-5]. Some underwent reduction by ~_ [6] or pulse radiolysis [7] to the zero-valence metal, to form colloids and then precipitates [7,8].
