A Spectrophotometric Study of Trivalent Actinide Complexes in Solution.: I. Uranium

Spectra of uranium (III) were obtained in sulfuric acid and lithium chloride and bromide solutions. Intense hands at 18380 and 18280 cm−1 for concentrated chloride and bromide solutions, respectively, are attributed to 5f‐6d transitions due to the UX2+ species. The stability constant of this complex, or contact‐ion‐pair, has been calculated, β1 = (1.3 ± 0.3)10−3 M−1 for chloride and (1.1 ± 0.2)10−4 M−1 for bromide. These values for the stability constants are much lower than those obtained by other methods for the solvent‐shared‐ion‐pair.