Ion-exchange investigation of the arsenazo III-uranyl system: confirmation of the physical existence of a weak M(2)L-type new complex compound

Ion-exchange experiments have proved the physical existence in the arsenazo III uranyl system of an M(2)L complex species in addition to the well-known ML complex. The emerald-green M(2)L complex exhibits a very low stability which permits the preparation of pure stoichiometric bluish ML complex solutions by percolation of the former through a cation-exchanger in the sodium form. Both complexes exhibit a similar visible spectrum with maxima located at 605 and 655 nm, the maximum absorptivity of M(2)L being slightly greater (e(655) approximately 5.8 x 10(4) 1. mole(-1). cm(-1)) than that of ML (E(655) = 5.0 +/- 0.3 x 10(4)). The complexes have a net negative charge which depends strongly on the particular washing conditions used for the complexes sorbed on chloride-form anion-exchange resins.