Precision Spectrometric Determination of Th and Pu in Solutions with Arsenazo III Using Internal Standardization

A spectrophotometric procedure with internal standardization was suggested for precision determination of the concentrations of Th and Pu in the form of colored complexes with arsenazo III in nitric acid solutions. The sensitivity of the method was significantly improved owing to the use of colored complexes. The optical density optimum (0.3-0.5) of the solutions for spectrophotometric measurements can be achieved at concentrations in solution of the element analyzed as low as (2-3) ×10^-6 M, at the arsenazo and HNO₃ concentrations of 1 ×10^-4 and 6 M, respectively. With this composition of the solution, the relative rms deviation of the results for a single run is no greater than 0.15 and 0.3% for thorium and plutonium, respectively.     

Comparative Analysis of the Crystal Field Strengths of Trivalent f Ions in Matrices of Various Symmetries

A comparative analysis of the crystal fields for a number of matrices containing f ions was carried out in terms of the total crystal field strength parameter. A spectrochemical series of systems was constructed, which corresponds to the electronic level splittings for the central ion and shows how the degree of interaction of the f shell with the surrounding varies with the nature of the ligands and outer-sphere cations, as well as with the coordination number, symmetry type, and the metal-ligand interatomic distance.