Contents: Introduction, Studies on the Solvent Extraction of Uranium (VI) with Dibenzoylmethane, Extraction - Spectrophotometric Studies on the U (VI) - DBM - 3, 5, di Br PADAP Mixed Ligand System, Results and Discussion of the Trace Analysis of Uranium, Review of the Earlier Work on the Solvent Extraction and Spectrophotometric Studies on Thorium (IV), Studies on the Solvent Extraction of Thorium (IV) - TOPO - Complex Extracted into Toluene, Spectrophotometric Studies on Th (IV) - TOPO - 3, 5 - di Br PADAP Ternary System, Analytical Applications of Th (IV) - TOPO - 3, 5 - di Br - PADAP Ternary System, Results and Discussion of the Trace Analysis of Thorium.