The distributions of 57 metallic ions have been measured for three quaternary amines, tetrapropyl, tetrabutyl, and tetrahexyl, into methyl isobutyl ketone from five media, HNOs, H2SO4, HF, HCI, and NaOH, over the concentration range of 0.2 to 5N. Distribution data are presented as plots of per cent extraction vs. normality in a series of 5 periodic charts. Many separations for radiochemical and general analytical application are

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Two spectrophotometric extraction methods specific for uranium are described. Uranium as tetrapropylammoniurn uranyl trinitrate is quantitatively separated from large quantities of diverse ions b y extraction into methyl isobutyl ketone ' (4-methyl-2-pentanone) from an acid-deficienf aluminum nitrate salting solution. Milligram levels are determined by a direct absorbance measurement of the trinitrate complex in the separated organic phase a t 452 mp. Microgram amounts are determined b y adding dibenzoylmethane (1,3-diphenyl-l13propanedione) in an ethyl alcoholpyridine mixture to the separated organic phase and measuring the absorbance of the chelate a t 41 5 mp.The coefficient of variation is less than ly0 a t the IO-mg. and 25-7 levels.The limit of sensitivity is 0.8 y for the dibenzoylmethane method.HIS work was undertaken to de-T velop rapid, reliable, spectrophotometric methods highly specific for the determination of uranium. The trend of specific spectrophotometric methods for metals has been toward selective liquid-liquid extraction followed by direct measurement of the absorbance of the extracted complex for milligram quantities and the addition of a sensitive chromogenic agent to the organic phase (in situ determination) for microgram quantities. Milligram Levels. Several methods for the spectrophotometric determination of milligram levels of uranium are hased on absorbance measurements in acidic media. Silverman and Moudy 122) determined uranium in perchloric acid, Susano, Menis, and Talbott (14) in a sulfate medium, Canning and Dixon ( 2 ) in phosphoric acid, and Smith et aZ. ( I S ) in L-ascorbic acid. All these methods are restricted to essentially pure uranium solutions. Colored ions, especially those of the transition group metals, seriously interfere. A comprehensive discussion of the absorbance spectra of uranyl compounds in solution is given by Rabinowitch (11).I n nitric acid medium, absorbance measurement a t only one wave length is not a satisfactory basis for a n analytical method because the spectrum is a func-tion of nitrate concentration. Multiwave length measurement has been used to determine total uranium (8), but this decreases accuracy and increases analytical time. A series of uranyl nitrate complexes apparently exists, each having a characteristic spectrum (8).Kaplan, Hildcbiandt, and ;\der (' 7) describe a quaternary amine trinitratouranj-l complex that is readily soluble in methyl isobutyl ketone (4-methyl-2-pentanone).A system, based on the extraction of the tetrapropylaminonium trinitrate complex of uranium(T.7) from an aciddeficient aluminum nitrate buffer into this solvent, has been described ( I O ) to separate uranium from diverse ions. The proposed spectrophotometric method is a direct outgroiyth of this n-ork. The method is extremely rapid, involving only an absorbance mcasurement of the separated organic phase at 452 nip. S o other ions extract and absorb a t this wave length. Cerium(1V) and thorium ~i hich are coinplexed by tetrapropylammonium nitrate, thereby using up...