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Dihexyl[(diethylcarbamoyl)methyl]phosphonate (DHDECMP) in diethylbenzene extracts actinides well from 6 M nitric acid solution, but commercially available ~H D~c~p~c o n t a i n s impurities which interfere with stripping the actinides from the organic extract. DHDECMP purified by molecular distillation does not contain these impurities, but the pot residue contains increased concentrations of them. Heating the purified DHDECMP causes the formation of products which interfere with stripping in the same way, suggesting that high temperatures employed in the manufacture of DHDECMP may produce the offending impurities. These impurities can be separated from the heat-decomposed material or the pot residues by dilution with a large volume of hexanes (causing part of the impurities to separate as a second liquid phase) followed by equilibration of the hexane solution with dilute alkali. After the treatment with hexane and dilute alkali, thc DHDECMP is readily recovered and functions well in the actinide extraction process. Dibutyl[(dibutylcarbamoyl)methyl]phosphonate (DBDBCMP) and di(2-ethylhexyl)[(diethylcarbamoyl)methyllphosphonate (DEHDECMP) are purified less effectively by these inethods. Similar separation methods using diethylbenzene or CCl4 as solvent do not remove impurities.as completely as the hexane process. Impurities can also be removed from a benzene solution of the DHDECMP pot residue by passing it through a column packed with silica gel or diethylaminoethyl cellulose. These impurities have been separated into fractions for analytical examination by use of various solvents and by column chromatography. Hexyl hydrogen [ (diethylcarbamoyl).methyl] -phospl~onate has been identified tentat.i.vely as a principal objectionable impurity. DihexyL phosphoric acid and possibly dihexylphosphonate have been identified in other fractions. W. W . Schulz,

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