J$xr (U.S..4 .) (Rcccivcd Dcccmlxr gth. rgG7) N-Bcnzoyl-N-phenylhydroxylaminc (BPHA), a cupferron analog, is used extensively as an organic precipitant' and solvent extractant since it reacts with sevcral metals to form stable chelates that are soluble in organic solvents. BPHA, however, is superior to cupferron because it exhibits good thermal and chemical stability, and it forms chelates with several metals in concentrated acids. In strong acids, BPHA becomes more selective and reacts only with some transition elements. Conscquently, the solvent extraction from uranium of 52 elements with BPHA-chloroformhydrochloric acid was thoroughly investigated; particular emphasis was devoted to extraction of easily hydrolyzed transition metals. ALIMARIN ANI) PETRUKHINS investigated the extraction of the benzoylphenylhydroxaminates of niobium, tantalum, titanium, vanadium, and zirconium from strong sulfuric acid. NABLVANETSd found that extraction of easily hydrolyzed elements at PH so is often suppressed by formation of polymeric or colloidal particles; therefore, extraction from concentrated acids is desirable. LYLE AND SHENDRIKARG investigatedextraction of antimony and tin from strong hydrochloric acid or perchloric acid with BPHA. RYAN~ extracted vanadium from strong hydrochloric acid with BPHA. During the development of calorimetric procedures for vanadium and titanium in uranium', it was found that the extraction of their BPHA chelates from hydrochloric acid was superior to sulfuric acid. Studies of the extraction characteristics of niobium, tantalum, and zirconium with the BPHA-chloroform-hydrochloric acid systems, therefore, were extended to include a total of 52 elements. From these studies, a method was developed for the quantitative separation of hafnium, niobium, tantalum, titanium, vanadium, and zirconium from uranium. After the elements have been separated, they can be determined by chemical or instrumental methods. ESPERlMENTAL A preliminary survey was made of extraction characteristics of elements in Croups I through VIII, the rare earths, and the actinides with the BPHA-chloroformhydrochloric acid system. Extraction efficiencies of the elements, grouped into 3 categories, are shown in Fig. I. + Prcscnted in part at the Tenth Confcrencc on Analytical