Abstract
An investigation of the separation of niobium and tamtalum with organic hydroxanic acids reveals that salicylhydroxamic acid precipitates both elements in the presence of a tartrate from highly acid solutions to solutions with a maximum pH of 6.4. With citrate the pH of the solution can be extended only to 3.0. With oxalate tantalum precipitates under the same pH conditions as with tartrate, but niobium begins to precipitate at pH 4.9. Cinnanyl hydroxamic acid behaves in the same way as the salicyl derivative with the pH of precipitation extended to 6.5 in oxalate solution, 6.5 in tartrate solution, and 2.0 for tantalum and 2.6 for niobium in citrate solution. With phenylarsonic acid tantalum can be precipitated from an ammonium oxalate --sulfuric acid solution, but the complete precipitation of niobium occurs only when the pH is over 4.6. (J.S.R.)
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