Separation of Niobium and Tantalum from Each Other with N-Benzoyl-N-o-tolylhydroxylamine

N-Benzoyl-N-o-tolylhydroxylarnino provides a satisfactory separation, in the cold, of Nb from Ta from a tartrate solution in the pH range of 5.0 to (3.5, even when these are present in the ratio of 1:17 to 21:1. Nb precipitates quantitatively from solutions with acidity ranging from 10% sulphuric acid to a pH of 6.7 and Ta, from 10% sulphuric acid solution to a pH of 1.8. Only Ti and Zr interfere in the determination of Nb at a higher pH 4.5 to 6.0, whereas Ti, Zr, MnO₄^2--, and WO₄^2-- interfere in the determination of both Ta and Nb from a 10% sulphuric acid solution.