Standard methods for chemical analysis of reactor and commercial niobium

Photometric methods are described for the determination of N, Mo, W, and Fe in Nb. The limits of the concentration ranges for 15 other impurities in the Nb are specified. N is determined in concentrations from 20 to 1000 ppM by separation as NH3 by steam distillation followed by development of the yellow color with Nessler reagent for measurement at 430 nm. Mo and W are determined in concentrations from 50 to 1000 ppM. The Mo-dithiol complex is extracted with CCl4 from a H2SO4 solution for measurement at 680 nm. W is measured as the dithiol complex at 640 nm in a CCl4 medium after reduction of the W with TiSO4. Concentrations of Fe in the range from 150 to 1000 ppM are measured as the orange-red complex with 1,10-phenanthroline at 508 nm