Photometric determination of niobium by the formation of niobium-- molybdenum blue

The formation of a blue niobium- molybdenum heteropolycomplex in the interaction of niobium with molybdenum(VI) and molybdenum(V) was studied. Complexes of different composition (Mo(VI):Mo(V) = 5:1, 7:1, and 11:1) are formed in the NbMo(VI)-Mo(V) system at niobium concentration of between 2 x 10/sup -6/ and 1 x 10/sup -5/-M. A photometric method was developed for determining niobium in heat-resistant alloys with the sensitivity of 0.01%. The mean error is 3%. (auth)