Determination of niobium in solution

Separation gravimetric method for determining niobium content consists of the following steps:
(a) Place the sample in a beaker with nitric acid and hydrofluoric acid and heat it until the sample is completely dissolved, then add perchloric acid and heat it continuously until perchloric acid smoke is emitted to remove the silicon contained in the sample;

(b) Adding sodium sulfite and tannic acid to heat and boil to hydrolyze niobium and precipitate separation; After the precipitation is filtered and washed, the filter paper is placed in the original beater, nitric acid and perchloric acid are added to destroy the filter paper, then sulfuric acid is added to heat until smoking, after dissolving the precipitate, sodium sulfite and tannic acid are added again to heat and boil to hydrolyze niobium and precipitate separation, and the mass of niobium pentoxide is weighed after ashing and burning. (c) The mass fraction of niobium is calculated based on the weighing results.