Method for the Determinations of Niobium and Tantalum in Titanium Alloys and Zirconium-Base Alloys

A method for the anion-exchange separation and gravimetric determination of niobium and tantalum in titanium alloys and zirconium-base alloys has been developed. Niobium up to 40 mg, and tantalum up to 60 mg in 6N hydrofluoric-4N hydrochloric acid solution containing a maximum of 2.5 g of titanium or zirconium ion per 50 mL, can be quantitatively adsorbed on a 35-cm column prepared from 25 mL (swelling volume in water) of the strong-base anion-exchange resin Dowex 1-X4(F, Cl) at the flow rate from 3 to 4 mL per square cm per minute. After washing the column, niobium cotaining no tantalum can be eluted with 200 mL of 3M ammonium chloride-1N hydrofluoric acid solution (A), and tantalum containing no niobium with 200 mL of 3M ammonium chloride-1M ammonium fluoride solution. For a mixture of niobium and tantalum, niobium can be separately eluted with 200 mL of 2.3N hydrofluoric-3.0N hydrochloric acid solution (B). The eluate (A) containing niobium is neutralized with ammonium hydroxide solution. Then niobium, and tantalum in the eluate are precipitated with cupferron at the temperature below 10°C after adjusting the acidity to 1∼2N by the addition of 8 g of boric acid and sufficient hydrochloric acid. Niobium in the eluate (B) is also precipitated quantitatively from 2∼3N hydrochloric acid solution with cupferron after the addition of 40 mL of ammonium hydroxide solution and 15 g of boric acid. The precipitates are filterd, washed, ignited at 1000°C for an hour, and weighed as Nb2O5 and Ta2O5 respectively. Nitric acid may be present up to 3N under the conditions of the adsorption. All elements normally found in titanium alloys and zirconium-base alloys cause no interference under the developed conditions. Amounts of 0.1∼30 percent niobium, and 0.1∼5 percent tantalum in titanium alloys and zirconium-base alloys are determined by a developed method, the results of which show moderate precision and satisfaction.