External gettering has a potential to remove interstitial gaseous impurities from solid niobium (Nb) even below 1500K. The oxygen concentration in the deposit and the Nb bulk is evaluated by a combination of material thermodynamics and mass balance. The removal of oxygen and nitrogen was experimentally studied by using Ti, Y, Zr, Al and Si. Titanium deposited smoothly on the Nb surface in vacuum, and absorbed the gaseous impurities most efficiently. By applying Ti as an external getter on commercial Nb at 1463K, the residual resistivity ratio reached 780. The oxygen distribution was calculated by combining thermodynamics and diffusion data. The experimental deoxidation rate was found to be slower than the calculated value. This may be attributed to the slow growth of the deposited layer, its morphology, and the interdiffused Ti-Nb alloy layer.