The determination of oxygen in refractory metals

It has already been indicated in Chapter VI - Section 3.4, that Schmitt 

They found especially low oxygen concentrations (0.01 to 1 A g/g) in monocrystals of niobium, molybdenum, tantalum, and also in industrial tungsten. 

The efficiency of the equipment described in Chapter II - Section 3.8.3 was evaluated, by irradiating 50 mg of oxide (MoO ) and enclosing half of this quantity in flat molybdenum cylinders (diameter 15 mm, height 2 mm). These synthetic samples, weighing about 2 g, were fused for 3 minutes at 2100°C in the presence of nickel (Ni/Mo = 5). Finally, the activities of the soda asbestos trap and the untreated oxide portion were compared, giving the total yield of the process. The results of these experiments are given in Table VII-19. 

The above fusion conditions were adopted to determine oxygen in molybdenum prepared by sintering under hydrogen. The samples (diameter 15 mm, thickness 1 mm, weight 1.85 to 1.95 g) were irradiated together with the standards 

The irradiation conditions (duration, maximum energy, beam intensity, layout of two alumina standards) and the equipment used to separate 0 are the same as described above. 

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