The determination of oxygen in tungsten

Determination of oxygen in tungsten by reducing fusion is a problem for which, even today, there is still no completely satisfactory solution -at least insofar as the analysis of compact samples is concerned. This fact emerges even from the few papers published on this subject to date. 

It has not been possible to date to clarify the situation in the BCR joint research work, either. The principal reason for this is probably that the oxygen content in compact tungsten is too low to be analyzed by reducing fusion. On the other hand compact samples can have very fine cracks in their surface, resulting from the method of preparation, and these cracks, particularly in conjunction with the etching process, can produce considerable errors. Possibly these two facts may also provide the reason why the literature contains only scanty and mutually contradictory data. 

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The determination of oxygen in tungsten by helium-3 activation is described by Vandecasteele et al. (247) and by Revel and Albert (240). Vandecasteele et al. (247) irradiated for 20 min with a 1.5 mA beam of 20 MeV helium-3. The sample was chemically etched in a 1/1 mixture of hydrofluoric and nitric acids, rinsed and dried. The energy corresponding to the etched depth was 13.5 - 14.2 MeV. The sample was dissolved in a mixture of 10 g of sodium hydroxide, 400 mg of sodium fluoride and 2.5 g of sodium nitrate in a nickel crucible. The melt was dissolved in nitric acid and F was... 

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