The determination of nitrogen in zirconium and its alloys

The solubility of nitrogen in P-zirconium at 1000°C is 0.8 at.% (1). Contents of a few tens to a few hundreds of / g/g are found in industrial metal and its alloys. Reducing fusion processes and the Kjeldahl method are suitable for their determination. 

Mention should also be made of an oxidizing melt digestion process with lead oxide/sodium metaphosphate or lead oxide/boric acid/sodium metaphosphate, which is stated to digest samples of 0.5 - 1 g, and to liberate the nitrogen contained in them, within about half an hour. The process is carried out under a carbon dioxide stream of 40 - 50 ml/minute (18) and is stated to be suitable for zirconium, but nothing is known about its use in practice. 

In his survey of the state of reducing fusion techniques for the determination of nitrogen in metals, Goward (2) concluded in 1965 that this technique was generally held to be unsuitable for the determination of nitrogen 

Literature contains a variety of denominations for this technique or for more specific variants of it heat (or hot) extraction, reducing (or reductive) fusion, inert gas fusion or vacuum fusion, etc. It was preferred to use the term reducing fusion - in bppos44ioq to oxidizing fusion (Chapter II, section 3.8.2) - as the main characteristics of the method are that the sample is fused under reducing condi-tions (carbon crucible). 

When it is realized that there are also still several unanswered questions relating to the applicability of reducing fusion for the determination of nitrogen in alloy steels (7), the extent of the problems relating to this method of analysing zirconium and its alloys becomes manifest. 

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