Assessment of Current Practice

The surveillance study involved analyses of the lead azide and of the media in various regions of the drums, together with paramagnetic resonance and impact-sensitivity measurements on the lead azide. No detectable interaction with the packaging materials or identifiable changes in crystal morphology or size occurred. 

In the case where the use of mbberized cloth bags had been permitted in lieu of polyethylene material, analyses showed the presence of high concentrations of hydrolysis products and products of reaction with the drum in all regions of the drum. Electron paramagnetic resonance measurements showed the presence of iron and manganese in the lead azide lattice, although similar measurements on recently manufactured azide showed only trace amounts of iron and no manganese. The lead azide assay was also low. 

In the cases where polyethylene waterproof bags were used, the lead azide had survived a storage time of approximately six years, although some difference in impact sensitivity and corresponding lead azide content between manufacturers was found and attributed to differences in permeability of the packaging. In each case the azide remained within specifications. 

Notwithstanding the evident ability of commercial products to perform satisfactorily after extended storage, potentially adverse chemical reactions may proceed within the packaging materials. This is discussed in more detail in the following subsection. 

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Jahanmir, S., Ives, L.K., Ruff, A.W., and Peterson, M.B., "Ceramic Machining Assessment of Current Practice and Research Needs in the United States," NIST special publication 834, Gaithersburg, MD, 1992. 

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