Silver azide explosive properties

Gray and Waddington [57,120] examined the physico-chemical properties of silver azide and state that its melting point is 300°C. On the basis of the latest opinion that the explosive decomposition of azides results from processes involving ions and electrons caused by imperfection and deficiencies in the crystal lattice (Jacobs and Tompkins [22]), the authors incorporated silver cyanide, Ag2(CN)2,... 

The explosive properties of sodium, calcium, strontium and barium azides have been investigated at the Chemisch-Technische Reichsanstalt [135]. These azides differ markedly from lead, silver and cupric azides in that they show none of the properties of primary explosives. All three may be ignited by a spark, a glowing wire or the flame of blackpowder. Calcium azide bums most rapidly and has distinctly marked explosive properties. Larger quantities of it may explode when ignited in a closed tin, while strontium and barium merely bum violently. Calcium azide detonates under the influence of a detonating cap. The sodium azide does not decompose in these conditions. The other azides show weak decomposition under the influence of a standard (No. 3) detonator. Their most important properties are tabulated below. 

The trend in detonator and explosive-train design, which has continued into the 1970s, has been to smaller components, requiring decreased amounts and diameters of more efficient explosives. This trend itself has tended to emphasize the technological importance first of lead and then silver azide and to assure the continued modification of their properties by process development and control. 

The sensitivity of azides to heat is one of their properties which can be most precisely determined. The more practically useful substances, such as lead and silver azides, do not detonate until temperatures close to or at their melting points are attained. Among technologically important sohd explosives such as TNT, tetryl, and RDX, the relatively high melting points of lead and silver azides (<300°C) and the good vacuum stability in standard tests are perhaps not representative of their overall sensitivity. Once a threshold temperature has been attained in the azides, the transition from slow decomposition to detonation is... 

The disorder produced by irradiation has been studied in only a limited number of the explosive azides. The selection of the azides for investigation has undoubtedly been determined by their usefulness for civilian and military applications. Hence silver azide, and, in particular, lead azide, have been studied. Other factors, such as ease of preparation, ease of handling, similarities in properties to azides of practical importance, and purely fundamental considerations have played a roll in the selection of materials. In addition to lead and silver azide only thallium and barium azides have Keen studied to any extent, and this section is devoted almost exclusively to these four materials. All results are for a-Pb(N3)2 unless otherwise stated. 

The discovery of lead azide OLA) is attributed to Curtius who first prepared this substance and characterized its explosive properties in 1891 [2]. In 1893, some experiments with lead, silver, and mercury were carried out in Spandau in Prussia. However, an unexpected explosion occurred during testing of azides with fatal results, which caused termination of further experiments. They were not re-started until 1907 when Wohler drew attention to azides once again as he saw it as a possible substitute for expensive MF [5]. 

All heavy metal azides run very quickly into detonation. This spedlic property has estabhshed the use of silver azide and lead azide as primary explosives in detonators. 

Properties of Ag-salts of 1-(iV-nitramino)-, 2-(Wnitramino)-, 5-(W-nitramino)tetrazole, and l-methyl-5-(fV-nitramino)-tetrazole have been examined. The initiation power of these salts was estimated from minimal blasting charge in RDX. Silver salts of l-(W-nitramino)- and 2-(iV-nitramino)tetrazole have a DDT (deflagration-to-detonation transition) period shorter than the salts of 5-(W-nitramino)tetrazole and l-methyl-5-(W-nitramino)tetrazole. The salt of 2-(fV-nitramino)te-trazole is a more powerful initiative explosive than lead azide <2006MI39>. 

---