Sodium Azide Explosive Properties

The material is impact-sensitive when dry and is supplied and stored damp with ethanol. It is used as a saturated solution and it is important to prevent total evaporation, or the slow growth of large crystals which may become dried and shock-sensitive. Lead drains must not be used, to avoid formation of the detonator, lead azide. Exposure to acid conditions may generate explosive hydrazoic acid [1], It has been stated that barium azide is relatively insensitive to impact but highly sensitive to friction [2], Strontium, and particularly calcium azides show much more marked explosive properties than barium azide. The explosive properties appear to be closely associated with the method of formation of the azide [3], Factors which affect the sensitivity of the azide include surface area, solvent used and ageing. Presence of barium metal, sodium or iron ions as impurities increases the sensitivity [4], Though not an endothermic compound (AH°f —22.17 kJ/mol, 0.1 kj/g), it may thermally decompose to barium nitride, rather than to the elements, when a considerable exotherm is produced (98.74 kJ/mol, 0.45 kJ/g of azide) [5]. 

Many energetic componnds have been reported where the azido group is in conjunction with another explosophore . This has been a popular approach to new energetic materials. 2-Azidoethyl nitrate, an explosive resembling nitroglycerine (NG) in its properties, was synthesized some time ago from the reaction of 2-chloroethanol with sodium azide followed by G-nitration of the product, 2-azidoethanol, with nitric acid. °... 

Gilbert and Voreck synthesized hexakis(azidomethyl)benzene (HAB) (45) from the reaction of hexakis(bromomethyl)benzene (44) with sodium azide in DMF. This azide has been comprehensively characterized for physical, thermochemical and explosive properties and stability. HAB is a thermally and hydrolytically stable solid and not highly sensitive to shock, friction or electrostatic charge but is sensitive to some types of impact. It shows preliminary... 

Sodium azide is a toxic as well as an explosive substance (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd e(j New York John Wdey Sons). Although inert to shock, violent decomposition can occur when heated at 275°C. Contact of solid or solution with lead and copper must be avoided. Reactions with halogens, carbon disulfide, or chromyl chloride can be explosive. Dissolution in water produces toxic vapors of hydrazoic acid. The salt is an acute poison causing headache, hypotension, hypothermia, and convulsion. 

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. 

Trinitrotriazidobenzene (IX) is the only representative of organic azides possessing properties of primary explosives which has some prospect of practical use. Turek [159] prepared it by the action of sodium azide on sym-trichlorotrinitrobenzene (Vol. I. p. 469) and on the basis of its properties which he himself determined he suggested its use as an initiator. 

While the environmental impact of cadmium azide in deep oil deposits is relatively low, the long-term use of Pb(N3)2 and lead styphnate in military training grounds has resulted in considerable lead contamination (see Ch. 1.2.3, see Fig. 1.17). On demand lead azide (ODLA) is available from the reaction of lead acetate and sodium azide. The recently introduced iron and copper complexes of the type [Cat]2 [Mn(NT)4(H20)2] ([Cat]+ = NH4, Na+ M = Fe, Cu NT = 5-nitrotetra-zolate) as green primary explosives [3] are relatively easily obtained and show similar initiator properties as those of lead azide (Tab. 2.2). 

Preparation in solution.1 Hydrochloric acid (30%. 25 ml.) followed by bromine (8.0 g.) is added to an ice-cooled and well stirred mixture of 32.5 g. of sodium azide and 100 ml. of methylene chloride. After 30-60 min. the organic layer containing bromine azide is decanted and used as such. Although the reagent has been reported to have explosive properties.2 no explosions have been experienced in use of the above procedure. 

In the hexaazidostannate(IV), [Sn(N3)6] , the first IVA azido complex appears. In spite of six azido groups, the complex is not very sensitive. The sodium salt deflagrates when shocked thermally but is stable to impact [275] its salts with large organic cations are stable to both stimuli [158,222,228]. There are also known two mixed tin azides, ClSn(N3) [132] and Cl2Sn(N3)2 [271], which are white, hydrolysis-sensitive soHds with explosive properties. 

These compounds, obtainable from the respective chlorides and lithium or sodium azides, have covalent phosphorus-to-nitrogen bonds. Properties are summarized in Table XV. Triphosphonitrilic hexaazide is a colorless, explosive oil... 

Bromine azide is an orange liquid of equally treacherous properties. Spencer made the compound in 1925 [337] from bromine/nitrogen mixtures and dry sodium azide (BrNa hydrolyzes instantly in water) and noted its pungent but sickly smell and its extreme sensitivity to mechanical and thermal shock. A third of his attempts to establish the melting point (-45°C) ended with explosion, reducing the apparatus to powder. The compound is, even at reduced pressure, highly sensitive to pressure fluctuations Dehnicke [10] found a pressure of 0.05 mm Hg sufficient to cause an explosion. Hassner and Boerwinkle [341] have used BrNa in situ in dichloromethane/pentane media at 0°C for stereospecific syntheses. Solutions of the compound in organic solvents are photosensitive and decompose within hours. 

The decreasiug pattern above is of little practical iuterest, however, as all the heavy metal azides detouate violeutly upou heatiug aud mechauical impact. Table 33.1 lists the heat of formatiou AHf(s) for some azides. It may be seeu that explosivity decreases with a decrease of AH° and at a low value of +16.8 kcal/mol, sodium azide is nonexplosive. Discussed below are individual compounds of commercial interest or those presenting severe explosion hazard. The explosive properties of additional compounds are highlighted in Table 33.2. 

Alkaline fulminates—sodium and potassium—are soluble in methanol, not soluble in acetone and ethanol, and insoluble in ether and benzene [39, 107]. Sodium fulminate explosively decomposes by action of sulfuric acid in the same way as MF and SF do [15]. The spontaneous explosion is reported even during drying above sulfuric acid [108]. The density of alkali fulminates is similar to alkali azides sodium fulminate 1.92 g cm and potassium fulminate 1.80 g cm [39]. Sodium fulminate forms an anhydride or monohydrate depending on preparation procedure. Alkaline fulminates can be stored for a long time in the form of methanol solutions in the dark. These fulminates are hygroscopic they are not stable in contact with moisture and quickly decompose when wet (white color changes to yellow and brown with loss of explosive properties) [15, 107]. Toxicity of sodium fulminate is about the same as that of sodium cyanide [2]. 

As opposed to alkaline azides which do not have properties of explosives, alkaline fulminates are mostly reported as highly sensitive and explosive substances [8,107, 108] even though one source mentioned sodium fulminate as not so sensitive (impact sensitivity for NaCNO to be 32 cm with 0.5 kg hammer compared to 7.5-10 cm MF under the same conditions) [27]. Sensitivity of these fulminates is reported as extreme and handling a hazardous operation [8, 107, 108]. Extreme sensitivity is further reported for the rubidium and cesium salts. Alkaline fulminates undergo explosion when initiated by flame, even in small amounts, whereas mercury fulminate only deflagrates. The exact sensitivity data are, however, not reported in this work [107]. Sensitivity of cadmium fulminate to impact is about the same as that of MF sensitivity of thallium fulminate is higher [15, 57]. 

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