Azides barium

The salt begins to decompose at 160°C, and once triggered the reaction continues as low as 120°C [103]. When heated above 217°C it deflagrates with a green flash [62]. Barium azide is also sensitive to mechanical shock, exploding with 50% probability on impact of a 10-kg weight dropping from 10 cm [109]. 

All preparation methods for Ba(N3)2 yield first an aqueous solution, from which the salt is precipitated by evaporation or by adding an organic solvent. In either case, mixtures of the monohydric and anhydric forms are obtained, and much confusion about the properties of Ba(N3)2 as reported in the literature [62,74,109,115,126-131] may be attributed to the uncertain composition of the products used. 

Barium azide may be obtained by any of the methods described for calcium azide. When precipitating the aqueous solution, acetone should be preferred as it yields a coarser product [132] which is less likely to contain impurities. The salt has also been synthesized with hydrazine and nitrite 3.5 g barium hydroxide and 200 ml aqueous hydrazine (5% w/w) were cooled with ice and 15 g ethyl nitrite added dropwise with stirring. The next day, excess hydroxide was removed with CO2 the filtrate yielded 8 g barium azide (30% of the theoretical yield) [49]. Small samples of barium azide have also been made according to the Wislicenus process the intermediate amide formed at 260-290°C and the azide at 140-175°C [85], which is, however, already within the range of thermal decomposition. 

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Fig. 15. Isothermal a—time curves for the decomposition of barium azide [696]. (Reproduced, with permission, from Monatshefte fur Chemie.)...

Reduction of the chlorides by Ba, Na or Ca is a satisfactory method of preparing small amounts of pure Rb and Cs. Rubidium chloride is dissolved in barium azide aq sol and evaporated at 25°C to dryness. The intimate mixture is then heated under vacuum. The BafNjIj decomposes at ca. 100-200°C to Ba metal, which reduces RbCI to Rb this distills at temperatures low enough to prevent contamination by Ba vapor. The most widely employed method uses Ca as the reducing agent ... 

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]. 

Calcium, strontium and barium azides are not shock-sensitive, but explode on heating at about 150, 170 and 225 (or 152)°C, respectively. In sealed tubes, the explosion temperatures are higher [1], Although calcium azide is rather mildly endothermic (AH°f (s) +46 kJ/mol, 0.37 kJ/g), it can decompose much more exothermally to the nitride (189.9 kJ/mol, 1.53 kJ/g) than to the elements [2],... 

Ammonium hexacyanoferrate(II), 2577 f Arsine, 0100 Azido-2-butyne, 1473 3-Azidopropyne, 1114 c /.v-A/obcn/cnc, 3484 Azoxybenzene, 3485 Barium azide, 0214 Benzenediazonium nitrate, 2275 Benzotriazole, 2269 Borane, 0135 Bromine azide, 0256 f 3-Bromopropyne, 1090 f 1,2-Butadiene, 1479 f 1,3-Butadiene, 1480 f Buten-3-yne, 1423 f 1-Butyne, 1481 f 2-Butyne, 1482 Cadmium azide, 3957 Cadmium cyanide, 0588 Cadmium fulminate, 0589 Cadmium nitride, 3960... 

Dining the preparation of cellular rubber by thermal decomposition of calcium, strontium or barium azides, various additives were necessary to prevent explosive decomposition of the azide in the blended mixture. 

Barium azide is used in explosives. A saturated solution is generally used. 

Barium azide may be prepared by reacting sodium azide with a soluble barium salt. The solution is concentrated to allow crystals grow. Crystals wdl explode if fully dried, or subject to friction. Product should be stored damp with ethanol. 

Barium azide, dry or wetted with less than 50 per cent water, by mass 0224... 

Barium azide, wetted by not less than 50 % water, by mass 1571... 

According to Jacobs and Tompkins [22] in the reflection spectrum sodium azide and barium azide give a band with the maximum in the vicinity of 240 nyi and 202 m/i respectively. Evans and Yoffe [23] found a value of 248 mfi for potassium... 

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. 

Tompkins et al. [22, 85] studied the photochemical decomposition of potassium and barium azide. Originally they found that the rate of photolysis was proportional to the square of the intensity of the radiation. 

In more recent studies, Jacobs, Tompkins and Young [136] examined the rate of evolution of nitrogen from barium azide as a criterion of the rate of photolysis, and have shown the reaction to be more complex than was previously indicated. A mechanism for the photolysis involving the production and reaction of both exci-tons and positive holes has been formulated. 

According to Ficheroulle and Kovache [137] barium azide has a low sensitiveness to impact (a 2 kg weight falling from 100 cm causes 14% of explosions) but it is very sensitive to friction. It does not possess the properties of a primary explosive,... 

Tompkins [80] investigated the thermal decomposition of silver oxalate at 110— 130°C. Its decomposition, in his opinion, is similar to that of barium azide. 

Cd[C2H4(NH2)2]2 N3)2 mw 325.37, N 26.55% wh ppt, mp - melts deflgr with a bright flame when heated on a Ni spatula readily sol in cold w decomp by dissolving in acids was prepared by reacting Cd triethylene-diamine-sulfate with Barium Azide (Ref 2)... 

AZIDES. The salts of hydrazoic acid are termed azides. Metallic azides can be prepared from barium azide and the metal sulfate, or from potassium azide and the metal perchlorate. 

The azides, except those of mercury) ), Hg(l,i, thalliura(l), 11(1), copper. Cu, silver, Ag, and lead, Pb, are readily prepared from hydrazoic acid and the oxide or carbonate of the metal, or by metathesis of the metal sulfate with barium azide. They are all thermally unstable, giving nitrogen and free metal or occasionally nitride. The azide ion appears to resonate between four structures ... 

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