Alkaline earth azides

Thiatriazole-5-thiol and its salts are readily obtained from the water-soluble alkali or alkaline earth azides with CS2 at 40 °C <64AHC(3)263>. However, these salts should be handled with extreme care as violent explosions have been reported when the alkali salts are spread on a porous plate or rubbed with a spatula. The slightly soluble heavy-metal salts are very sensitive to shock even under water. An improved method for the preparation and storage of sodium thiatriazole-5-thiolate has been reported. The free acid is obtained by addition of concentrated hydrochloric acid to a chilled solution of the sodium salt but can also be prepared from hydrazoic acid and carbon disulfide (Scheme 38). 

The expl props, as detd by Haid et al (Ref 8), indicate that Ca azide is the most powerful of the alkaline earth azides. Although Curtius found that this salt did not expl by percussion, Wohler Martin (Ref 5) and Haid et al (Ref 8) obtained deton by impact (Refs 7 12). When heated rapidly Ca(Nj)3 expl between 144-156°. Heated in a capillary tube, metallic Ca appears at 120-130° (Ref 11) and in vacuo expl between 160-170° (Ref 14). The kinetics of the thermal decompn has been studied by Andreev (Ref 10), Garner Reeves (Ref 19) and others ionic conductance of the solid by Jacobs Tompkins (Ref 18) in the temp range 290-370°K, and initiation and propogation of expln by Bowden Williams (Ref 16) who measured the rate of deton as 770 m/sec. 

Sr(N,)a is not discussed by Sax (Ref 24) but its effects should be considered similar to those of the alkali and alkaline earth azides Sr azide was first prepd in 1898 by Dennis Benedict (Ref 1) and in the same year by Curtius Rissom (Ref 2) by the action of... 

According to Wohler Martin (Ref 6), Zn (N3)a is detonated under impact of a 2 kg wt and exploded in 5 sec at 289°. The heat of detonation is 360 cal/g (Ref 6) and -50.8 kcal/mol (Ref 14). These investigators consider Zn(Ns)a a rather weak expl approaching in its expl props, the alkaline earth azides which are not as powerful as the heavy metal azides... 

Sr(N3)j is not discussed by Sax (Ref 24) but its effects should be considered similar to those of the alkali and alkaline earth azides Sr azide was first prepd in 1898 by Dennis Benedict (Ref 1) and in the same year by Curtius Rissom (Ref 2) by the action of HNj on the oxide, hydroxide or carbonate of Sr. Its prepn has also been described by Mellor (Ref 7), Gmelin (Ref 9), Audrieth (Ref 10) and others (Refs 11, 15, 18, 19 25). The cryst structure of Sr(N3)2 was investigated to a limited extent by A.C.Gill (cited in Ref 1) and in detail by Llewellyn Whitmore (Ref 15) who established its orthorhmb nature as ionic, with a linear sym azide ion, N N 1.12A, and Sr to N distance of 2.63 to 27lX. Kahovec Kohlrausch (Ref 16) detd, from the Raman Effect, both on cryst powd and in soln, frequencies which corresponded to sym. oscillation in a linear triatomic molecule. 

Only the preparation of potassium azide is described here. However, the method outlined below can be adapted to the preparation of the alkali and alkaline earth azides in general. It is also suggested for the purification of technical sodium azide. The usual methods for the synthesis of sodium azide by the nitrous oxide-sodium amide3 method or the hydrazine-alkyl nitrite4 procedure have either not... 

A 3 per cent solution of hydrazoic acid (synthesis 26A) is neutralized with an aqueous solution of pure potassium hydroxide. The resulting solution of potassium azide is concentrated on the steam bath to incipient crystallization. The solution is then made slightly acid with hydrazoic acid to replace the hydrogen azide lost by hydrolysis. A volume of ethyl alcohol twice that of the solution is added, and the solution is cooled in an ice bath. Since the solubility in alcohol of the alkali and alkaline earth azides is very slight (see table below), precipitation in the form of a white microcrystalline salt takes place readily. From 90 to 95 per cent recovery of the theoretical quantity of potassium azide can be effected. The precipitated azide is filtered on a Buchner funnel and washed with cold absolute alcohol and then with ether. Any traces of adhering solvent may be removed in a vacuum desiccator. In a typical run, 300 ml. of a solution of hydrazoic acid containing 8.5 g. of HN3 was neutralized with potassium hydroxide, and the isolation of potassium azide effected as indicated above. Yield 14.7 g. (91.5 per cent) KN3. 

Acetic acid-acetic anhydride, 85 Alkali azides, 79 Alkaline earth azides, 79 Alumino-oxalates, 36 Amalgams, 5 concentration of, 17 preparation of, 6 rare earth metal, 15 Ammonium nitrourethane, 69 Ammonium perrhenate, 177 Antimony oxyiodide, 105 Antimony triiodide, 104 Aquopentammino cobalti bromide, 187, 188... 

Alkali metal azides, 1 79 2 139 Alkali metal cyanates, 2 86 Alkali metal pyrosulfites, 2 162 Alkali metal sulfites, 2 162 Alkaline earth azides, 1 79 Allanite, extraction of, 2 44 Allophanyl azide, formation of, from allophanyl hydrazide, 5 51 Allophanyl hydrazide (1-amino-biuret), 5 48 hydrazones of, 5 51 from methyl and ethyl alloph-anates, 5 50 salts of, 5 51... 

The salts of hydrazoic acid, the azides, have similar properties as the respective chlorides, for example, AgNs, Hg2(N3)2, Pb(N3)2, CuNs, TIN3 have only low solubility in water. The alkali- and alkaline earth azides have ionic structures. With the exception of CsNs (m.p. 483 K), they do not melt without decomposition. Upon heating, they decompose under evolution of dinitrogen. 

Besides alkali halides, alkali and alkaline earth azides have been most thoroughly inveistigated for radiation coloration. By irradiation of freshly precipitated potassium azide at 196°C with radiation of A = 2537 A, Tompkins and Young19 obtained bands due to the presence of F-centres and V-centres. Ageing was found to have marked influence on these bands. The proposed mechanism of ageing involves the formation of anion and cation vacancy pairs... 

A complicating factor observed during the decomposition of the alkaline-earth azides is the reaction between nitrogen and the metal nuclei to produce nitride [11]. The reaction is temperature dependent, and its extent apparently depends upon the size of sample used [12] ... 

An intermediate type of behavior represented by curve b is observed in the alkaline-earth azides Ca [11, 28, 29], Ba [7, 12, 30-32], Sr [28, 30, 33], and cuprous azide [34]. However, the classifications are not rigid, and considerable overlap exists in the literature for the behavior of any one compound. For example, Jach showed that his sample of lead azide exhibited type b behavior until irradiated with neutrons, after which a type a curve resulted [35]. 

Figure 2. Schematic curves for metal azide decomposition. Type (a) behavior is shown by the explosive azides, type (b) by the alkaline earth azides, and type (c) by the alkali azides.

The most detailed consideration of the phenomenon is given by Torkar and Spath [121], who attribute the comparatively low intensity of radiation accompanying the decomposition of the alkaline-earth azides to the formation of nitride species. The reaction scheme involves bimolecular decomposition of N radicals at the reaction interface ... 

Barium azide is the only alkaline-earth azide to have been studied by ESR. Although the cation is heavy and divalent, the compound differs from lead azide... 

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