Silver azide

Lead azide is used as a primary explosive in detonators and fuses to initiate the booster or bursting charge. Generally, it is used in dextrinated form. Lead azide is also used in shells, cartridges, and percussion caps. 

Toxicity data for lead azide are not available. Its aqueous solution is toxic, exhibiting poisoning effect of lead. 

Lead azide is a primary explosive. Its detonation temperature is 350°C (662°F), and the detonation velocity is 5.1 km/s (Meyer 

Its heat of combustion and heat of detonation are 631 and 368 cal/g, respectively (or 184 and 107 kcal/mol). The released gas volume is 308 cm /g at STP. It forms highly shock-sensitive copper and zinc azides when mixed with the solutions of copper and zinc salts. Its contact with these metals or then-alloys over a period of time results in the formation of their azides, too. Reaction with carbon disulfide is violently explosive. There is a report of an explosion resulting from the addition of calcium stearate in a lead azide preparation (MCA 1962). 

The tetrazide salt, unlike the diazide has no commercial use because it is too unstable. 

Silver azide is slightly hygroscopic — at room temperature in a damp atmosphere it picks up approximately 2% of water. 

Silver azide is a very vigorous initiator, almost as efficient as lead azide (cf. Table 32). 

The researches of Wischin [113] and those of Garner and Maggs [84] have shown that metallic nuclei are formed during the slow thermal decomposition of silver azide. These researches were carried out by means of an optical microscope. 

Sawkill [114] recently confirmed this observation using an electron microscope and found that silver is evolved as the result of slow reactions. In the early stage of decomposition intermediate compounds, richer in silver than azide, are formed. The pure metal, which is evolved only in the final stage of decomposition has a markedly oriented structure and a grain size of 0.1 x 0.1 x0.05 mfi. 

Like lead azide, silver azide decomposes under the influence of ultra-violet irradiation. If the intensity of radiation is sufficiently high the crystals may explode (cf. p. 171). 

Silver azide (AgN3) (2.4) is manufactured in the same way as lead azide, by the action of sodium azide on silver nitrate in an aqueous solution. 

Silver azide (SA) was first prepared by Curtius in 1890 by passing azoimide into a silver nitrate solution [1]. 

Of historic interest is a reaction in which the azide group was synthesized from hydrazine and nitrite in the presence of silver ions [19,98] (see p. 24). Most commonly, silver azide is prepared by mixing aqueous solutions of hydraz-oic acid or sodium azide with silver nitrate. The product is precipitated in fine crystalline form larger crystallites are obtained from more dilute reagents [200]. One author recommended the use of an excess of silver nitrate another believed this would enhance the photodecomposition of the product [202]. Of more significance is the recommendation to make the azide in the dark, or at least under red light, [203,204] and to wash the product completely ion free. 

To prepare 3-g batches, a solution of 3.42 g silver nitrate (slight excess) in 100 ml water is placed in a 500-ml beaker and heated to 60-70°C. The solution is stirred with a rubber-clad glass rod, and a solution of 1.3 g sodium azide in 100 ml water (60-70 C) is added within 3-4 min. The precipitate is stirred until well coagulated and then transferred to a Buchner funnel. To avoid contact with the hard funnel material, both the bottom and walls are covered with filter 

The preparation [205] of 45-g batches of silver azide takes place at room temperature in a 4-liter beaker equipped with a stirrer. Silver nitrate, 51.1 g dissolved in 1 liter water, is placed in the beaker and 19.5 g sodium azide, dissolved in 1 liter water, is added with rapid stirring within 45 min. The product is isolated as above. 

Precipitation of silver azide in molten salt media has also been tried by mixing the solutions of silver nitrate and sodium azide in the melt of eutectic NaNOa/KNOa mixtures [206]. 

Of various complexes of silver azide known to exist in solution, [1,196, 200], only the MeL(N3) type has been isolated [164,182] e.g., the compound [P(C6H5)3Ag(N3)] is a white, crystalline solid which melts with decomposition at 170°C. It is made from a suspension of silver azide in benzene, which is treated with triphenylphosphine until soluble. The complex is then precipitated by adding pentane. 

Colour Molecular weight Melting temperature/°C Boiling temperature/°C Density at 20 °C/g cm Enthalpy of formation/kJ mol Energy formation/kJ mol Fine white crystalline solid 149.888 252 297 5.1 +308.78 +312.50 

Silver azide is slightly hygroscopic and is a very vigorous initiator, almost as efficient as lead azide. Like lead azide, silver azide decomposes under the influence of ultra-violet irradiation. If the intensity of radiation is sufficiently high the crystals may explode by photochemical decomposition. The ignition temperature and sensitiveness to impact of silver azide are lower than that of lead azide. Some of its properties are presented in Table 2.5. 

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The azides are salts which resemble the chlorides in solubility behaviour, for example silver azide, AgNj, is insoluble and sodium azide, NaN3, soluble in water. Sodium azide is prepared by passing dinitrogen oxide over molten sodamide ... 

Bromine Ammonia, carbides, dimethylformamide, fluorine, ozone, oleflns, reducing materials including many metals, phosphine, silver azide... 

Iodine Acetaldehyde, acetylene, aluminum, ammonia (aqueous or anhydrous), antimony, bromine pentafluoride, carbides, cesium oxide, chlorine, ethanol, fluorine, formamide, lithium, magnesium, phosphorus, pyridine, silver azide, sulfur trioxide... 

Property Mercury fiihninate Lead azide Silver azide Normal lead styphnate DDNP Tetrazene... 

Silver Azide. Silver a2ide, AgN, is prepared by treating an aqueous solution of silver nitrate with hydrazine (qv) or hydrazoic acid. It is shock-sensitive and decomposes violendy when heated. 

Aluminium triazide Barium diazide Boron triazide Cadmium diazide Calcium diazide Chromyl azide Copper(l) azide Copper(ll) azide Lead(ll) azide Lead(IV) azide Lithium azide Lithium boroazide Mercury(l) azide Mercury(ll) azide Potassium azide Silicon tetraazide Silver azide... 

Chromyl azide chloride Molybdenum azide pentachloride Molybdenum azide tetrachloride Silver azide chloride Tin azide trichloride Titanium azide trichloride Tungsten azide pentabromide Uranium azide pentachloride Vanadium azide dichloride Vanadyl azide tetrachloride... 

Ammonium chlorate Dead azide Silver azide... 

The use of azide reagents is also important for the synthesis of cyclic sulfur(VI)-nitrogen systems. The reaction of SOCI2 with sodium azide in acetonitrile at -35°C provides a convenient preparation of the trimeric sulfanuric chloride [NS(0)C1]3 (Eq. 2.16). " Thionyl azide, SO(N3)2 is generated by the heterogeneous reaction of thionyl chloride vapour with silver azide (Eq. 2.17). This thermally unstable gas was characterized in situ by photoelectron spectroscopy. The phenyl derivative of the six-membered ring [NS(0)Ph]3 can be prepared from lithium azide and PhS(0)Cl. ... 

Various mechanisms involved, as in the decompo sition of silver oxalate or silver azide... 

As a heavy metal azide, it is considerably endothermic (A// +279.5 kJ/mol, 1.86 kJ/g). While pine silver azide explodes at 340°C [1], the presence of impurities may cause explosion at 270° C. It is also impact-sensitive and explosions are usually violent [2], Its use as a detonator has been proposed. Application of an electric field to crystals of the azide will detonate them, at down to — 100°C [3], and it may be initiated by irradiation with electron pulses of nanosecond duration [4], See other catalytic impurity incidents, irradiation decomposition... 

Silver azide, itself a sensitive compound, is converted by ethereal iodine into the less stable and explosive compound, iodine azide. Similarly, contact with nitrogen-diluted bromine vapour gives bromine azide, often causing explosions. 

Pure silver azide explodes at 340°C, but presence of below 10% of copper(I) or (II) oxides or sulfides, copper(I) selenide or bismuth(III) sulfide reduces the detonation temperature to 235°C. Concentrations of 10% of copper(II) oxide, copper(I) selenide or sulfide further reduced it to 200, 190 and 170°C, respectively. 

In a study of dye-sensitised silver azide, it was found that many dyes caused explosions in the initial stages. 

Nitrogen-diluted bromine vapour passed over silver azide or sodium azide formed bromine azide, and often caused explosions. 

Similar in properties to lead or silver azide, it explodes on heating or impact. 

Alone, or Ammonia, or Phosphorus, or Silver azide, or Sodium... 

Use of nitrous acid to liberate a free keto-acid from its semicarbazone caused formation of hydrogen azide which was co-extracted into ether with the product. Addition of silver nitrate to precipitate the silver salt of the acid also precipitated silver azide, which later exploded on scraping from a sintered disc. The possibility of formation of free hydrogen azide from interaction of nitrous acid and hydrazine or hydroxylamine derivatives is stressed. 

See Gold(III) chloride Ammonia Mercury Ammonia Potassium triamidothallate ammoniate Silver azide Ammonia Silver chloride Ammonia Silver nitrate Ammonia Silver(I) oxide Ammonia See N-METAL DERIVATIVES... 

It is less sensitive and a less powerful explosive than silver azide or lead azide. It explodes on heating in air to above 270°C, or after an induction period at 140°C in the dark under vacuum. 

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