Silver azide

Structural formula
General
Surname	Silver azide
other names	Bright silver
Molecular formula	AgN 3
External identifiers / databases
CAS number 13863-88-2 EC number 237-606-1 ECHA InfoCard 100.034.173 PubChem 6093372 Wikidata Q418547
properties
Molar mass	149.89 g · mol -1
Physical state	firmly
density	4.98 g cm −3
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 200 P: ?
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Silver azide is the silver salt of hydrazoic acid . It is a highly explosive substance that is used as an initial explosive to detonate explosive charges . It is also known as crack silver , but this common name is ambiguous.

presentation

Silver azide can be made by reacting sodium azide with silver nitrate :

${\displaystyle \mathrm {NaN_{3}+AgNO_{3}\longrightarrow AgN_{3}+NaNO_{3}} }$

properties

Silver azide is in the form of colorless crystal needles. It is extremely explosive, sensitive to shock and heating. Gradually darkening when exposed to light. The softening temperature is 250 ° C, complete melting only takes place at 300 ° C to form a silvery liquid (with decomposition). Rapid heating to 300 ° C causes an explosion. Its crystal structure is rhombic-pseudotetragonal with the space group Ibam (No. 72) (a = 5.6, b = 5.9, c = 6.0 A). The enthalpy of formation is +279.5 kJ / mol.

Silver azide is one of the most effective initial explosives; a charge of 5 mg of loosely layered silver azide is enough to detonate nitropenta loosely filled into a detonator capsule (comparable charges are 15 mg for lead azide with the same experiment , 300 mg for mercury , and 550 mg for lead trinitroresorcinate ) . Silver azide is characterized by the fact that it detonates immediately after ignition (ie without prior deflagration); It is therefore assigned to the so-called lead azide group of initial explosives in the Russian and Czech specialist literature (together with lead azide and silver fulminate; the initial explosives, which change from deflagration to detonation after ignition, such as fiery mercury, lead typhnate or some organic peroxides, are assigned to the so-called fatal mercury group) . Silver azide is characterized by a very small critical diameter of the charge, which can still carry a stable detonation, as well as by a higher resistance to carbon dioxide in a humid environment compared to lead azide; however, like all silver salts, it is sensitive to light. The detonation speed of silver azide charges is 1000-5000 m / s depending on the density and charge geometry. Silver azide, like the other initial explosives of the lead azide group, cannot be “dead pressed” (ie compressed by pressure in such a way that no detonation occurs after ignition). The sensitivity of the silver azide to impact is lower than that of fumed mercury and roughly comparable to that of lead azide; the friction sensitivity depends on the manufacturing method and the crystal size of the product and is roughly comparable to that of lead azide; the sensitivity to electrostatic discharge is higher than that of lead azide; just as the sensitivity to the flame or the “ignition readiness” of the silver azide is higher than that of the lead azide, roughly comparable to that of the fiery mercury.

use

The high price of silver azide stands in the way of broad use as an initial explosive. Its use in small, powerful detonators has been reported. Furthermore, a mixture of 97% mercury and 3% silver azide was used as the initial bang, which combines the advantages of both initial explosives (lower price of mercury and its compatibility with sheet copper sleeves, as well as a stronger initial effect and the possibility of injecting high charge densities without loss of detonation ability due to the addition of silver azide ) united, traded under the trade name "Astryl". However, this application is only of historical interest with the general renunciation of mercury compounds in blasting technology.

safety instructions

Silver azide is a substance that disintegrates explosively and detonates from shock and heat.

Individual evidence

1. ^ Jean D'Ans, Ellen Lax: Pocket book for chemists and physicists . 4., rework. and rev. Edition. Springer, 1998, ISBN 978-3-540-60035-0 .
2. ↑ There is not yet a harmonized classification for this substance . A labeling of Silver azide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), retrieved on May 10, 2018, is reproduced from a self-classification by the distributor .
3. ↑ Patent DE19533487 : Ignition elements and finely graduated ignition charges. Published on March 14, 1996 , inventors: Günther Faber, Helmut Zöllner. ‌
4. ↑ ^{a b} Georg Brauer (Ed.), With the collaboration of Marianne Baudler u a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1002.
5. ^ Robert Matyáš, Jiří Pachman: Primary Explosives . Springer, Heidelberg / New York / Dordrecht / London 2013, ISBN 978-3-642-28435-9 , pp. 19 and 93 .
6. ^ Tadeusz Urbański: Chemistry and Technology of Explosives . 4th edition. tape 3 . Pergamon Press, Oxford / New York / Toronto / Sydney / Paris / Frankfurt 1985, ISBN 0-08-010401-0 , pp. 177 and 182 .
7. ^ Robert Matyáš, Jiří Pachman: Primary Explosives . Springer, Heidelberg / New York / Dordrecht / London 2013, ISBN 978-3-642-28435-9 , pp. 2 .
8. ^ Robert Matyáš, Jiří Pachman: Primary Explosives . Springer, Heidelberg / New York / Dordrecht / London 2013, ISBN 978-3-642-28435-9 , pp. 92-93 .
9. ^ Robert Matyáš, Jiří Pachman: Primary Explosives . Springer, Heidelberg / New York / Dordrecht / London 2013, ISBN 978-3-642-28435-9 , pp. 91-92 .
10. ^ Tadeusz Urbański: Chemistry and Technology of Explosives . tape 4 . Pergamon Press, Oxford / New York / Toronto / Sydney / Paris / Frankfurt 1984, ISBN 0-08-026206-6 , pp. 485-486 .
11. ^ Robert Matyáš, Jiří Pachman: Primary Explosives . Springer, Heidelberg / New York / Dordrecht / London 2013, ISBN 978-3-642-28435-9 , pp. 94 .
12. ↑ Safety guidelines for teaching (RiSU) (PDF; 825 kB) - KMK resolution of March 28, 2003.

Web links

• Experiment: working with silver azide