Lead styphnate
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Through Water, Static electricity and Lead
Lead styphnate forms six-sided crystals of the monohydrate and small rectangular crystals. Lead styphnate is particularly sensitive to fire and the discharge of static electricity. Long thin crystals are particularly sensitive. Lead styphnate does not react with other metals and is less sensitive to shock and friction than mercury fulminate or lead azide. It is stable in storage, even at elevated temperatures. As with other lead-containing compounds, lead styphnate is toxic owing to heavy metal poisoning.
Preparation
Lead styphnate (or, as it was then called, trinitro-orcinate) was discovered along with many other thrinitroresorcinate salts by British chemist John Stenhouse in 1871, the synthesis route involving action of trinitroresorcinol on lead acetate.
In 1919, Austrian chemist Edmund von Herz first established a preparation of anhydrous normal lead styphnate by the reaction of magnesium styphnate with lead acetate in the presence of nitric acid.
- {C6N3O8}MgH2O + Pb(CH3CO2)2 → {C6N3O8}PbH2O + Mg(CH3CO2)2
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Structure
Normal lead styphnate exists as α and β polymorphs, both being monoclinic crystals. The lead centres are seven-coordinate and are bridged via oxygen bridges. The water molecule is coordinated to the metal and is also hydrogen-bonded to the anion. Many of the Pb-O distances are short, indicating some degree of covalency. The styphnate ions lie in approximately parallel planes linked by Pb atoms.
Properties
Lead styphnate's heat of formation is −835 kJ mol−1. The loss of water leads to the formation of a sensitive anhydrous material with a density of 2.9 g cm−3. The variation of colors remains unexplained. Lead styphnate has a detonation velocity of 5.2 km/s and an explosion temperature of 265–280 °C after five seconds.
Applications
Lead styphnate is mainly used in small arms ammunition for military and commercial applications. It serves as a primary explosive used in firearms primers, which will ignite upon a simple impact. It is similarly used in blank cartridges for powder-actuated nail guns. Lead styphnate is also used as primer in microthrusters for small satellite stationkeeping.