Lead styphnate (lead 2,4,6-trinitroresorcinate, C<sub>6</sub>HN<sub>3</sub>O<sub>8</sub>Pb), whose name is derived from styphnic acid, is an explosive used as a component in primer and detonator mixtures for less sensitive secondary explosives. Lead styphnate is only slightly soluble in water and methanol.
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.
:{C<sub>6</sub>N<sub>3</sub>O<sub>8</sub>}MgH<sub>2</sub>O + Pb(CH<sub>3</sub>CO<sub>2</sub>)<sub>2</sub> → {C<sub>6</sub>N<sub>3</sub>O<sub>8</sub>}PbH<sub>2</sub>O + Mg(CH<sub>3</sub>CO<sub>2</sub>)<sub>2</sub>
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<sup>−1</sup>. The loss of water leads to the formation of a sensitive anhydrous material with a density of 2.9 g cm<sup>−3</sup>. 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.
<!-- something messed up here:{C<sub>6</sub>N<sub>3</sub>O<sub>8</sub>}PbH<sub>2</sub>O → Pb(CN)<sub>2</sub> + 4 CO<sub>2</sub> + 1/2 H<sub>2</sub> + H<sub>2</sub>O-->
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.