Dunnite, also known as Explosive D or systematically as ammonium picrate, is an explosive developed in 1906 by US Army Major Beverly W. Dunn, who later served as chief inspector of the Bureau of Transportation Explosives.[2][3] Ammonium picrate is a salt formed by reacting picric acid and ammonia. It is chemically related to the more stable explosive trinitrotoluene (TNT).
Ammonium picrate was proposed for use as a component in gunpowder by Brugère and Abel as early as 1869: the former proposed to mix 54% of it with 46% of saltpetre while the latter, 60% with 40%.[4] Their compositions gave less smoke and were more energetic than black powder but neither was adopted by any military, even though in the 1890s "semi-smokeless" powder compositions featuring ammonium picrates were sold commercially in the US.[5] It also was a minor component of the Peyton powder made by the California Powder Works which was procured by the US military in the same period.[5]
It was the first explosive used in an aerial bombing operation in military history, performed by Italian pilots in Libya in 1911.[6]It was used extensively by the United States Navy during World War I.[7]
Though Dunnite was generally considered an insensitive substance, by 1911 the United States Army had abandoned its use in favor of other alternatives.[8] The Navy, however, used it in armor-piercing artillery shells and projectiles, and in coastal defense.
By the end of WWI a pound of ammonium picrate cost US government 64 cents, while TNT cost 26.5 c/lb, ammonium nitrate used in amatol only 17.5 c/'b and black powder about 25 c/lb.[9]
Dunnite typically did not detonate on striking heavy armor. Rather, the encasing shell would penetrate the armor, after which the charge would be triggered by a base fuze.
In 2008 caches of discarded Dunnite in remote locations were mistaken for rusty rocks at Cape Porcupine, Newfoundland and Labrador, Canada.[10][11]
Dunnite can be used as a precursor to the highly stable explosive TATB (1,3,5-triamino-2,4,6-trinitrobenzene), by first dehydrating it to form picramide (attaching the ammonia as an amine group instead of an ion) and then further aminating it, using 1,1,1-trimethylhydrazinium iodide (TMHI) made from unsymmetrical dimethylhydrazine rocket fuel and methyl iodide. Thus, surplus materials that would have to be destroyed when no longer needed are converted into a high value explosive.[12][13]