Abstract

The detonation of sporting ammunition requires a guaranteed method of igniting a small quantity of percussion sensitive mix contained in a metal chamber known as a cap. This is struck externally by the firing pin. Mercury fulminate, used originally, is highly toxic and unstable. Manufacturers in modern times have therefore based the ignition mixture on the lead salt of trinitro resorcinol (styphnic acid). A typical mixture also contains oxidisers, fuel (to provide a good heat output), and tetrazene as a sensitiser. Percussion caps must fire with absolute reliability when struck by a blow of specified energy content but must not
fire at lower energy inputs. To maintain fine control, tetrazene is used as a relatively weak percussion sensitive explosive in its own right. It is, however, indispensible in the industry as the only sensitiser known for lead styphnate.
Its chemical name is 1-(5-tetrazoly)-4-guanyltetrazene hydrate and it is synthesised from organic salts of amino guanidine. The commercial product with which this paper is concerned is an off white fine powder of low bulk density in short needle crystals of a wide range of sizes. It is stable when submerged in water at ordinary temperatures but is rapidly destroyed by boiling water. The dry powder is a highly sensitive explosive but can be handled safely if sufficiently diluted in inert materials. It is practically insoluble in all common solvents but it can form salts with strong mineral acids. It is decomposed by strong bases such
as sodium hydroxide.

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