The Chemistry of Powder and Explosives - Sciencemadness Dot Org

454 PRIMARY EXPLOSIVES, DETONATORS, AND PRIMERS
lar. The first mixture is probably the best. The sulfur which is
contained in the second and third mixtures makes them more
sensitive, but also makes them prone to turn sour after they have
been wet-mixed, and these mixtures ought to be made up with
a small amount of anti-acid (calcium carbonate, trimethylamine,
etc., not mentioned in the table). All the mixtures are wet-mixed
with 5% gum arabic solution, loaded wet, and dried out in situ
to form pellets which do not crumble easily.
In a typical friction primer for an airplane flare, ignition is
secured by pulling a loop of braided wire coated with red phosphorus
and shellac through a pellet, made from potassium chlorate
(14 parts) and charcoal (1.6 parts), hardened with dextrin
(0.3 part).
Percussion Primers
Percussion primers produce fire or flame from the impact of
the trigger or firing pin of a pistol, rifle, or cannon, or of the
inertia-operated device in a fuze which functions when the projectile
starts on its flight (the so-called concussion element, the
primer of which is called a concussion primer) or of that which
functions when the projectile strikes its target (the percussion
element). A typical primer composition consists of a mixture of
mercury fulminate (a primary explosive which produces the first
explosion with heat and flame), antimony sulfide (a combustible
material which maintains the flame for a longer time), and potassium
chlorate (an oxidizing agent which supplies oxygen for the
combustion). Sometimes no single primary explosive substance
is present; the mixture itself is the primary explosive. Sometimes
the compositions contain explosives such as TNT, tetryl, or
PETN, which make them hotter, or ground glass which makes
them more sensitive to percussion. Hot particles of solid (glass
or heavy metal oxide) thrown out by a primer will set fire to
black powder over a considerable distance, but they will fall
onto smokeless powder without igniting it. The primers which
produce the hottest gas are best suited for use with smokeless
powder.
Primer compositions are usually mixed by hand on a glass-top
table by a workman wearing rubber gloves and working alone
in a small building remote from others. They are sometimes
mixed dry, but in this country more commonly wet, with water