The Chemistry of Powder and Explosives - Sciencemadness Dot Org

418 PRIMARY EXPLOSIVES, DETONATORS, AND PRIMERS
minimum amounts of fulminate and of the fulminate-chlorate
mixtures which were necessary to detonate several high explosives
in reenforced detonators. It is necessary to specify that the tests
were made with reenforced detonators, for the results would have
been quite different if reenforcing caps had not been used. In
an ordinary detonator TNA required 0.3125 gram of 80/20
fulminate-chlorate instead of the 0.1700 gram which was sufficient
when a reenforced detonator was used.
MINIMUM INITIATING CHARGE
(GRAMS) NECESSARY FOR EXPLOSION
OF 0.4 GRAM OF
PRIMARY EXPLOSIVE TNT TNA Picric Acid
Mercury fulminate 026 0.20 025
90/10 Fulminate-chlorate 0.25 0.17 0.23
80/20 Fulminate-chlorate 024 0.17 022
The reenforced detonators which were used in this work were
made by introducing the weighed charge of high explosive into
the detonator shell and the weighed charge of primary explosive
into the small reenforcing cap while the latter was held in a
cavity in a brass block which served to prevent the explosive
from falling through the hole in the end of the cap. The primary
explosive was then pressed down gently by means of a wooden
rod, the cap was filled by adding a sufficient quantity of the high
explosive from the detonator shell, this was similarly pressed
down, and the reenforcing cap was then removed from the brass
block and inserted carefully in the detonator shell with its perforated
end upward. The detonator was then placed in a press
block, a plunger inserted, and the contents subjected to a pressure
of 200 atmospheres per square inch maintained for 1 minute.
The pressure expanded the reenforcing cap against the detonator
shell and fixed it firmly in place.
The minimum initiating charge was determined as follows.
The amount of sand pulverized by a detonator loaded, say, with
TNT and with fulminate insufficient to explode the TNT was
determined. Another experiment with a slightly larger amount
of fulminate was tried. If this showed substantially the same
amount of sand pulverized, then the charge of fulminate was
increased still further, and so on, until a sudden large increase