The Richmond Virginian. (Richmond, Va.) 1910-1920, 1915-08-10
ATOMS LOOSELY BOUND
| IN UNSTABLE CONDITION
Major Il. p. O'Hern Gives Scientific
Explanation OF What An Ex-
piosive Is.
DIVIDED IN THREE CLASSES
Effect OF Explosion Dependent Upon
Quantity OF Gas Developed Fer
Unit of Weight and Volume OF the
Explosive.

Washington, ID. C.. Aug. HS
Smithsonian Institution has issued
statement on explosives prepared py
Major Edward p. O'Hern, Of the ORD
nance Department OF the Army:
IAN explosive" says Major OHern,
lis a substance OF which the mole.
cuies are made up of number OF
atoms or units rather loosely bound
together in an unstable condition,
ready to Geek new and simpler COM
binations upon the furnishing OF
sufficient motive force TO start the
operation. This is usually supplied
through a primer ignited by a slow
burning fuse, or by a wire heated by
an electric current.
when started, the heat and shock
developed will cause continuation
Of the action throughout the mass OF
the explosive. The enormous power
that can thus be developed from a
comparatively small quantity OF ma
teriai Is indicated by the thousands
of fragments into which 12-inch
armor-piercing projectile was broken
by the defamation of bursting charge
about 5 IL per cent OF Its weight
Three Glasses.
Major O'Hern divides explosives into
three classes--progressfve or propei-
ling, known as low explosives; deton-
ating or high explosive. and detona-
tors or Eliminates. For all classes
the effect of the explosive IL depend
ent upon the quantity Of gas and heat
developed per unit OF weight and vel
ume OF the explosive. the rapidity OF
the reaction and the character CT the
confinement. If any. given the expfo-
sive charge. The rapidity of reaction
varies greatly with different explosive
substances, and with the manner in
which the explosion Is started.
Black gunpowder. smokeless powder
and black blasting powder are known
as low explosives. for certain of which.
such as smokeless powder. the explo-
sion does not differ in principle from
tsne burning of a piece OF wood or
other combustibles. The combustion
In very rapid. but is surface action
proceeding from layer 10 layer, until
the grain liz consumed. Such materials
are known as low or progressive ex-
plosives, althouh the total power de-
veioped through the combustion OF
unit weight may be very great and
would be destructive unless properly
controlled.
High Explosives.
In high explosives. such as dyna-
blasting powders and most of the
permissible explosives" approved by
the Bureau of Mines for use In mines
where gas explosions are liable to oc-
cur, the progress of the explosive
reaction il not by burning from layer
to layer, but the breaking up of the
initial molecules gives rise to an ex-
plosive wave which Is transmitted
with great velocity in all directions
throughout the mass and causes its
almost instantaneous conversion into
gas The velocity of propagation OF
the decorating wave has been deter
mined for some materials to be mere
than 10000 feet per second, or APP
proximately four miles per second
This form of material IS used in shells
and for bursting purposes
The progressive emission OF gas
from a low explosive. sucsn as burning
gunpowder. produces a pushing eff
feet upon projectiie. whereas the
sudden conversion OF an equal weight
of material into gas. as would happen
with a high explosive such az dyna-
mite or nitroglycerine, would develop
such high pressure and shattering eff
feet az to rupture the gun.
The action of Eliminates Is much
more brusque and powerful man
that of the high explosives. Since
they can be determined by shock or
the application OF heat they are used
in primers and fuses to start action
in both low and high explosives. Ore
of the most important Eliminates is
illuminate of mercury, which produces
pressures Of about $4,000 atmospheres