The Chemistry of Powder and Explosives - Sciencemadness Dot Org

356 DYNAMITE AND OTHER HIGH EXPLOSIVES
that they rapidly lose their explosiveness as they lose their liquid
oxygen by evaporation. If they have failed to fire in a bore hole,
the workmen need have no fear of going into the place with a
pick or a drill after an hour or so has elapsed.
Liquid oxygen explosives often explode from flame or from the
s'purt of sparks from a miner's fuse, and frequently need no
detonator, or, putting the matter otherwise, some of them are
themselves satisfactory detonators. Like other detonating explosives,
they may explode from shock. Liquid oxygen explosives
made from carbonized cork and from kieselguhr mixed with
petroleum were used in the blasting of the Simplon tunnel in
1899. The explosive which results when a cartridge of spongy
metallic aluminum absorbs liquid oxygen is of theoretical interest
because its explosion yields no gas; it yields only solid aluminum
oxide and heat, much heat, which causes the extremely rapid
gasification of the excess of liquid oxygen and it is this which
produces the explosive effect. Lampblack is the absorbent most
commonly used in this country.
Liquid oxygen explosives were at first made up from liquid air
more or less self-enriched by standing, the nitrogen (b.p. —195°)
evaporating faster than the oxygen (b.p. —183°), but it was
later shown that much better results followed from the use of
pure liquid oxygen. Rice reports 33 that explosives made from
liquid oxygen and an absorbent of crude oil on kieselguhr mixed
with lampblack or wood pulp and enclosed in a cheesecloth bag
within a corrugated pasteboard insulator were 4 to 12% stronger
than 40% straight nitroglycerin dynamite in the standard Bureau
of Mines test with the ballistic pendulum. They had a velocity
of detonation of about 3000 meters per second. They caused the
ignition of fire damp and produced a flame which lasted for 7.125
milliseconds as compared with 0.342 for an average permissible
explosive (no permissible producing a flame of more than 1 millisecond
duration). The length of the flame was 2% times that of
the flame of the average permissible. In the Trauzl lead block an
explosive made up from a liquid air (i.e., a mixture of liquid
33 George S. Rice, "Development of Liquid Oxygen Explosives during
the War," U. S. Bur. Mines Tech. Paper 243, Washington, 1920, pp. 14-16.
Also, S. P. Howell, J. W. Paul, and J. L. Sherrick, "Progress of Investigations
on Liquid Oxygen Explosives," U. S. Bur. Mines Tech. Paper 294,
Washington, 1923, pp. 33, 35, 51.