The characteristic of H.E. is the extreme violence and suddenness of their detonation.

In order to make them instantly pass from a solid or liquid form to gas, they require a detonator or exploder, which applies a violent shock to them and breaks down the chemical structure of the explosive compound, and enables the flame to pass instantaneously throughout the mass of the compound. This explosive is known as detonation.

The composition of H.E. almost without exception is some organic substance, usually some form of carbon combined with nitrogen. Nitrogen, one of the most inert gases known, owes its explosive value to this very inertness; it combines so very reluctantly that on the least provocation—such as shock—the compound of which it forms a part instantly breaks up into gas, giving the enormous expansion needed for explosive effect.

Ammonal. A gray powder. An Austrian explosive, picric acid plus T.N.T. plus aluminum powder plus nitrate of ammonia plus carbon.

A very safe explosive—will not detonate when struck by rifle bullet, but is very hygroscopic (collects moisture) and when in this condition is liable not to detonate.

Ballistite. Consists of guncotton plus camphor or vaseline. Invented by Nobel in 1888.

Cordite. Consists of nitro-glycerine 55 parts, plus guncotton 37 parts, plus vaseline 5 parts, plus acetone to harden, invented by Sir W. Abel.

Benzol. Or Benzine, used extensively as a motor fuel contains a fair percentage of toluene. (See T.N.T.)

Coal Tar. When subjected to fractional and low-temperature distillation produces many by-products valuable in the making of H.E. These distillations give off “light” and “heavy” oils of coal tar.