It has from 2 to 2½ times the strength of gunpowder for equal weights when the charges are well tamped, and 4 times the strength of gunpowder when the charges are untamped; it ignites at a lower temperature than gunpowder, as it may explode at 277° F. and must explode at 400° F.; it is comparatively insensible to shocks—caissons containing dry guncotton have been frequently inflamed by the penetration of a bullet from a military rifle, but never exploded,[11] while wet guncotton in a condition for service cannot possibly be ignited by the same means even at the shortest ranges.
Wet guncotton is not easily ignited, burns up quietly in the open air, is not sensitive to friction; but if fired by a strongly charged percussion-cap it will explode with great violence. It does not deteriorate when wet and is then perfectly safe to handle. It is therefore stored in a wet state (as it cannot be exploded except by the detonation of other disks of dry guncotton); but it should not be exposed to a temperature that will freeze the water in the cakes, if possible. While frost has no effect on dry guncotton, it causes a mechanical disintegration of the wet compressed variety.
In the field the slabs are carried wet; the disks dry and packed in hermetically sealed tins. These disks are used as primers, and have attached to them, when used, a fulminate fuze.
To Fire Guncotton, the fuze is cut to the required length and inserted in the hollow end of the detonator, especial care being taken to push it down so as to rest on the quick-match; the tube is then slightly bent to prevent the fuze from being withdrawn. The small end of the detonator is then gently inserted into the primer (the dry disk) so as to fill the entire length of the hole in the latter. If it is loose, a piece of paper or grass must be wrapped round to make it fit tight. The primer must be placed in close contact with the charge to be fired. Care must be taken that no sparks from the fuze can fall on the charge, which might then burn instead of exploding. Bear in mind that a moist primer is certain to cause failure.
The charge should be in close contact with the object to be demolished.
Transportation.—The handling of high explosives should be done under the immediate supervision of persons thoroughly familiar with the proper methods to be pursued and who will exercise great care and judgment. High explosives should be packed in light wooden boxes properly marked. The French have a wagon containing about 350 lbs. attached to a horse-battery accompanying the cavalry division, acting independently, and two such wagons with the artillery-park. Care is taken that they are not placed too near the other ammunition and are in the safest place under careful observation.
On a steamer place the explosives in a well-ventilated place remote from the engine.
On railways, if the weather be hot, there should be good ventilation and ice in the car, so placed that water cannot reach the explosives.
In winter protect from freezing if possible. Packing in straw or sawdust may be useful. Under no circumstances should cases of fuzes be in the same car, or in the vicinity of the explosive. The packages of guncotton should not be exposed to the sun—cover with paulins, put under shade-trees.
Storage.—At military posts, in ordinary service magazines over which are erected light wooden roofs, so as to insure a draught during hot weather.