An important event in the development of these explosives was Nobel's invention of dynamite with
an active base, an explosive in which the nitroglycerin was absorbed by a mixture of materials which
were themselves not explosive separately, such as potassium, sodium, or ammonium nitrate mixed with
wood meal, charcoal, rosin, sugar.
The nitroglycerin formed a thin coating upon the particles of the solid materials, and caused them to explode if a fulminate cap was used. The patent suggested a mixture of barium nitrate 70 parts, rosin or charcoal 1O, and nitroglycerin 20, with or without the addition of sulfur, as an example of the invention. Nitroglycerin alone was evidently not enough to prevent the deliquescence of sodium and ammonium nitrate in these mixtures, for a later patent of Nobel claimed the addition of small amounts of paraffin, ozokerite,
stearine, naphthalene, or of any similar substance which is solid at ordinary temperatures and is of a fatty nature, as a coating for the particles to prevent the absorption of moisture by the explosive and the resulting danger from the exudation of nitroglycerin.
Dynamite with an active base is manufactured and used extensively in this country and in Canada and
Mexico. It is known as straight dynamite, or simply as dynamite, presumably because its entire
substance contributes to the energy of its explosion. It is made simply by mixing the explosive oil
with the absorbent materials; the resulting loose, moist-appearing or greasy mass, from which oil
ought not to exude under gentle pressure, is put up in cartridges or cylinders wrapped in paraffined
paper and dipped into melted paraffin wax to seal them against moisture.
The strength of straight nitroglycerin dynamite is expressed by the per cent of nitroglycerin which it contains.
Dyagram of dynamite:
A. Sawdust (or any other type of absorbent material) soaked in nitroglycerin.
B. Protective coating surrounding the explosive material.
C. Blasting cap.
D. Electrical cable connected to the blasting cap.
Guhr Dynamite is not hygroscopic. Liquid water however, brought into contact with it, is absorbed by the kieselguhr and displaces the nitroglycerin which separates in the form of an oily liquid.
The nitroglycerin thus set free in a wet bore hole might easily seep away into a fissure in the rock where it would later be exploded accidentally by a drill or by the blow of a pick. Water does not cause the separation of nitroglycerin from blasting gelatin or gelatin dynamite. It tends to dissolve the soluble salts which are present in straight dynamite and to liberate in the liquid state any nitroglycerin with which they may be coated.
Guhr dynamite, made from 1 part of kieselguhr and 3 parts of nitroglycerin, is not exploded by a blow of wood upon wood, but is exploded by a blow of iron or other metal upon iron. The velocity of detonation of guhr dynamite varies with the density of loading and with the diameter of the charge, but does not reach values equal to the maxima under best conditions for nitroglycerin and blasting gelatin.
Judson powder is a special, low-grade dynamite in which 5 to 15% of nitroglycerin is used as a coating on a granular dope made by mixing ground coal with sodium nitrate and su1fur, warming the materials together until the sulfur is melted, forming into grains which harden on cooling and are screened for size. It is intermediate in power between black powder and ordinary dynamite and is used principally for moving earth and soft rock in railroad work.
Nobel's inventions of blasting gelatin and gelatin dynamite are both covered by the same patent.
Seven or 8% of col1odion cotton dissolved in nitroglycerin converted it to a stiff jelly which was
suitable for use as a powerful high explosive. Solvents, such as acetone, ether-alcohol, and
nitrobenzene, facilitated the incorporation of the two substances in the cold, but Nobel reported
that col1odion cotton dissolved readily in nitroglycerin without additional solvent if the
nitroglycerin was warmed gently on the water bath. A cheaper explosive of less power could be made
by mixing the gelatinized nitroglycerin with black powder or with mixtures composed of an oxidizing
agent, such as a nitrate or chlorate, and a combustible material, such as coal dust, su1fur, sawdust,
sugar, starch, or rosin. A typical gelatin dynamite consists of nitroglycerin 62.5%, col1odion cotton
2.5%, saltpeter 27.0%, and wood meal 8%. A softer jel1y is used for making gelatin dynamite than is
suitable for use by itself as a blasting gelatin, and somewhat less col1odion is used in proportion
to the amount of nitroglycerin. All straight nitroglycerin explosives can be frozen. Straight
dynamite when frozen becomes less sensitive to shock and to initiation, but blasting gelatin becomes
slightly more sensitive.
Blasting gelatin exists as a yellowish, translucent, elastic mass of density about 1.63. Strong pressure does not cause nitroglycerin to exude from it. Its surface is rendered milky by long contact with water, but its explosive strength is unaffected. It is less sensitive to shock, blows, and friction than nitroglycerin, guhr dynamite, and straight dynamite, for its elasticity enables it more readily to absorb the force of a blow, and a thin layer explodes under a hammer more easi1y than a thick one. Blasting gelatin freezes with difficulty. When frozen, it loses its elasticity and flexibility, and becomes a hard, white mass. Blasting gelatin takes fire easily from a flame or from the spark of a fuse. Its combustion is rapid and violent, and is accompanied by a hissing sound. If a large quantity is burning, the combustion is likely to become an explosion, and the same result is likely to follow if even a small quantity of the frozen material is set on fire.
Gelatin dynamite is essentially a straight dynamite in which a gel is used instead of the liquid nitroglycerin or l. f. mixture of nitric esters. It is a plastic mass which can be kneaded and shaped. The gel contains between 2 and 5.4% col1odion cotton, and is not tough and really elastic like blasting gelatin. Correspondingly it is initiated more easily' and has a higher velocity of detonation and better propagation.