DYNAMITE (from Greek dynamis, power), an explosive invented by Nobel in 1866 and originally consisting of infusorial silica or diatomaceous silica, called alcieselguhr,') and nitroglycerin. The kieselguhr, being composed of the siliceous skeletons of micro-organisms, is a very fine, dry powder with a great capacity for absorbing and holding liquids, and it will absorb and retain three times its own weight of nitroglycerin, so that the product contains 75 per cent by weight of the nitroglycerin, and is known as dynamite No. 1. Other grades are made by adding less nitroglycerin to the absorb ent or dope. The name has now been extended to cover a great variety of pulverulent or plas tic solid mixtures of which nitroglycerin is a mite is fired by means of a detonator or blasting cap. As the percentage of nitroglycerin in dynamites with inert bases is reduced, they become more difficult to detonate until when the nitroglycerin is below 30 per cent they can not, according to Howe, be detonated at all. This does not hold true for dynamites with active bases. Dynamite is usually put up in cylindrical brown paper wrappers, closed at each end and coated with paraffin. These cartridges or °sticks," as they are called, are usually from one to two inches in diameter and eight inches long, and they are packed for transportation in sawdust in wooden cases, there being 50 pounds in each case. The sticks are paraffined to pre vent water reaching the dynamite, as this drives the nitroglycerin out of the kieselguhr dyna mites and dissolves the nitrate of soda in the nitro-lignin dynamites, thereby diminishing their efficiency. Good dynamite is of about the con sistency of fresh mold. It varies greatly in color according to the absorbent used, magnesia pow der being snow white, kieselguhr dynamite No. 1 pearl gray to red, carbo-dynamite black, the lignin dynamites about the color of coarse brown sugar. There is usually a little sodium, calcium, or magnesium carbonate, mixed with the dope. Dynamite keeps as well as the nitroglycerin, from which it is made. It is safer than the lat ter, because it avoids the liquid state, while from its softness it will bear blows better. Its sensitiveness to blows increases very rapidly with the temperature, so that, according to Eissler, °at 350° F., the fall upon it of a dime will explode it." At ordinary temperatures it may be exploded by firing musket balls into the mass. The firing point of dynamite is about 180° C. (356° F.), and at this temperature it either burns or explodes. If free from all pres sure, jar, vibration, or force of any kind, it burns ; otherwise, it explodes. If a thin layer
be placed on a plate of tin and heated over a burner the nitroglycerin volatilizes or takes fire. If the layer is of any considerable depth, say over a quarter of an inch, it explodes. This is a dangerous experiment. When heated to any temperature less than this, it is exploded by a detonator, blow, jar, or vibration with an ease dependent on the temperature and time of ex posure. When ignited in comparatively small quantities dynamite simply burns away fiercely, but with moderate and larger amounts ignition causes explosion. To safely destroy dynamite it should be treated with a solution or emulsion of an alkaline sulphide such as the spent lime from gasworks. High temperatures, much be low the ignition or explosion temperature, cause the nitroglycerin to exude, or in technical terms, °they will make the powder leak," hence a dynamite should be made to resist exudation at the highest temperature to which it may be exposed.
Dynamite freezes at about 40° F., and re mains frozen at temperatures considerably ex ceeding this. If solidly frozen it cannot be detonated except with great difficulty and uncer tainty, but if loose and pulverulent it may be de tonated, though the efficiency is much dimin ished, hence when frozen it is practically useless as a blasting agent, and must be thawed or for use. This operation requires great care and the instructions issued with each case should be closely followed. Many persons suppose that since cartridges of unfrozen dyna mite may sometimes be set on fire and burned without exploding, it is safe to warm it upon a shovel, or in an oven, or to boil it over a stove, or in various other ways which usually lead to a verdict of °accidental death." It cannot be too strongly impressed upon the minds of those handling it that if dynamite or other nitro glycerin preparations are gradually warmed up to a temperature approaching their explosion temperatures they become extremely sensitive to the least shock or blow, and once that point is reached they do not simply ignite, but they ex plode with great violence, and further that, owing to the poor conductivity of the mass, a portion of it may become raised to this tem perature and explode the whole.
Dynamite has a specific gravity of 1.5 to 1.6. In his earlier experiments with absorbents Nobel in 1863 placed gunpowder in a zinc case and filled the interstitial spaces with nitroglycerin. This might be called a dynamite with an active base, but that the nitroglycerin was greatly in excess of that existing in dynamites. See Ex PLOSIVES; NITROGLYCERIN; POWDER.