Explosives are substances which, under the influence of heat or shock, or both, are instantly resolved into gases occupying at the high temperature of explosion comparatively enormous volumes, and consequently exert ing tremendous pressure, which disrupts the objective or drives projectiles out of guns. They may be said to consist of bodies such as nitroglycerine and nitrocellulose, which are explosive in themselves, or mixtures of substances which, separately, are or may be nonexplosive, but when intimately mixed are capable of being exploded either by ignition or detonators. Gunpowder is a mechanical mixture of nitre, or Chili nitre, charcoal, and sulphur in proportions of about 75, 15, and 10 respectively, and is still largely employed for blasting purposes, although it has ceased to be used as a military propellant, or nearly so. Its explosive power is due to an enormous evolution of gas from a relatively small quantity of solid substance. The nitre supplies the oxygen necessary for burning up the carbon and the sulphur, at the same time yielding nitrogen gas, It is a socalled “low explosive,” while the “high explosives” have a velocity of explosion some 500 times greater. These high explosives are rich in nitrogen, and when detonated, furnish large quantities of that gas and others which are enormously expanded by the heat generated by the chemical changes which take place, so that they amount to from 10,000 to 15,000 times the volume of the explosive substance itself. Just as nitre supplies the oxygen necessary to burn the charcoal and sulphur contained in gunpowder, so hydrogen is removed from cotton, glycerine, phenol, toluene, etc., and is substituted by groups of the radical NOa, which contain and supply the oxygen essential to the combustion of the associated carbon and hydrogen, the carbon being converted into gaseous oxides and the hydrogen into steam, while at the same time, the nitrogen is also set free in the torm of gas. Some of these substances, and their nitrated forms, may be roughly indicated as follows: Cellulose is chemically changed into nitrocellulose or guncotton ef 2C6H10O5 + 6HNO3 = C12HmO108 + 6HjO. Glycerine becomes changed to nitroglycerine

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Definition of  EXPLOSIVES