THEORY OF EXPLOSIONS. An explosion may be defined as a ehemical reaction which is effected in an exceedingly short space of time with the evo lution of a large quantity of gas at a high temperature and accompanied by a .shuck. When this reaction occurs in a body which iS CODilDed, the expansive action of the heated gases pro duces disruptive effects. The force which is de veloped by the passage from the solid form to the gaseous condition depends upon the ingredients of the explosive. When the explosion is pro gressive, that is, starts at an initial point and continues front one group of particles to the next, and so on through the explosive, the action is termed burning and is analogous to ordinary combustion. When, however, the combustion is effected simultaneously throughout the mass in an extremely short space of time, the action is called detonation. The development of an ex plosion may often be explained as resulting from the transformation of a shock into heat. This may be accomplished by the propagation of the shock from particle to particle in an explosive, or by a shock from one explosive body to another not in direct contact. The latter is the syn chronous vibratory theory of Sir Frederick A. Abel, who claims that the originating cause of the detonation of an explosive lies in the syn chronism between the vibrations produced by the body that provokes the detonation and those that the first body would produce in detonation, just as the string of a musical instrument re sounds at a distance in unison with another vibrating cord. Marcellin I'. E. Berthelot, on the other hand, contends that an explosion is due to the transformation of mechanical energy into heat, which, during the explosion, is again trans formed into mechanical energy; that is to say, it is dependent upon the production of two orders of waves, one series of which represents the explosive waves developed in the midst of the matter that detonates, and consists of a con tinually reproduced transformation of the chem ical actions into thermal and mechanical actions which transmit equally the sudden pressure all around the centre of the concussion to the ad joining bodies and thence to a new mass of ex material. Most explosives consist es
sentially of compounds containing carbon, oxygen, and nitrogen, the last of which is in a. state of feeble combination with the whole or part of the oxygen, thus constituting an unstable chemical condition, which is necessary. When the explo sion takes place the nitrogen gives up its oxygen to the carbon, for which it has a greater affinity, forming carbon dioxide and carbon monoxide gases, the combination being attended by great generation of heat, and the nitrogen is set free. In most explosives the carbon is accompanied by hydrogen. which, by its combustion. produces an extremely high temperature and combines with a part of the oxygen to form water in the state of greatly expanded vapor. Other subordinate ele ments are often present: thus, for instance, in gunpowder the potassium holds the nitrogen and oxygen loosely together as saltpetre, and there is sulphur, a second combustible whose oxidation evolves even greater heat than carbon. When potassium chlorate is present the chlorine acts the same as the nitrogen, and is set free in the gas eous state. The foregoing description illustrates those explosives in which the decomposition may be considered a process of oxidation. hut there are cases in which an explosion occurs by the simple dissociation of a compound without oxi dation; thus, nitrogen chloride and nitrogen io dide contain neither carbon nor oxygen, and their great explosive violence is explained by the feeble affinities of nitrogen for other elements.