The Romance of Modern Chemistry

EXPLOSIONS AND EXPLOSIVES substances are dissipated by the force of the explosion in a state of fine division, and form the smoke. From such salts the modern high explosives are free, and they are consequently smokeless, or very nearly so. The applications of gunpowder are therefore more restricted than they once were. For firearms, large and small, it has been replaced by smokeless powders, but it is still largely employed for blasting purposes. It enters also into the composition of fireworks, in which, however, potassium chlorate frequently acts as the oxygen-supplying constituent instead of saltpetre. In the manufacture of modern high explosives a new and interesting principle has been introduced. Gun- powder, as we have seen, is an intimate mixture of three solids, two of which are readily combustible, while the third supplies the oxygen necessary for combustion. In order that gunpowder may be a good explosive it is manifestly essential that the mixing of the constituents should be very thorough ; provision must be made, as it were, for each combustible molecule finding near at hand another molecule out of which it can get the necessary oxygen, so that when the powder is fired no time may be lost, and the explosion may be as rapid as possible. As a matter of fact, great pains are taken in the manufacture of gunpowder to secure the most thorough mixing of the constituents. Now in the modern high explosives the oxygen is intro- duced, not in the form of a compound which lies along- side the combustible constituent, but actually in the same molecule. In other words, chemical compounds are used as explosives instead of mechanical mixtures such as gun- powder is. This device secures an almost perfect mixing of the combustible elements with the oxygen, arid the 173