The Romance of Modern Chemistry

CHAPTER XV EXPLOSIONS AND EXPLOSIVES THE reader may at some time have seen or handled those curious little things known as “ Prince Rupert’s drops.” These are obtained by allowing drops of molten glass to fall into cold water, where they solidify in a tadpole-like shape. If the tip of the tail of one of these drops is nipped off with the fingers, the whole thing breaks up into dust with a loud explosion. The reason is that the glass which forms the solid drop is in a state of intense strain owing to the very sudden cooling which it has undergone ; the outside and the inside of the drop have cooled at different rates, the particles of the glass are in a state of unstable equilibrium, and the slightest jar upsets the whole structure. There are many chemical compounds which exhibit considerable analogy with Prince Rupert’s drops. The molecules of these compounds have been formed by the combination of a number of atoms, but the equilibrium between the latter is an unstable one, liable to be disturbed by the most trivial exciting cause. An example of this curious behaviour is furnished by nitrogen iodide. This extraordinary substance is prepared by the action of iodine on ammonia, and although generally quite stable in the moist state, it has been known to explode even under water. As usually obtained, it is a chocolate-brown powder which explodes violently 166