The Romance of Modern Chemistry

EXPLOSIONS AND EXPLOSIVES on the slightest provocation; if it is dry, the falling of dust particles, the tread of a fly, or the merest touch with a feather, will be sufficient to make it go off with a bang. The molecules fly to pieces, and a quantity of nitrogen gas and iodine vapour is generated, occupying much more space than the original solid substance. Such a sensitive material is obviously most dangerous to handle, but there are other compounds which exhibit the same character of unstable equilibrium, and which yet can be manipulated safely if due care is taken. As we shall see later, these readily exploded substances fulfil a useful function. One which is extensively employed, and which on that account deserves special notice, is mercury fulminate. This is prepared from mercury, nitric acid, and alcohol, and when pure is a shiny white, crystalline substance con- taining the elements mercury, carbon, oxygen, and nitro- gen. It cannot be kept in a glass-stoppered bottle, for the mere friction between the stopper and the neck would cause it to explode. When struck with a hammer mercury fulminate goes off with a very sharp report, evolving a large quantity of gas—nitrogen, carbon monoxide, and mercury vapour. It is, of course, one of the essential characteristics of an explosive that a small quantity of the substance should yield suddenly a very large volume of gas. In the case of fulminate it is estimated that the gas produced by its explosion would occupy at the ordinary temperature 1300 to 1400 times the bulk of the substance itself. But the actual volume of the gases produced is even much larger than that, for in the explosion of the fulminate a great amount of heat is liberated, in virtue of which the gases are raised to a high temperature, and occupy a much larger space. 167