The Romance of Modern Chemistry

GREAT DISCOVERIES by heating into its constituent elements, mercury and oxygen. Priestley observed that a gas was given off from the mercury oxide, and when he had collected some of the gas he was able to show that a candle burned in it with a remarkably vigorous flame. To Priestley this was some- thing quite new and fascinating; as he says himself, “ This surprised me more than I can well express; I was utterly at a loss how to account for it.” Further experi- ments showed him that the gas “ possessed all the pro- perties of common air, only in much greater perfection.” He had, in fact, discovered oxygen, and all as the result of curiosity about the jxjwers of his newly acquired lens. He was, it is true, on the look-out for new gases at that time, but, after all, the concentration of the sun’s rays by a lens is a most unusual way of producing heat, and would not naturally be chosen for that purpose. If, however, the investigator’s mind is occupied with a definite subject, it is wonderful how the most trifling occurrences are seen by him to have a bearing on the problem and are made to contribute to its solution. So it was with Priestley, and so it has been in many other cases which might be quoted. One of those which has been put on record occurred in connection with the discovery of blasting gelatine by Nobel. As has been stated in a previous chapter, the dangerously explosive substance nitro-glycerine cannot by itself be safely handled and transported. The difficulty may be got over by soaking up the liquid nitro-glycerine into kieselguhr, and so converting it into the product known as dynamite. It was obvious to Nobel that this operation involved a reduction of the explosive force of 336