The Romance of Modern Chemistry

PRODUCTION OF LIGHT AND HEAT our streets with electric light instead of gas, and our railways are being electrified.” That is all quite true, but even then we have not got rid of combustion as the source of nearly all our energy. Except where water- power is available, the introduction of electricity means simply that the combustion has been centralised. In- stead of burning gas at each street lamp, we burn coal or gas at some central furnace, and use up the energy of combustion in driving a dynamo; instead of having a fire on each locomotive we have again a central furnace at the power-station. Hence the production of energy, whatever its form, still depends almost exclusively on the time-honoured process of combustion. Now, although the various things which are burned for the purpose of producing light and heat are outwardly very different—gas, coal, paraffin oil, candles, wood, methylated spirits, petroleum, peat, &c.—the process of combustion is essentially the same in each case. The substances just mentioned are alike in containing carbon and hydrogen, either in the form of the elements them- selves, or in the form of compounds, and the process of combustion is simply the chemical combination of these two elements with the oxygen of the atmosphere. Hence, if we understand what happens in the combustion of a candle, for example, we should be able to give an intelli- gent explanation of what takes place in a paraffin oil lamp or in a coal fire. When the carbon and hydrogen in a candle combine with the oxygen of the atmosphere, the products are our old friends carbon dioxide and water. Carbon dioxide is an invisible gas, as the reader will remember, and the water formed in the flame is given off as an invisible vapour. The candle, therefore, gradually disappears as 107