The Romance of Modern Chemistry

PRODUCTION OF LIGHT AND HEAT it burns, leaving little or no trace behind. To the super- ficial observer the fact that the candle disappears and leaves nothing tangible in exchange might seem to throw doubt on the law of conservation of matter, according to which matter cannot be destroyed. But it will be admitted that the law would still be fulfilled if the dis- appearance of so much matter in one form were com- pensated by the production of an equivalent amount in another form ; and the reader who has followed the argu- ment of the foregoing chapters will recognise that some forms of matter are invisible. The fact is, the invisible products of the combustion of a candle—that is, the carbon dioxide and the water vapour —weigh more than the candle. This is only natural, for just as it takes two to make a quarrel, so there are two parties to a combustion, namely, the combustible substance, in this case the candle, and the supporter of combustion, the oxygen from the air. As the combustion consists in a combination of the carbon and hydrogen of the candle with the oxygen of the air, the products are necessarily heavier than either the candle or the oxygen separately. The chemist can easily show that this is so by absorbing and weighing the carbon dioxide and water, but it will be sufficient for our purpose to show that each of these substances is present in the gases arising from a candle flame. In order to show that carbon dioxide is one product of a candle flame, we may fix a small piece of candle on a wire, light the candle, and lower it into a glass jar, into which we have previously poured a little lime water. When the candle has been allowed to bum in the jar for ten or fifteen seconds, it is taken out, the jar is closed by a cork, and the contents are shaken. It will then be 108