The Romance of Modern Chemistry

CHAPTER XXIX GREAT EFFECTS FROM SMALL CAUSES IT is a commonplace to say that incidents or persons may have an influence quite out of proportion to their apparent value. This is what every one learns sooner or later, but it is worth while noting here how very remarkably this principle is enforced by many facts with which the chemist is familiar. Nature herself, in various striking cases, reminds us that what is apparently insignificant is frequently of the utmost importance. Take the case of carbon dioxide; this gas is present in the atmosphere to the trifling extent of 3 parts in 10,000, and yet it is on this that the whole vegetable life of our globe depends. As was pointed out in a previous chapter, it was not until the existence and significance of this Twths of 1 per cent, of carbon dioxide were appreciated, that the miracle of vegetable growth could be rightly interpreted. Modern chemistry furnishes many remarkable instances of the way in which the history of a chemical change or the behaviour of a particular substance is profoundly modified by the presence of small quantities of foreign material. It is not necessary to go far afield in search of such cases, for water, one of the commonest chemical compounds, has recently been shown to have an extra- ordinary influence in promoting chemical action between other substances. 326