The Romance of Modern Chemistry

GREAT DISCOVERIES suspected. That argon, as this gas is now called, should have so long remained undiscovered, is due to the fact that it is extremely similar to nitrogen; it is, therefore, difficult to find any way of distinguishing and separating the two gases when they are mixed together, as in ordinary air. As a matter of fact, argon is rather heavier, bulk for bulk, than nitrogen, and it was this slight difference which Lord Rayleigh observed and followed up. Suppose the reader tries to realise how very small was the difference in weight actually observed. The globe which Lord Rayleigh used in weighing gases was filled, firstly, with nitrogen—“atmospheric” nitrogen— obtained from air by removal of oxygen, moisture, and carbon dioxide; secondly, with nitrogen prepared from various chemical compounds. Although these two samples would naturally be expected to exhibit the same behaviour, the weight of the “atmospheric” nitrogen filling the globe was one-seventh of a grain heavier than the weight (35| grains) of the “ chemical11 nitrogen filling the same globe. This is obviously quite a small difference, and probably many investigators would have attributed the discrepancy to some error in their experiments, and thought no more about it. Not so Lord Rayleigh; after showing that numerous possible sources of error were excluded, he succeeded, in co-operation with Pro- fessor Ramsay, in separating and examining the argon which is responsible for the greater weight of “atmos- pheric ” nitrogen as compared with “ chemical11 nitrogen. From all this the reader will see what a high value attaches to close and trustworthy observation even of trifling occurrences. Elaborate apparatus and costly materials are all very well, but what is primarily essential 341