492 PRINCIPLES OF CHEMISTRY 



existing data, notwithstanding their insufficiently definite nature, should 

 find a place even in such an elementary work as the present, all the more as 

 the names of Rayleigh, Ramsay, Crookes and Olszewsky, who have worked 

 upon argon, are among the highest in our science, and their researches among 

 ithe most difficult. 2 These researches, moreover,- "were directed straight to 

 the goal, which was only partly reached owing to the unusual properties of 

 argon itself. 



When it became known (Chapter V., Note 4 bis) that the nitrogen obtained 

 from air (by removing the oxygen, moisture and C0 2 by various reagents) 

 has a greater density than that obtained from the various (oxygen, hydrogen 

 and metallic) compounds of nitrogen, it was a plausible explanation that the 

 latter contained an admixture of hydrogen, or of some other light gas lower- 

 ing the density of the mixture. But such an assumption is refuted not only 

 by the fact that the nitrogen obtained from its various compounds (after 

 purification) has always the same density (although the supposed impurities 

 mixed with it should vary), but also by Rayleigh and Ramsay's experiment 

 of artificially adding hydrogBn to nitrogen, and then passing the mixture over 

 red-hot oxide of copper, when it was found that the nitrogen regained its 

 original density, i.e. that the whole of the hydrogen was removed by this 

 treatment. Therefore ths difference in the density of the two varieties of 

 nitrogen had to be explained by the presence of a heavier gas in admixture 

 with the nitrogen obtained from the atmosphere. This hypothesis was con- 

 firmed by the fact that Rayleigh and Ramsay having obtained purified nitrogen 

 (by removing the 0. 2 , CO., and H 2 0), both from ordinary air and from air 

 which had been previously subjected Jo atmolysis, that is which had been 

 passed through porous tubes (of burnt clay, e.g. pipe-stem), surrounded by a 

 rarefied space, and so deprived of its lighter constituents (chiefly nitrogen), 

 found that the nitrogen from the air which had been subjected to atmolysis 

 was heavier than that obtained from- ah- which had not been so treated. This 

 experiment showed that the nitrogen of ah- contains an admixture of a gas 

 which, being heavier than nitrogen itself, 3 diffuses more slowly than nitrogen 



to subject it to as high a temperature as possible. And the possibility of nitrogen 

 polymerising is all the more admissible from the fact that the aggregation of its atoms 

 in the molecule is not at all unlikely, and that polymerised, nitrogen, judging from many 

 .examples, might be inert if the polymerisation were accompanied by the evolution of 

 neat. In' the following footnotes I frequently return to this hypothesis, not only because 

 I have not yet met any facts definitely contradictory to it, but also because the chief' 

 properties of argon agree with it to a certain extent. 



2 The chief difficulty in investigating argon lies in the fact that its preparation requires 

 the employment of a large quantity of air, which has to be treated with a number of 

 different reagents, whose perfect purity (especially that of magnesium) will always be 

 doubtful, and argon hasjnot yet been transferred to a substance in which it could be easily 

 purified. Perhaps the considerable solubility of argou in water (or in other suitable 

 liquids, which have not apparently yet been tried) may give the means of doing so, and it 

 may be possible, by collecting the air expelled from boiling water, to obtain a richer source 

 of argon than ordinary air. 



. 3 It inight also be supposed that this heavy gas is separated by the copper when the 

 latter absorbs the oxygen of the air; but such a supposition is not only improbable in 

 itself, but does not agree with the fact that nitrogen may be obtained from air by absorb- 

 ing the oxygen by various other substances in solution (for instance, by the lower oxides 



