526 Lord Bayleigh [April 5, 



The difference is about 11 milligrams, or about one-balf percent. ; 

 and it was sufficient to prove conclusively that the two kinds of 

 nitrogen — the chemically-derived nitrogen and the atmospheric 

 nitrogen — differed in weight, and therefore, of course, in quality, tor 

 some reason hitherto unknown. 



I need not spend time in explaining the various precautions that 

 were necessary in order to establish surely that conclusion. One had 

 to be on one's guard against impurities, especially against the 

 presence of hydrogen, which might seriously lighten any gas in 

 which it was contained. I believe, however, that the precautions 

 taken were sufficient to exclude all questions of that sort, and the 

 result, which I published about this time last year, stood sharply out, 

 that the nitrogen obtained from chemical sources was different from 

 the nitrogen obtained from the air. 



Well, that difference, admitting it to be established, was sufficient 

 to show that some hitherto unknown gas is involved in the matter. It 

 might be that the new gas was dissociated nitrogen, contained in that 

 which was too light, the chemical nitrogen — and at first that was the 

 explanation to which I leaned ; but certain experiments went a long 

 way to discourage such a supposition. In the first place, chemical 

 evidence — and in this matter I am greatly dependent upon the kind- 

 ness of chemical friends — tends to show that, even if ordinary nitrogen 

 could be dissociated at all into its component atoms, such atoms 

 would not be likely to enjoy any very long continued existence. 

 Even ozone goes slowly back to the more normal state of oxygen ; 

 and it was thought that dissociated nitrogen would have even a greater 

 tendency to revert to the normal condition. The experiment sug- 

 gested by that remark was as follows : to keep chemical nitrogen — 

 the too light nitrogen which might be supposed to contain dissociated 

 molecules — for a good while, and to examine whether it changed in 

 density. Of course it would be useless to shut up gas in a globe and 

 weigh it, and then, after an interval, to weigh it again, for there 

 would be no opportunity for any change of weight to occur, even 

 although the gas within the globe had undergone some chemical 

 alteration. It is necessary to re-establish the standard conditions of 

 temperature and pressure which are always understood when we speak 

 of filling a globe with gas, for I need hardly say that filling a globe 

 with gas is but a figure of speech. Everything depends upon the 

 temperature and pressure at which you work. However, that obvious 

 point being borne in mind, it was proved by experiment that the gas 

 did not change in weight by standing for eight months — a result 

 tending to show that the abnormal lightness was not the consequence 

 of dissociation. 



Further experiments were tried upon the action of the silent 

 electric discharge — both upon the atmospheric nitrogen and upon the 

 chemically-derived nitrogen — but neither of them seemed to be 

 sensibly affected by such treatment ; so that, altogether, the balance 

 of evidence seemed to incline against the hypothesis of abnormal 





