278 Lord Rayleigh and Prof. Ramsay. [Jan. 31, 



refused oxidation, and showed no trace of the yellow line of nitrogen, 

 even under favourable conditions. 



When the gas stood for some days over water, the nitrogen line 

 reasserted itself in the spectrum, and many hours' sparking with a 

 little oxygen was required again to get rid of it. Intentional addi- 

 tions of air to gas free from nitrogen showed that about 1 \ per cent, 

 was clearly, and about 3 per cent, was conspicuously, visible. About 

 the same numbers apply to the visibility of nitrogen in oxygen when 

 sparked under these conditions, that is, at atmospheric pressure, and 

 with a jar connected to the secondary terminals. 



IX. Density of Argon prepared by means of Oxygen. 



A first estimate of the density of argon prepared by the oxygen 

 method was founded upon the data already recorded respecting the 

 volume present in air, on the assumption that the accurately known 

 densities of atmospheric and of chemical nitrogen differ on account 

 of the presence of argon in the former, and that during the treat- 

 ment with oxygen nothing is oxidised except nitrogen. Thus, if 



D = density of chemical nitrogen, 



D' = atmospheric nitrogen, 



d = argon, 



a = proportional volume of argon in atmospheric nitrogen, 



the law of mixtures gives 



or d= 



In this formula D' D and a are both small, but they are known 

 with fair accuracy. From the data already given 



65 



079x7925' 



whence if (on an arbitrary scale of reckoning) D = 2'2990, D' = 

 2-3102, we find d = 3'378. Thus if N 2 be 14, or 2 be 16, the density 

 of argon is 20'6. 



A direct determination by weighing is desirable, but hitherto it has 

 not been feasible to collect by this means sufficient to fill the large 

 globe employed for other gases. A mixture of about 400 c.c. of argon 

 with pure oxygen, however, gave the weight 2*7315, 0*1045 in ex- 

 cess of the weight of oxygen, viz., 2'6270. Thus, if a be the ratio 

 of the volume of argon to the whole volume, the number for argon 

 will be 



2-6270 + 0-1045/*, 



