Professors Liveing and Dewar, On the most volatile gases. 107 



On the most volatile gases of the atmosphere. By Professors 

 G. D. Liveing and J. Dewar. 



[Read 18 February 1901.] 



Atmospheric air, at ordinary pressure, was liquefied directly 

 by contact with the walls of a vessel cooled below — 200° C. ; 

 when about 200 cc. of liquid had condensed, communication with 

 the atmosphere was closed, and a fraction of the liquid, still kept 

 at — 210° C., allowed to distil into a second, still colder, vessel 

 immersed in liquid hydrogen. When about 10 cc. had collected 

 in the second vessel, in the solid state, communication between 

 the two vessels was closed, and the gas above the solid in the 

 second vessel was found to have a pressure of 10 to 15 mm. of 

 mercury. Some of this gas was pumped out, and 43 per cent, of 

 it was found to be hydrogen. Also tubes previously exhausted 

 and sparked to remove hydrogen from the electrodes, and then 

 filled with gases from the liquid air, at atmospheric pressure, 

 gave the spectrum of hydrogen very strongly. Calculated as a 

 percentage by volume of the atmosphere, hydrogen is present in 

 very small quantity, nevertheless it forms a sensible percentage, 

 and accords with the supposition that there is an interchange of 

 gases by diffusion between our atmosphere and interplanetary 

 space. 



In other experiments the gas above the solid in the second 

 vessel was allowed to pass through a U-tube cooled in liquid 

 hydrogen into tubes previously exhausted ; and the spectra given 

 by electric discharges through them examined. These spectra 

 are brilliant with the red, orange and yellow rays of helium and 

 neon, but shew besides a vast number of other rays, belonging to 

 substances hitherto unknown, which are most brilliant at the violet 

 end, so that they can be photographed, notwithstanding the 

 opacity of the glass tubes, up to a wave-length 3142. Their 

 brilliance depends on the character of the discharge, and is 

 greatest about the negative pole, and with no leyden-jar in 

 circuit. 



These spectra were searched for the characteristic nebular, 

 coronal, and auroral rays. Tubes filled as above described shew 

 no ray at about the wave-length 5007, the brighter green ray 

 of nebulae, though they give a weak ray near, but not in the 

 exact position of the other green nebular ray, \ 4959, and 

 a strong ray close to the strongest ultra-violet nebular ray \ 3727. 

 A tube which had been filled with gas from the second vessel, 

 without first passing through the U-tube cooled in liquid 



