154 Liveing and Dewar — Spectrum of the more 



Art. XI L — On the Spectrum of the more Volatile Gases of 

 Atmospheric Air, which are not Condensed at the Tem- 

 perature of Liquid Hydrogen* Preliminary notice by 

 Professor S. D. Liveing, M.A., D.Sc, Professor of Chem- 

 istry University of Cambridge, and Professor Dewar, M. A., 

 LL.D., Fullerian Professor of Chemistry, Royal Institution, 

 London. 



[Read before the Royal Society of London Dec. 13, 1900.] 



In August last some tubes were filled at low pressure by an 

 improved process with the more volatile gases of the atmos- 

 phere. The air was liquefied directly from that above the 

 roof of the Royal Institution by contact at atmospheric pres- 

 sure with the walls of a vessel cooled below —200° C. When 

 about 200 cc of liquid had condensed, communication with the 

 outer air was closed by a stop-cock. Subsequently, communi- 

 cation was opened, through another stop-cock, with a second 

 vessel cooled by immersion in liquid hydrogen, and a part of 

 the liquid from the first vessel, maintained at —210°, was 

 allowed to distil into the second still colder vessel. When 

 about 10 cc had condensed in the solid form in the second ves- 

 sel, communication with the first vessel was cut off, and a 

 manometer showed a pressure t>f gas of about 10 to 15 mm of 

 mercury. 



This mixture of gases was passed into tubes previously 

 exhausted by a mercury pump, but before reaching the tubes 

 it had to pass through a U-tube immersed in liquid hydrogen 

 so as to condense less volatile gases, such as argon, nitrogen, 

 oxygen, or carbonic oxide, which might be carried along by 

 them. Previous trials with tubes filled in the same way, 

 except that the U-tube in liquid hydrogen was omitted, showed 

 that these tubes contained traces of nitrogen, argon, and com- 

 pounds of carbon. The tubes filled with gas which had passed 

 through the U-tube showed on sparking no spectrum of any 

 of these last-mentioned gases, but showed the spectra of hydro- 

 gen, helium, and neon brilliantly, as well as a great many less 

 brilliant rays of unknown origin. In addition, they showed 

 at first the brightest rays of mercury, derived, no doubt, from 

 the mercury pump by which they had been exhausted before 

 the admission of the gases from the liquefied air. After some 

 sparking the mercury rays disappeared, probably in conse- 

 quence of absorption of the mercury by the electrodes, which 

 were of aluminium. 



In one experiment the mixture of gases in the second vessel 

 into which a fraction of the liquefied air was distilled as above 



* From an advance proof received from the authors. 



