29i J. Dewar — Separation of Gases from, Air. 



is reached. All the nitrogen and any other constituents dis- 

 appear, and a spectrum of helium and hydrogen, showing much 

 less neon than exists in the volatile residue from atmospheric 

 air, is the result. A sample of argon made from Bath gas gave, 

 when the argon was absorbed in charcoal, a gas residuum giv- 

 ing the helium and neon spectrum, and the same result follows 

 the use of atmospheric argon. In the case, however, of the 

 Bath gas argon the helium spectrum is the stronger, whereas 

 with air argon the neon is the most pronounced. 



In order to further test the method, the crude gases got by 

 heating the mineral fergusonite were examined. During the 

 cooling of the charcoal the nitrogen and hydrogen spectra were 

 marked, but in a short time nothing could be seen but the lines 

 of hydrogen and helium. 



Great interest will attach to the behavior of helium, hydro- 

 gen and the most volatile part of air, when subjected to the 

 action of charcoal cooled to the temperature of liquid hydrogen. 

 The method promises to open up many avenues for future 

 inquiry. 



