130 Separation of the most Volatile Gases from Air. 



, xh.-msted along with the sparking tube), on opening the stop-cock H 

 uny residuary gas in D was swept into the sparking tube, which was- 

 then sealed off at G. 



This tube gave the hydrogen lines C and F, the neon yellow, and 

 some of the orange lines, along with the helium yellow and green quite 

 distinct. With the residuary gas extracted from 1 litre of air I could 

 see all the helium lines. On the positive pole the neon yellow and the 

 green of helium were alone marked, while the negative pole gave both 

 the neon and helium yellow lines along with the helium green and the 

 F of hydrogen on the continuous spectrum. From this it would appear 

 that the spectroscopic test for helium is as delicate as that for neon, 

 and that l/50,000th can be recognised. From 3 litres of air discharge 

 tubes were obtained giving the neon and helium spectra associated 

 with a brilliant ruddy glow discharge. 



As 40 50 grammes of charcoal can absorb at the temperature of 

 liquid air from 5 6 litres, it is easy to accumulate rapidly the uncon- 

 densed gases in considerable quantities for spectroscopic examination. 

 For this purpose I found it convenient to use two charcoal condensers 

 n circuit as represented in fig. 2. After the charcoal in the first one 

 marked E was saturated, the stop-cock K was closed, while I and J 

 were opened for a short time so as to allow the less condensable gas in 

 E to be sucked into the second vessel of the same type D along with 

 some portion of air. The charcoal condenser E was then taken out of 

 the liquid air, and rapidly heated to 15 C. in order to expel the 

 occluded air. It was thus in a condition to repeat the absorption. In 

 this way 50 litres of air can be treated in a short time. Sparking tubes 

 filled from the accumulated gases in D were very brilliant, showing the 

 complete spectrum of the volatile constituents of air. It is hardly 

 necessary to remark that after the little charcoal receptacle connected 

 to each of the sparking tubes has been cooled and thus all traces of 

 air absorbed, it can be sealed off, leaving the spectroscopic tubes intact, 

 The complete spectroscopic study of the products must be left for 

 further examination with Professor Liveing. 



The method I have described will be equally applicable to the treat- 

 ment of the gaseous products from minerals containing helium, 

 hydrogen, etc., and also to the radium products of a similar kind, 

 . seems even probable that the separation of the less volatile con- 

 stituents in air may be improved by a slight modification in the mode 

 of working. The behaviour of the gases from the Bath Springs has 

 been examined. When the gas containing 1 /1000th part of helium in 

 what may be regarded as pure nitrogen is subjected to charcoal absorp- 

 Jxactly in the same way as the air was treated no high vacuum is 

 All the nitrogen and any other constituents disappear, and 

 i spectrum of helium and hydrogen showing much less neon than exists 

 e volatile residue from atmospheric air is the result. A sample of 



