550 



Professor Sir James Dewar 



[Jan. 



')•> 



MouREu's Experiments (1913). 



Comparison of Distribution of Rare Gases in Air and in 

 Earth Gases. 



Gases from Thermal Springs 

 and Fire Damp 



Krypton 

 Argon 

 Xenon 

 Argon 

 Xenon 

 Krypton 

 Helium 

 Argon 



divided by 



Krypton 

 Argon 

 Xenon 

 Argon 

 Xenon 

 Krypton 

 Helium 

 Argon 



Ratio 



Roughly constant 



Varies enormously 



The measures of such small quantities of gas, as are here being 

 discussed, will, of course, be liable to errors from many causes, and the 

 conditions of experimenting must therefore be modified in the search 

 for possible variations. For this purpose the application of a high 

 exhaust, such as that obtained by the use of the molecular pump, 

 in conjunction with the cooling methods already described, has 

 yielded some suo-gestive information. 



The manner in which such experiments can be carried out can be 

 seen by referring back to Plate 1. The main stopcock B on the 

 cooling bulb H there shown, besides the connection to the burette, 

 can be turned on to the high exhaust of the molecular pump. By 

 this means both the condensed products in the bulb H and the 

 uncondensable residue in the gauge are subjected to an exhaust of 

 below O'OOOul mm.; which is one-tenth of the unit of pressure 

 employed to express the results ; and approximately one two- 

 thousandth part of the partial pressure in the gauge of the uncon- 

 densable fraction in air. The readings then obtained are shown in 

 the next table : — 



Plate 4. — Occlusion at 20" Abs. of the Uncondensable from Air 

 IN the Condensed Solid Nitrogen and Oxygen. 



Material used 



Air . 



Air nitrogen 



Partial Pressures (in 10* mm.) left from 760 mm. 



181 

 218 



Cooling to 

 20= Abs. 



Exhaust of Eaised to 15° C. ; 



Molecular Pump for Ptecondensed at 

 10 min. at 20= Abs. 20= Abs. 



0-11 



0-075 (1) 

 0-08 (2) 

 0-075 (3) 



0-07 (4) 



(Amounts occluded) 

 4-6 

 1-5 

 0-31 

 0-10 

 0-11 



(1) 

 (2) 

 (3) 



(4) 



