IDl.j] on Problems of Hydrogen and the Rare Gases 



5-47 



is therefore so marked on the diagram, and the ordinate at this 

 point can be scaled in parts per million volumes, the unit for this 

 scale being equal to 7'6 x 10~* mm. mercury pressure, which is 

 one millionth of an atmosphere. The rise of pressure is at first 

 linear in both cases, but after the admission of oOO c.c. in the 

 second case the graph begins to bend upwards, and the rate of 

 this bending becomes greater with further increments, showing that 

 the i^artial pressure of those constituents condensed by the charcoal, 

 which up to now had been low, here begins to be appreciable as the 

 concentration in the charcoal increases. The place at which this 

 bending begins depends on the weight of charcoal employed and 

 the mode in which it has been prepared. The two upper graphs, 

 Xos. o and 4, are perfectly linear, which is characteristic of the 



Parts per Million 

 volumes 



200 

 Volume ill c.c. 



Air Nitrogen ' 



condensed at 20^ Ab. (-1) 



Air condensed at 20^ AS. 3) 

 -20— 



: Air in charcoal at 86= Ab. (2; 



-10— 



Air in charcoal at 77- Ab. H] 



355 c.c. (gauge full. 



760 mm. pressure) 



Plate 2. — Proportions of Helium and Hydrogen in Air. 



Comparison of the Use of Charcoal at Liquid Air Temperature with that 



of Liquid Hydrogen. 



results obtained when liquid hydrogen is employed as condensing 

 agent alone. No. 3 deals with ordinary air, and is thus comparable 

 to the charcoal and liquid air results just discussed. No. 4 shows the 

 values obtained when the oxygen is removed from the air, leaving 

 only " air nitrogen." The uncondensable portion is now relatively 

 higher in the same volume, which should be the case if it remains 

 unaffected by the oxygen absorption. 



The difference in the values recorded in No. 3 from those in 

 Nos. 1 and 2 represents the amount of condensation of hydrogen and 

 neon in the charcoal. This is confirmed by its being greater at the 

 lower temperature of boiling nitrogen. No. 1, which lies below No. 2 



