on the Physical Properties of Gases. 



413 



experiments have been made is also some multiple of O . 

 Moreover a slight difference in the values of O for the differ- 

 ent gases would give a greater difference in the law of pressure 

 as the temperature increases. If, on the other hand, O be 

 great, so that ordinary temperatures are < i^o? then as we 

 have seen before, the variation and dissociation is small, and 

 the more so as the maximum range of the Centigrade tempe- 

 ratures would all be small fractional parts of O . Here also 

 variations of O would not produce much difference be- 

 tween different gases at ordinary temperatures. We should 

 be led therefore to suppose that O is in general large. This 

 is also supported by the fact that it is highly probable that at 

 ordinary temperatures the dissociation of the permanent gases 

 is small. For the sake of illustrating this and also to obtain 

 some idea of the magnitude of the variations involved, we will 

 consider more fully the case of two gases, in one of which 

 # = 100°, and in the other =5000°, the degrees being Centi- 

 grade and measured from absolute zero, i. e. —273° C. 



17. In Tables I. and II. below, column 1 gives the tempe- 

 rature ; column 2 the dissociation at the given temperature, 

 the dissociation being measured by the proportion of free 

 atoms to moving particles in the gas ; column 3 gives the 

 value of 1 + f in the formula p = Kp(l + '06, and which we 

 may call the expansibility ; whilst column 4 gives the ratio 



£ 



— (Po> @o being the pressure and temperature at 27° C). 



Po 



Table I. (0 O = 



= -173° C). 









P 



0. 



2y 



x+2y 



i+?. 



Po 













-273 







1 





-173 



•610 



1439, 



0-873 



- 73 



•728 



1-571 



0-953 



27 



•785 



1-647| 



1 



127 



•820 



1-695 



1-029 



227 



•845 



1-732 



1051 



527 



•858 



1-752 



1-063 



00 



1 



2 



1-21 



