• r >2 Relation between Viscosity and Atomic Weight for Gases. 



in the two cases, the variation being necessarily more rapid 

 for the repulsive force. Perhaps from this point of view, we 

 should regard the uncorrected radius as referring more 

 particularly to distances from the centre of the atom at 

 which the values of the attractive force become serious, and 

 the corrected or Sutherland radius as the distance at which 

 the forces of repulsion and attraction balance one another. 



Connexion between the Critical Temperature and 

 Molecular Radius. 



It will now be shown that a simple relation exists between 

 the critical temperatures of these gases and their molecular 

 dimensions. Starting from the equation 



rq = \iin\W\ 



obtained from the kinetic theory ; tj being the viscosity, 

 n the number of molecules per c.c, m the molecular mass, 

 V the root m^an square velocity, and \ the effective mean 

 free path. Hence 



if = l ? i 2 m 2 V 2 X 2 . 



Now, raV 2 is proportional to T, the absolute temperature. 

 Therefore 



^=K.n 2 T\, (1) 



m 



where K is a constant not depending on the particular gas. 

 Further, 



V2/17T5 2 



where s is the effective radius. According to Sutherland, 



o 



="^( 1 +.t) 



where s Q is the real radius. Whence 



Combining with (1) we obtain 



r? T 



(3) 



s °i T/ 



q being a constant. Now the. author, has shown that at the 



