﻿Kinetic T ' heavy of Adsorption, 61)1 



Now if p r is the partial pressure of S r in the gaseous 

 phase, the rate of impact of molecules of this component is * 



\f 9 p T xp r gm. -molecules per second per sq. cm., 



where m r is the molecular weight of S r ; hence the rate of 

 impact on the surface of area w is w times this quantity , 

 which may he written 



(DfjLrpr gm.-molecules per second. . . . (4) 



For a molecule of S r to condense, H must impinge on a 

 spot where there are a r vacant adjacent points of attachment. 

 The chance that a given molecule will find one point vacant 

 is # , and the chance that it will find a r adjacent vacant 

 points will be a, ' 9 if we neglect the possibility that the 

 molecule may need to impinge in an orientation related to 

 the configuration of the vacant points f. Hence the rate of 

 condensation of molecules of S r is 



(ofjL r p r ar gm.-molecules per second. . . (5) 



For equilibrium, the expression (4) must equal the 

 expression (5), and we get the n equations 



v r X, = a)fi r p r ar r = 1 , 2, . . . n j 



or, from (1) 



which from (2) 



fi r «iN v «»N V T'>* 



Vr L -No ^0 J 



^ =^\}-h- ~-hT" ■ • (6) 



where f is written for 



fJLr co / 1 1 ~ 



(7) 



and X,.' = A^, (8) 



and is therefore the saturation capacity of the surface for S r , 

 supposing it to be completely covered by a monomolecular 

 layer of that component. 



* Jeans, 'Dynamical Theory of Gases,' 1916, p. 133. Langmuir, 

 Phys. Rev. ii. p. 331 (1913). 



• t This possibility could probably be allowed for by multiplying 6fr 

 by a constant depending on a r , which could then be included in £.. 



2 Y2 



, 



