254 PHENOMENA DEPENDENT ON MOLECULAR PATHS 95 



in the negative direction i.e. towards the origin of the tube 

 more than in the opposite direction. 



There are, similarly, more particles of the second kind 

 which cross the same surface in the same time, but in the 

 positive direction from the beginning of the tube, than in 

 the opposite direction, and the number representing this 

 excess is 



where A 2 has a meaning corresponding to that of A r 



Through this double flow the number of particles on 

 the side of the section towards the origin increases by 



- A0), 



and thus an inequality of pressure arises which at once 

 disappears again by causing 



particles of the mixture, and thus 



N and 



particles of the two kinds respectively to cross the section 

 towards the end of the tube. 1 



The number of particles, therefore, of the first kind 

 which finally diffuse in unit time over unit area towards the 

 origin of the tube is 



The oppositely directed diffusion of the second gas has the 

 same strength, for it is 



From this number of the particles which cross unit area 

 in unit time we obtain the change of the partial pressure of 

 each of the two gases which is due to them directly expressed 

 by the formula 



+ 



1 Gross contests, wrongly, as I think, the correctness of this conclusion. 

 Wied. Ann. 1890, xl. p. 424. 



