on Osmotic Theory. 213 



iTfo for the solution, and ir b and ir hn for the pure gas, 

 we get 



i s b dp=\ ^dp (8) 



Fig. 4. 



bp 



wmmzm 



Pure gas 

 B. 



(1) 



B dissolved 

 iD A. 



(2) 



L 



Under the conditions already discussed (p. 272) the left 

 hand of (8) approximates to the form — k's b \og (1 — a), and 

 this imposes a restriction on the form of the characteristic 

 equation of a gas. 



Stratification and Diffusion in Mixed Vapours or Gases. — 

 In the relation (1) , if we change the limits * ttJ to 



ty — Ti a + dp — ^^*dp, 7r a to yfr — TI a , and yfr' to ^ + dp, 

 Op 

 we get 



\ Jad 





p 



ft\p+dp 



\ <Ta d P> 



J -J, 



from which we derive at once 



^=i-r"; 00 



^P ta 



this equation is the precise analogue of (29), p. 616 of 



* Subject to the restriction that for vapours the limits are less than 

 7r a0 , etc. 



Phil. Mag. S. 6. Vol. 33. No. 195. March 1917. T 



