﻿700 Mr. D. C. Henry on a 



Adsorption from Solution. 



The derivation of the adsorption relations used above 

 depends on the kinetic theory of gases, and cannot be applied 

 to adsorption from solution. It appears, however, to be a 

 thermodynamic necessity that an adsorbent which is in 

 equilibrium with a (mixed) liquid phase, should also be in 

 equilibrium with the saturated vapour phase above the liquid. 

 Williams * has found experimental confirmation of this 

 assumption, and I am at present carrying out further experi- 

 ments to test it. If it is valid, the adsorption equilibrium in 

 solution is determined by a combination of equations (6) with 

 the vapour pressure relations of the solution. Duhem's 

 equation and Margule's integration of it both lead to ex- 

 pressions too complicated to test experimentally, but the 

 special cases of (1) a dilute binary mixture, and (2) a mixture 

 giving a linear vapour pressure-concentration curve (Dole- 

 zalek's normal mixtures) may be amenable to experimental 

 verification. 



Adsorption from dilute solutions. 



For a dilute solution, we have for the solute, by Henry's 

 law, 



p^k^ (cj denotes volume concentration), 



and for the solvent, by Raoult's law, if P 2 is the vapour 

 pressure of pure solvent, 



8 -p == Cx (Ci denotes molecular concentration") 



= i-c 2 , 



so that j p 2 = P 2 C 2 . 



Now in dilute solution, both c and C are practically pro- 

 portional to 7j, the concentration in grams per gram solution. 

 Combining with equation (6), transforming the unit of 

 amount adsorbed to grams, and collecting the constants, we 

 get 



7 f"i u -i Uzl" 2 



where m 1s u 2 represent the true adsorptions of solute and 

 solvent respectively, uj' and u 2 ' the corresponding saturation 



* Williams Medd. f. K. Vet.-Akad. Nobelinstitut, ii. No. 27, p. 2. 



