﻿702 



Mr. D. C. Henry 



in this way some results of Williams and of Gustafson *. 

 Though the agreement is not perfect, the straight line fits 

 the observations for low concentrations as well as any line. 



Fig. 6. 



lo S%. 



0-5 



00 



19 



00 



1 



loci 



U-i 



0-2. 



Gustafson's Observations on the Adsorption of a 

 Phenol- Alcohol Mixture. 



No observations are available for testing these relations 

 with a mixture of linear vapour pressure-concentration 

 curve. 



A Derivation of the u Exponential Formula "for the 

 Adsorption Isotherm. 

 i 



The relation a = kc n 



has hitherto had no theoretical basis, but represents experi- 

 mental results very well for Ionv concentrations. By a 

 method based on the same assumptions as those employed in 

 the earlier part of this paper, this formula can be put on a 

 theoretical basis. 



Consider the adsorption of a gas. Let the free surface 

 energy of the bare surface (i. e. the surface in contact with 

 a vacuum) be a Q ergs per sq. cm., and let the free surface 

 energy of the same surface covered with a monomolecular 

 layer of gas be cr^ In adsorption equilibrium, let a fraction 

 6 of surface be covered, and let the free energy of the whole 

 surface be a ergs per sq. cm. 



Then, since the range of molecular action is assumed 

 small, 



o- = o- o (l — d) + a l = <T o —(cr o ~o- 1 )0. 



* Gustafson, Zeit.f. Phys. Chem. xci. p. 

 :hem. xxi. p. 459 (1915). 



385 (1916) ; Zeit.f. Electro- 



