﻿704 



A Kinetic Theory of Adsorption. 



work the larger will n be. This is in accord with experi- 

 ment, for we find that the larger the molecule of adsorbate, 

 the larger is n, as exemplified by the following Table for 

 various substances adsorbed on charcoal. 



Table V. 



Gases. 



Hydrogen 



Nitrogen 



Oxygen 



Carbon Dioxide., 

 Sulphur Dioxide 

 Chlormethyl 



1 to 2 



2-47 (Chappuis) 



3-09 



8'2 



Solutes. 



Formic Acid 



Acetic Acid 



Propionic Acid 



Butyric Acid 



Benzoic Acid 



Picric Acid 



Benzenesulphonic Acid 



New Fuchsin 



Crystal Ponceau 



Cane Sugar 



2-22 

 2-35 

 254 

 332 



2-72 

 417 

 4-48 

 5-38 



6-67 



8-2 (Bancroft) 



(Data, except where specified, from 

 Freundlich, Kapillarchemie, p. 150.) 



We should expect that the value of W would increase in 

 the same sequence for a series of adsorbates on different ad- 

 sorbents, since the orientational work will be chiefly due to 

 orientation of the adsorbate molecules. This is approxi- 

 mately the case (Freundlich, Kapillarchemie, p. 155). 



It would be interesting to compare the values of W 

 obtained from the exponential formula with the work done 

 when two unit surfaces of two liquids come together 

 (Harkins *), but as far as 1 am aware, there are no experi- 

 mental data for the adsorption isotherm on liquid adsorbents. 



Summary. 



1. A theory of adsorption of gases has been developed on 

 a kinetic basis by means of assumptions derived from Lang- 

 muir's conception of a monomolecular layer. 



2. Equations for the adsorption isotherm and isostere 

 are deduced which are in satisfactory agreement with 

 experiment. 



3. A method is suggested for applying these equations to 

 adsorption from solution, and the results compared with 

 experimental data. 



* Harkins, Jour. Amer. Chem. Soc. xxxix. p. 541 (1917). 



