ADSORPTION PHENOMENA 211 



adsorption, from the electrocapillary part. From some rough 

 calculations made by the writer (Zeitsch. Phys. Chem., 73, 129, 

 (1910)) it appeared that the electro-capillary term was approxi- 

 mately one- tenth that of the capillary. 



A further point in this connection may be mentioned. It 

 is well known that, on plotting potential difference against 

 surface tension, when the applied P.D. opposes the naturally 

 existing one, the tension passes through a maximum, which 

 possibly coincides with the removal of the charge. At the 



maximum point the value of -^ is zero, and hence under these 



air 



conditions we are necessarily dealing with a pure capillary 

 effect. No attempt, however, has been made to investigate 

 the adsorption under such conditions, and indeed the experi- 

 mental difficulties would appear to be well-nigh insuperable. 

 Our knowledge of adsorption must therefore be regarded at 

 the present time as limited to purely capillary effects. The 

 progress which has been made, though not extensive, is of 

 very considerable importance, not only for the theory of 

 capillarity itself, but equally so for physiological and bio- 

 chemical problems. 



