88 PROTOPLASMIC ACTION AND NERVOUS ACTION 



(influence of salts on surface tension, solubility, vis- 

 cosity, catalytic action, etc.).^ 



ADSORPTION OF IONS 



The difference between the adsorbability of the two 

 ions of an electrolyte implies an influence on the potential 

 difference at the phase-boundary; the surface receives 

 the charge of the raore adsorbable ion and the adjacent 

 layer of solution the opposite charge. Potentials 

 arising in this way have been called "adsorption poten- 

 tials" by Freundlich,^ and they undoubtedly play an 

 important part in colloidal phenomena, since the altera- 

 tion of the surface charge is a chief factor in the changes 

 of aggregation-state and other phenomena characteristic 

 of colloids. Adsorption potentials may also be of great 

 importance in influencing the character of the chemical 

 changes occurring under the catalytic influence of 

 surfaces. 



There are many indications that the ions of water, 

 OH and H, are among the most readily adsorbed ions. 

 This property is of special biological importance, since 

 most forms of protoplasm are highly sensitive to varia- 

 tions in the concentration of these ions; and in certain 

 cases this sensitivity has become a regulatory factor of 

 the utmost delicacy. Free organic acids and bases are 



^ For a summary of the physical effects of salts showing the lyotropic 

 series cf. Hober, op. cit., p. 310. 



^ According to Freundlich the adsorption potential is not the poten- 

 tial between the interior of the solid phase and the adjoining solution, 

 but that between an adhering immobile layer of solution and the mobile 

 layer adjoining. Cf. Kapillarchemie, p. 243; also Report on the Physics 

 and Chemistry of Colloids by the Faraday Society and the Physical 

 Society of London (192 1), p. 146. 



