90 PROTOPLASMIC ACTION AND NERVOUS ACTION 



point. The H-ion concentration corresponding to this 

 neutral position varies according to the special chemical 

 character of the material and its adsorbent properties. 



Various chemical effects apparently depending on 

 unequal adsorption of ions are described in Freundlich's 

 book; frequently these appear to be consequences of the 

 displacement of one ion from an adsorbent surface by 

 another which is more readily adsorbed. For example, 

 many basic dyes (crystal violet or basic fuchsin) are 

 chlorides of organic color-bases; when these dyes are 

 adsorbed by charcoal, a large part of the combined 

 chloride goes into solution as inorganic chloride. This 

 result is explained by Freundlich as due to the high 

 adsorbability of the color cation (dye-HCl = dye-H+ 

 and Cl~) which displaces from the adsorbent the adsorbed 

 cation;^ according to this view the chemical splitting is 

 due to the unequal adsorbability of the two ions. The 

 phenomenon may, however, be regarded as a consequence 

 of the high adsorbability of the free base, which is present 

 in the solution in consequence of partial hydrolysis; this 

 base is removed, leaving the chloride in solution.^ It is 

 known that many organic free bases are more highly sur- 

 face-active (adsorbed) than the salts; thus Traube points 

 out that the surface-tension of solutions of hydrochlorides 

 of the alkaloids, cocain, atropin, and quinine is lowered 

 by adding a little alkali, an effect due to the liberation 

 of the free base;^ the latter will tend to be adsorbed and 

 the hydrolysis will be promoted. The separation of 



^ Freundlich, op. ciL, p. i68. 



* Cf. Michaelis, Arch. ges. Physiol., XCVII (1903), 634. 



3 Traube, Kolloidchem. Beihefte, III (191 2), 237; cf. also Hober, 

 op. cit., p. 215. 



