ADSORPTION POTENTIALS AND ELECTROKINETIC PHENOMENA 235 



found to be the same as before. Hence we must conclude that the 

 adsorption properties of an electrolyte are additive functions of those 

 of its anions and cations. But also the nature of the adsorbent as 

 well as of the solvent, has an influence upon the process of adsorp- 

 tion. Therefore, in an experimental study, we must vary the adsorb- 

 ent, the cation and the anion. For the adsorbent we shall choose 

 for the present charcoal,^ which is the prototype of the so-called 

 chemically indifferent adsorbing agents, and we shall vars^ the anions 

 and the cations. 



After some preliminary experiments with Lachs, the author in 

 collaboration with Rona^ has carried out a systematic series of in- 

 vestigations and has obtained the following results. 



Of the neutral salts all, with the exception of the sulfates of the 

 alkali metals, were adsorbed to an analytically demonstrable extent. 

 In all cases of true neutral salts equal amounts of cation and anion 

 were adsorbed, no measurable amount of hydrolytic splitting having 

 occurred in the adsorption of true neutral salts. The adsorption of a 

 salt appeared as an additive property of its ions, thus, for instance, 

 all sulfocyanates were more strongly adsorbed than the corresponding 

 chlorides. 



Consequently the anions and cations can be arranged in series ac- 

 cording to their adsorbabilities. In such series we can also include 

 the H- and OH-ions, by simply comparing the adsorption of HCl 

 with that of other chlorides and bj^ comparing the adsorption of 

 NaOH with that of other Na-salts of equivalent concentrations. 

 These series are 

 Cations: 



Na"*" I Organic dye bases 



K+ Ca++ Mg++ Al^++ Cu++ H+ 

 NH4+J Ag+ 



Anions: 



SO? CI- Br- I- SCN- OH- 



Organic dye acids 



' Blood charcoal will always be understood. Retort-, sugar- and other 

 charcoals do not show the same uniform behavior. 



2 Lachs and Michaelis, KoU.-Z. 9, 275 (1911) ; Zeitschr. f. Elektrochemie 17, 

 1 and 917 (1911); Rona and Michaelis, Bioch. Zeitschr. 94, 240; 97, 85; 103, 

 19 (1920) ; Michaelis and Rona, Bioch. Zeitschr. 94, 225; 97, 57; 102, 268 (1920) : 

 KoUoid-Zeitschr. 25, 225 (1919). 



