234 



HYDROGEN ION CONCENTRATION 



lation in the surface layer as adsorption. If it is desired to differen- 

 tiate such an adsorption as described above from the usual mode, 

 it could be designated as ''apparent adsorption.'' In these terms 

 the empty space becomes also an adsorbent. And thus this definition 

 facilitates the formal explanation of the phenomena of adsorption. 



65. The adsorption of electrolytes by charcoal 



The problem reduced to its simplest form relates to the adsorption 

 of the individual ionic species. But since it is impossible to obtain a 

 solution of an individual ionic species, and since we can only have a 



TABLE 37 



SOi 



ci- 



CNS- 



OH- 



With 0.05 A^ solutions 



Na+.... 

 NH4+ .. 



3 

 H+. 











16 



47 



70 



11 

 11 



35 



73 



68 



solution of one electrolyte, i.e., a mixture of a negatively charged and 

 a positively charged species of ions, so that actually we can only 

 investigate experimentally the adsorption of the entire electrolyte 

 molecule, and any statement concerning the adsorption of a single 

 ionic species, which completely escapes chemical analysis, can be 

 made only by inference, and with greater or lesser certainty. Thus 

 we find, for instance, in studying the adsorption of different sodium 

 salts (NaCl, NaBr, Nal, etc.) certain quantitative differences. Now 

 if we study the calcium salts of the same anions, we find other ab- 

 solute values, but the relative differences in the series of anions are 



