These numbers show that there is some kind of 'affinity' between 

 the bodies adsorbed and those which take them up. Put in other 

 words the law states that there is not a proportionality between the 

 concentration of the solution or partial pressure of the solute and the 

 amount adsorbed. Ostwald ' indeed points out that there is no hard 

 and fast distinction to be drawn hetween chemical affinity and adsorption 

 which lattter he sometimes speaks of as c mechanical affinity.' He 

 calls attention to the complete series of transitions between the two 

 phenomena, and, in referring to Van Bemmelen's researches, he 

 remarks that they frequently leave it a matter of uncertainty as to 

 whether the facts brought forward should be regarded as of a chemical 

 or physical nature. In any case all the evidence shows that electrolytes 

 when adsorbed are non-ionized and no longer take part in the electrical 

 conductivity of the solution. This circumstance renders the determin- 

 ation of conductivities a rapid and convenient method of investigating 

 certain aspects of the problem as will be seen later. 



In the course of a scries of experiments on the changes of con- 

 ductivity in protein solutions brought about by the action of enzymes 

 I have had occasion to take into consideration the possibility of the 

 splitting-off of inorganic electrolytes under these conditions. The 

 results of some preliminary experiments suggested to me that the most 

 satisfactory explanation of the nature of the ' combination ' between 

 protein and ash was that the constituents of the latter are present in 

 adsorbed form rather than in true chemical union. 



Before passing on to the description of the experiments made to 

 throw light on this problem, 1 may, in order to make clear the point 

 of view, give the results of a preliminary experiment on an undoubted 

 case of adsorption, viz., congo-red and filter-paper. 



Experiment : Seven flasks were taken, each containing 50 c.c. of a 

 solution of congo-red in 10 per cent, alcohol. These solutions were of 

 a regularly diminishing concentration from 0-014 to O'OO2 per cent. 

 Congo-red forming a colloidal solution is very readily precipitated 

 from watery solution by traces of electrolytes, so that an alcoholic 



I. Lehrbuch d. Allgem. Chimie., ite. Aufl. Bd. I, p. 1084, et seqq. 



