238 HYDROGEN ION CONCENTRATION 



Since this will occur in the state of equilibrium, no work will be per- 

 formed. Finally, we shall dilute our solution, again by means of the 

 osmotic piston, to its original concentration, whereby the amount of 

 work, (n + 1) RT In Co, will be gained, since there are now n + 1 

 mols of acetone in the solution. The algebraic sum of the work ex- 

 pended and gained gives the amount of work gained, RT In — . Thus 



the amount of work depends upon the ratio of the given concentration 

 to the concentration at equiUbrium. 



When an electrolyte, such as HCl, is adsorbed, a similar process 

 takes place. The easily adsorbable H-ion must carry along with it 

 the less easily adsorbable Cl-ion, so that more of Cl~ is adsorbed than 

 would correspond to the true Cl~ adsorption equiUbrium. To ac- 

 complish this a certain amount of work must be apphed, which 

 depends upon the ratio of the given Cl~ concentration of the solu- 

 tion to that Cl~ concentration which would correspond to the specific 

 Cl~ adsorption equiUbrium. When a definite amount of Cl~ had 

 been carried along upon the charcoal surface, then the value of the 

 ratio of the original Cl~ concentration to the final concentration 

 approaches the closer to 1 the greater the Cl~ concentration. There- 

 fore, the H-ions can cany along the necessary Cl-ions out of a solution 

 rich in Cl~ almost without an expenditure of energy, and the true 

 adsorption equilibrium of H-ions is thus established. If this theory 

 is correct, the adsorption of HCl should be increased through the 

 addition of KCl. This has been experunentally confirmed.^ This 

 result was not one to be expected as a matter of course. For hitherto 

 it had always been observed that the presence of another substance 

 decreased the adsorption of the first substance ("adsorption- 

 displacement")^ while in this instance the very opposite was the case. 

 By constantly increasing the concentration of the added KCl in a 

 0.01 A'' HCl solution a limiting value for the adsorption of the HCl 

 is reached which represents the true adsorption equilibrium of the 

 H-ions. The theory was confirmed by finding that the adsorption of 

 HNO3 when accompanied by an increasing concentration of KNO3 

 led to the same limiting value for H+-adsorption. In the same 



s Rona and Michaelis, Bioch. Zeitschr. 97, 85 (1919). 



« Michaelis and Rona, Bioch. Zeitschr. 15, 196 (1908) ; 16, 489 (1909) ; Masius, 

 tJber die Adsorption in Gemischen. Diss. Leipzig 1908; Freundlich and Mas- 

 ius, Gedenkboek van Bemmelen 1910. 



