24 ELECTRIC CHARGE ON NATURAL SOLUBLE 



Bredig. The amphoteric electrolytes are generally asymmetrical 

 with respect to their power of dissociating into H- or OH' ions, 

 for either the acidity or the basicity is predominant. Only 

 water, which dissociates H 2 O < > H- -f OH' is symmetrically 

 amphoteric. 



The application of the law of mass action to amphoteric 

 electrolytes by G. Bredig, J. Walker and H. Lunden * has 

 resulted in the development of a theory applicable to them 

 which has proved particularly fruitful in dealing with the 

 proteins. We will next give some applications of the mass 

 action law to electrolytes, which we shall have to use repeatedly. 



The dissociation of an acid, e.g., the weak and slightly ionised 



acetic acid CH 3 . COOH : " H- + CH 3 . COO' is expressed 



by the equation C H . X C C H 8 coo' = K X C C H 3 cooH, where C is 

 the molecular concentration of the various substances, and K 

 is the dissociation constant of acetic acid. The value of K for 

 a weak electrolyte is largely independent of dilution (W. 

 Ostwald). This equation holds for every solution, provided 

 the proper molecular values are inserted, in this case those for 

 the acetation, hydrion and undissociated acetic acid. If the 

 product on the left hand of the equation is increased by a rise 

 in the concentration of acetations or hydrions, the proportion 

 of undissociated acetic acid molecules is increased, as its ionisa- 

 tion is suppressed. As the acetates of the alkali metals are 

 ionised to a great extent in solution, the concentration of 

 acetate ions can be increased by adding them to the solution ; 

 while the hydrion concentration can be made larger by the 

 addition of strong acids, such as hydrochloric acid. In general, 

 the ionisation of a weak electrolyte is reduced by adding a strong 

 electrolyte with a common ion. Compared with it, the converse 

 effect of the weak electrolyte on the ionisation of the strong 

 electrolyte completely disappears. 



Such mixtures of a weak electrolyte with a corresponding 

 strong electrolyte with a common ion, e.g., acetic acid -acetate 

 mixture, or the combination ammonium hydroxide ammonium 

 chloride, have an important distinctive property which is 



* H. Lunden, " Affinitatsmessungen an schwachen Sauren u. Basen." 

 Stuttgart. F. Enke. 1908. (Literature.) 



