EQUILIBRIA IN ABSORPTION PROCESSES 155 



ponin and cholesterin, which acts as an antitoxin against 

 saponin. 



Even tetanolysin sometimes gives such maxima of effect 

 for a certain concentration, if the time of action is rela- 

 tively short. After a prolonged action the maximum dis- 

 appears. This maximum seems therefore to be related to 

 the velocity of the reaction and not to the final equilibrium. 

 Probably the same would occur also with the saponin if 

 its action could be prolonged for a sufficient time. 



Reactions of this kind are often explained as due to the 

 presence in the mixture of two substances of inverse effect. 

 Thus it is supposed that agglutinin treated with acids, etc., 

 contains, besides the real agglutinin, a substance called 

 agglutinoid, which hinders the agglutination. At higher 

 concentrations the bacilli are supposed to absorb chiefly 

 the agglutinoid and not the agglutinin ; at lower concen- 

 trations both are supposed to be absorbed. This explica- 

 tion seems to me to have no advantage, to mean no more 

 than the relation of the simple fact itself, besides being 

 much more difficult to remember. Furthermore, it seems 

 more simple to suppose that the reacting substance exerts 

 two different actions on the cells, of which the one, appear- 

 ing at higher concentrations, hinders the other, prevailing 

 at lower concentrations. Such a behaviour is not rare in 

 common chemistry. Thus, for instance, the addition of 

 alkali to a solution of aluminium chloride gives a precipi- 

 tate of aluminium hydrate, which is dissolved on further 

 addition of alkali. 



In a brochure dealing with the properties of colloids Biltz 1 



1 Biltz: Gottinger Nachrichten, math.-phys. Klasse 1904, I, Zeitschr. f. 

 ph. Ch. 48. 615 (1904). 



