662 



REVERSAL BY TRIVALENT CATIONS 



5.2 to 6.0, thereby proving that the Ce reversed the sign of the charge 

 of the gelatin film on the inside of the membrane without raising the 

 hydrogen ion concentration to that point where an acid reversal 

 occurs. In Fig. 3 m/ 1,024 AICI3 solutions are used for rendering the 

 membrane positive. In this case the pH was about 4.1 in all solutions. 



CD 



I 



c 

 g 



'to 



CD 



1 



.s 



c 



260 



240 



220 



ZOO 



180 



160 



140 



120 



100 



80 



60 



40 



20 







n ilHHHHHHllIIII 

 ^ 2048' 1024 512 256 126 64 32 16 8 4 



fin 



Concentration of KCl,NaCl,LiClandCaCl2 



Fig. 2. The relative influence of different cations upon the attraction of water 

 is in the erder Ca > Li > Na > K, proving that the membrane is positively 

 charged in the presence of Ce. 



The order of efficiency of cations remains the same as when CeCIs 

 is used, but the effect is quantitatively larger in Fig. 3 than in Fig. 2. 

 All these experiments and many others show that trivalent cations 

 cause the membrane previously treated with gelatin to be charged 

 positively on the alkaline side of the isoelectric point of gelatin. 



