JACQUES LOEB 



575 



(which took place to the cathode) was observed. The curves in Fig. 8 

 show the result. The quantity of transport of liquid was depressed 

 both by the addition of KCl and of CaCla but more by CaCl2 than by 

 KCl. The addition of 0.1 cc. of m/4 CaCl2 to 100 cc. of m/512 NaaSO^ 

 (concentration of CaCl2 = m/4,000) lowers the transport of water 

 more than twice as much as the addition of 0.1 cc. of m/4 KCl, The 

 depressing influence of the addition of KCl or CaCl2 in the electrical 

 transport of water through a collodion membrane can be demon- 

 strated equally well with m/256 solutions of Na2S04 as with m/512 

 solutions. 



I 



I 



-•— » 

 o 



•4— • 



o 



o 



I 



10 



•^ 4^2500 1000 50D 250 125 



Concentration o[ KCl and CaCl^ 



Fig. 8. Electrical endosmose. Showing that a similar depressing effect as in 

 Fig. 7 exists in the case of electrical endosmose. 



These experiments on electrical endosmose show that the density of 

 negative charge on the membrane in contact with a m/256 or m/512 

 Na2S04 solution is diminished by the addition of any electrolyte 

 (whose anion does not act more powerfully than SO4) and that the 

 diminution increases with increase in the valency of the cation added. 

 This furnishes the explanation of the fact that when m/256 Na2S04 

 is separated from pure water by a collodion membrane the rate of 

 diffusion of the positively charged water into the solution is dimin- 

 ished by the addition of KCl and still more by the addition of 

 MgCla or CaCl2. 



