574 



CAUSE OF INFLUENCE OF IONS. H 



fuUy than KCl. The addition of 0.2 cc. of m/4 MgCla or CaCla to 

 100 cc. of m/256 Na2S04 (concentration of MgCl2 or CaCla = m/2,000) 

 lowers the rate of diffusion of water into the solution more than 50 

 per cent, while the effect of the addition of 0.2 cc. of m/4 KCl (con- 

 centration of KCl = m/2,000) lowers the rate of diffusion of water 

 into the solution considerably less. 



^ 4000 2000 1000 500 250 125 62 31 16 



Concentration of KCl, NgCl^ and CaCl2 



Fig. 7. Free osmosis. Depressing effect of the addition of KCl, MgCl2, and 

 CaCla upon the attraction of water by m /256 Na2S04. 



Fig. 8 shows that the addition of KCl and CaCla to m/512 Na2S04 

 has the same depressing effect on the rate of transport of liquid 

 through the collodion membrane in the case of electrical endosmose. 

 In this, as in the preceding experiments on electrical endosmose, iden- 

 tical solutions were put into both sides of the collodion membrane. 

 These solutions were m/512 Na2S04 alone or with the addition of small 

 quantities of KCl or CaCl2. A p.d. of 15 volts was produced on the 

 opposite sides of the membrane and the rate of transport of water 



