JACQUES LOEB 573 



a transport of water to the anode occurs which increases with in- 

 creasing concentration to about m/512 provided the membrane had 

 been treated with a protein (upper curve, Fig. 6) ; when the collodion 

 membrane has not been treated with a protein no such migration 

 occurs (lower curve, Fig. 6). Hence the curves for electro-endosmotic 

 transport of liquid through collodion membranes and the transport 

 of water in free osmosis run parallel, supporting the explanation 

 offered. 



In comparing the upper curves in Figs. 5 and 6, the reader will 

 notice a difference, inasmuch as in the case of free osmosis through 

 membranes treated with gelatin (upper curve. Fig. 5) the curve shows 

 only a rise but no drop, while in the upper curve for electro-endos- 

 motic transport (Fig. 6) through a gelatin-treated membrane in the 

 presence of a solution of AICI3 there occurs the characteristic drop at a 

 concentration beyond m/512. The writer is inclined to attribute the 

 reason for this difference to the fact that in free osmosis the gas 

 pressure effect prevents the drop while in electrical endosmose this gas 

 pressure effect is excluded (since the solutions on both sides of the 

 membrane are identical) . 



IV. 



When we separate a m/256 solution of Na2S04 or Li2S04 by a 

 collodion membrane from pure water, the latter will diffuse into the 

 solution with a certain velocity. When we add small and identical 

 quantities of a salt hke KCl to the solution of m/256 Na2S04 and to 

 the distilled water, this velocity will be diminished;^ owing to, the fact 

 that beyond a concentration of m/256 Na2S04 the repelling or de- 

 pressing effect of the cation of the solute increases more rapidly 

 with increasing concentration of the electrolyte than the attracting or 

 accelerating effect of the anion on the rate of diffusion. When we 

 add MgCl2 or CaCl2 instead of KCl the depressing effect is still 

 greater than in the case of KCl, owing to the fact that Mg and Ca, 

 as bivalent ions, have a greater depressing effect than K. Fig. 7 

 illustrates this statement, showing that the addition of KCl or MgClg 

 or CaCl2 to m/256 Na2S04 diminishes the rate of diffusion of liquid 

 into the Na2S04 solution and that MgCl2 and CaCl2 act more power- 



« Loeb, J., /. Gen. Physiol, 1919-20, ii, 273. 



