no PHYSICAL CHEMISTRY 



Bethe and Toropoff found that polyvalent cations tend to 

 reverse the charge of the membrane and, hence, the direction 

 of electroendosmose and disturbance of neutrality, whereas poly- 

 valent anions tend to maintain it. The effectiveness of anions 

 in causing cathodic acidity is as follows: citrate'" > phos- 

 phate'^ oxalate" > SO,"> I'> Br'> Cl'> NO,'. The ef- 

 fectiveness of the cations in reversing the charge of the membrane 

 and disturbance of neutrality is as follows: Co(NH 3 ) 6 ""> 

 La"-:> Ca ;- > Ba"> Mg"> Na ; > Os ; > Kj> Li<> NH 4 <\ 



The experiments of Bethe on living cells (1916) are, however, 

 open to another interpretation. It was shown (McClendon, 

 1914 d) that the anthocyan (or other pigment) in many plant 

 cells is amphoteric. In acid it is red and goes to the cathode, 

 whereas in alkali it is blue or green and goes to the anode, if an 

 electric current is passed through the solution. These changes 

 may be observed in the living cells, which are penetrated easily 

 by acetic acid or ammonia but are easily injured by the reagent 

 or current so that the pigment passes out of them. In successful 

 experiments, all of the pigment is massed in the cathode ends 

 of red cells and in the anode ends of blue cells. When the plant 

 is fresh the pigment is usually reddish, but contains a small pro- 

 portion of blue, and sometimes violet cells may be found. If 

 an electric' current is carefully passed through a violet or red- 

 violet cell under the microscope, the red portion of the pigment 

 will mass in the cathode end of the cell, and the blue portion 

 in the anode end. This phenomenon may have led Bethe to 

 suppose that the passage of the current through the membrane 

 disturbed the reaction. His experiments on cells stained with 

 neutral red are not, however, open to this objection. It should 

 be noted that the anode end of the cell is the cathode side of 

 the membrane against which the pigment is massed. 



It might be supposed that the colloidal membranes used by 

 Bethe and Toropoff are so different from the porcelain used by 

 Bartell that the results may not be compared. Bethe and Toro- 

 poff found, however, that membranes of clay or carbon behaved 

 in the same way as gelatine membranes, in the disturbance of 

 neutrality on the passage of an electric current through them. 

 We may, therefore, safely use the foregoing findings in ex- 

 plaining the results obtained with various membranes. Flusin 



