188 ELECTROCHEMISTRY 



placing above the solutions, in both arms of the U-tube, a solu- 

 tion of the acid or base employed to dissolve the protein. A 

 potential gradient was placed across the U-tube and it was ob- 

 served that in acid solutions both boundaries of the protein solu- 

 tion migrated towards the cathode, while in alkaline solutions 

 both boundaries of the protein solution migrated towards the 

 anode. The rate of migration varied between 7 to 10 X 10~^ cm. 

 per sec. for unit potential gradient when strong acids or bases 

 (HCl and NaOH) were employed and about 20 X 10~^ cm. per 

 sec. when a weak acid (acetic acid) was employed. Following 

 the view which I have developed of the mode of dissociation of 

 protein salts, it would appear as if the boundaries should move 

 in opposite directions at approximately equal velocities. A 

 moment's consideration of the method of measurement employed 

 by Hardy shows, however, that under the conditions of his ex- 

 periment this would not occur. At the boundary of the protein 

 solution (nearly neutral) and the HCl solution (for example) a 

 difference of potential of considerable magnitude would exist 

 owing to the much more rapid diffusion of H+ into the protein 

 solution than of CI'. This difference of potential would lower the 

 potential gradient at the cathodal boundary and raise it at the 

 anodal boundary. Bearing in mind the fact that the two protein 

 ions are possessed of the same equivalent migration-velocities 

 under unit potential fall, the effect of these inequalities in poten- 

 tial gradient must have been, at the anodal boundary, to urge 

 the protein anions toward the anode more rapidly than the cat- 

 ions were repelled from the boundary, and, at the cathodal bound- 

 ary, to repel the protein anions from the boundary into the protein 

 solution more rapidly than the cations crossed the boundary. 

 The net result of these processes would be, obviously, a migration 

 of the protein, as a whole, towards the anode. The contact- 

 differences of potential at the boundaries would be equal in 

 magnitude but opposite in sense and hence both boundaries 

 would migrate at the same velocity, but in the same direction. 

 The fact that the highest velocities were obtained when weak 

 acids (acetic) were employed, in which the difference between 

 the equivalent velocities of the ions (H+ and acetanion) is great- 

 est, strongly supports this interpretation of Hardy's results. 

 Alkali-globulin, in contact with alkaline solutions would, of 

 course, move as a whole, but somewhat more slowly (since the 



