RELATIVE MASSES OF PROTEIN IONS 



185 



equal. Equal numbers of protein ions must therefore migrate 

 to the anode and to the cathode respectively. Now since only 

 one of these ions is precipitated it would appear possible to de- 

 termine whether or not they are of equal weight by measuring 

 the change in concentration at the anodal and cathodal regions. 

 Employing Hittorf's method of representation, in the accompany- 

 ing diagram let the region to the right represent the cathodal and 

 that to the left the anodal region. Let the black spots repre- 

 sent anions and the white cations. The initial state of the solu- 

 tion is represented by the first double row of spots and its final 

 condition, after the decomposition of six molecules by the current, 

 by the second double row of spots. 



Since the velocities of the ions are presumed to be equal, the 

 number of undecomposed molecules of the original caseinate 

 must, after the passage of the current, be the same on each side. 

 The ions which have separated to the left (anions) have been 

 precipitated while those which have migrated to the right have 

 remained in solution. It is clear from the above diagram that 

 on the right six anions have been lost and six cations have been 

 gained. If they were equal in weight, therefore, it would appear 

 as if the concentration of casein in the right (cathodal) half should 

 remain unaltered by the passage of electricity. A moment's con- 

 sideration, however, will suffice to show that this is not correct. 

 In attaining this conclusion the assumption has been made that 

 the casein cations after reaching the cathode, no longer partici- 

 pate in the carrying of current. Unquestionably this is not the 

 case. As we shall see in the two succeeding chapters, the com- 

 bining capacity of casein increases markedly with increasing 



