186 ELECTROCHEMISTRY 



alkalinity of its solution, at first in direct proportion, each fresh 

 equivalent of combined alkali splitting another — N.HOC— union. 

 Therefore the potassium or other metal which is transported 

 along with the casein to the cathode, on being transformed there 

 into the hydrate, will split the ion with which it has travelled 

 into two, thus: 



H2N.R1.COH.N.R2.COK + 2 H2O 



= H2N.R1.COH.NR2.COOH + KOH + H2 



H2N.R1.COH.N.R2.COOH + KOH H 



= H2N.R1.COK + ^N.R2.C00H 



I 

 OH 



the resultant cation may be presumed to be retained in the cath- 

 ode region while the anion migrates to the anodal region. Each 

 cation which the cathodal region gains, therefore, yields up, 

 provided the masses of the cations and anions are in every case 

 equal, one-half of its mass to the anodal region again. Referring 

 to the diagram again, therefore, the true gain by the cathodal 

 region will be only half of that represented, equal in weight to 

 only three of the six ions which have been deposited on the anode, 

 while its loss will have been three molecules, together equal to 

 the total weight of casein deposited on the anode. Provided, 

 therefore, the anions and cations in a solution of potassium 

 caseinate are equal in weight, no matter what their absolute 

 weight, then it is clear that the loss of casein from the cathodal 

 region must be exactly half the loss from the anodal region. 



I have endeavored to test this theoretical conclusion by de- 

 termining the loss of casein from the anodal and cathodal limbs 

 of the U-tube employed in the experiments described in the 

 preceding section of this chapter. The following are some ex- 

 perimental results. The measurements of the amounts of casein 

 were made by means of the refractometer, as described in the 

 preceding section. 



(1) Solution of 3.75 per cent casein in 0.03 N KOH; neutral to phenol- 

 phthalein. 

 Electrolysis for 2 hours at 30 degrees. Current approx. 1 milliampere. 

 Gram of casein lost from the anodal arm . 062 ± . 007 



Gram of casein lost from the cathodal arm . 036 =b . 009 



Ratio 1.9 ±0.7 



