DILUTION 235 



diacid bases are insoluble in water (11) (25). All of these differ- 

 ences, it will be observed, suggest more or less strongly that the 

 molecules of the caseinates of the alkaline earths are of greater 

 size and more ponderous than those of the caseinates of the 

 alkalies. 



Assuming, therefore, that p = 2 for the salts of the alkalies 

 and 1 for the salts of the alkaline earths we find that the numer- 

 ical values of p (w + v) in Tables XXIV and XXV accord very 

 well with our knowledge of the mobilities of heavy ions. The 

 average value oi u -\- v at 30 degrees for potassium caseinate 

 containing 80 X 10~^ equivalents of KOH per gram is 42 X 10~^ 

 cm. per sec, while for the salts of the alkaline earths at the same 

 temperature the average value oi u -i- v is 38 X 10~^. Assuming 

 the migration velocities of the anions and cations to be equal 

 (since, as we have seen, their masses are nearly equal) the equiv- 

 alent velocity of a protein ion at 30 degrees would appear to be 

 about 20 X 10~^ cm. per sec. under a potential gradient of 1 volt 

 per centimeter. Now Bredig (1) has shown that the equivalent 

 velocities of heavy ions tend to attain, with increasing weight, 

 a constant minimum value of about 15 X 10~^ cm. per sec. at 

 15 degrees. At 30 degrees this velocity would be increased by 

 about 30 per cent, i.e., would become 20 X 10~^ cm. per sec. 



Referring to Table XXVI it is evident that p (u -\- v) is much 

 larger for the salts which proteins form with acids than it is 

 for the salts which they form with bases. It is about twice as 

 large, in the case of serum globulin, as it is for the salts of diacid 

 bases. We can hardly assume that the migration-velocity of 

 protein ions is twice as great in acid as in alkaline solution and 

 we must therefore adopt the alternative assumption that p is 

 twice as great in acid as in alkaline solutions. This might arise 

 by the spUtting of double — COH.N— bonds, thus: 



H CI 



++ \ / 

 -COH.N. -COH ^N. 



^R-fHCl-KH20= ++ + )r 

 -COH.N -^ -COH ^N^ 



H OH 



which indicates that, as Kossel has suggested (3) the active 

 agents in bringing about the neutralization of acids by proteins 



