SALTS OF ALBUMIN WITH BASES 



103 



For sodium caseinate the value A^, = w Na -(- ^casein = 81 is 

 obtained by the graphical method ; for ammonium caseinate 

 ^ = NH 4 + ^casein = 104- Thus the difference, w NHl *%a = 23. 

 The actual difference in the mobility of these two ions at 25 is 

 74-4 -- 50-9 = 23-5. This agreement is seen to be a certain 

 indication of the formation of typically ionised alkali caseinates. 

 In the same way the almost equal values of the mobility of the 

 potassium ion (u K iS = 64-6) and the ammonium ion (u^ H ^S = 

 64-0) agree well with the results obtained for the equivalent 

 conductivity of ammonium and potassium caseinates. 



Table 51. 



As the difference of the equivalent conductivity,* A = 

 ac.(u -j- v), of two caseinates with different ions is, e.g., A K .c as 

 ANa . cas = a (U K Na) the value calculated for i per cent, casein- 

 ate solutions, the degree of dissociation being 0-66, is A K .cas 

 ^Na . cas = 13*9- Direct experiment gives the value 14-13 (Pauli, 

 loc. cit., p. 499). These results are undeniable evidence of the 

 existence of alkali caseinates, which dissociate into alkali metal 

 ions and caseinate ions. 



The mobility of the caseinate ion, calculated from the A^ 

 of the alkali caseinate, is z; Cas =30-1. This value is entirely 

 within the range of mobility shown by numerous organic ions. 

 We shall return later to the importance of high valency and 

 large atomicity in regard to the mobility of the ion. 



With a knowledge of the equivalent conductivity of the 

 caseinates and of their regular behaviour, it is possible to 



* The pertinent observation of Pauli (loc. cit.} that a practically 

 complete dissociation of the caseinate occurs is justified by a con- 

 sideration of the degree of dissociation. 



