SALTS OF ALBUMIN WITH BASES 



109 



increasing quantities of the same solution of base are added, 

 there is a moderate increase in conductivity up to a dilution 

 of one half. Beyond that point the equivalent conductivity 

 increases rapidly owing to increasing valency and consequent 

 increase in mobility of the ions. This is shown by the following 

 results, in which the free alkali is taken into consideration. The 

 corresponding curve (Fig. 26), which must be read from right to 

 left, shows a sharp break when the dilution becomes greater than 

 one half (between 0-4 and 0-6). 



Table 57 (Fig. 26). 



2-01 per cent, dry casein in 100 c.c. o-oi N NaOH, progressively 

 diluted with o-oi N NaOH. 



* Corrected values. 



These results all become explicable without difficulty when 

 the following view is adopted. A neutral salt exists, composed 

 of approximately i millimol of alkali and i gm. of casein, the 

 ion being trivalent, viz. : 



Na 3 . (Caseinate)"' (I.) 



This salt can form a typical complex salt by addition of a 

 molecule of casein : 



Na 3 . (Caseinate)'". (Casein) (II.) 



the valency remaining unaltered. Addition of alkali converts 

 salt (II.) into salt (I.) with moderate increase in conductivity, the 

 valency remaining constant. The equivalent weight of casein 

 calculated from these results is 1,000, somewhat lower than the 

 value obtained by Laqueur and Sackur, giving a molecular 

 weight of 3,000. Probably the alkali salts of the globulins and 

 of the acid-albumins behave in a similar way to that of casein, 

 which, however, is particularly suitable for experiment owing 

 to the abundance of its acid valencies. 



