SALTS OF ALBUMIN WITH BASES 



105 



of casein with regard to the equivalent conductivity, however, 

 leaves no doubt that this is an ordinary case for the application 

 of Ostwald's rule. Further, the relation emphasised by 

 Bodlander and Storbeck that the degree of dissociation of a salt 

 of (n -+- i) ions is the nth power of the degree of dissociation of 

 a salt of (i -+- i) ions, although of restricted application, gives 

 the value n = 3 for the valency of the caseinate ions when 

 sodium caseinate is compared with sodium bromide and sodium 

 chloride. 



The experimental determination of the valency of the casein- 

 ate ion by the osmotic pressure presents no mathematical 

 difficulty when the degree of dissociation is known. It is, 

 however, rendered impossible by disturbances due to hydro- 

 lysis which, in conse- 

 quence of the constant 

 dialysis of even small 

 quantities of alkali, 

 increases so much that 

 usually after twelve 

 hours a separation 

 and even precipitation 

 of casein set free by 

 hydrolysis makes its appearance. Under these conditions, the 

 molecular weight calculated from the osmotic pressure is 

 invariably too high. 



Electrometric measurements have shown that of the proteins 

 thus investigated casein is distinguished by a quite extra- 

 ordinary capacity for combining with alkali in excess of the 

 alkaline solution. A value of 10 milligram equivalents of alkali 

 hydroxide per gram of casein can be attained, corresponding to 

 a value of 100 for the equivalent of the casein ; and so, as a 

 valency of three is deduced from the experiments in which a 

 gram of casein combines with 0-9 millimols of sodium hydroxide, 

 the maximum valency displayed when saturated with alkali is, 

 in round figures, thirty. 



This high value for the combining capacity of casein is 

 obtained from the work of Pauli and F. Kryz quoted below, in 

 which, however, there is some uncertainty in the values for 



6 8 



FIG. 24 (Table 53). 



10 JO 



