GENERAL CHEMISTRY OP MILK 87 



dilute alkalies and their carbonates and alkaline earths; such solu- 

 tion should not give the Molisch reaction. Solutions in alkalies 

 are slightly opalescent; in alkaline earths, milky. Casein replaces 

 CO2 in carbonates, yields no ash on combustion, and has never 

 been crystallized. 



The following elementary analyses of caseins from different 

 sources are given by Tangle: 



Animal. 



Cow 



Buffalo 



Goat . , 

 Mare. 



Ass... 



Richmond gives the following formulae and compositions of 

 bovine casein: 



FORMULAE AND COMPOSITION OF CASEIN 



Cl62H26sN4lSP062. Cl7oH268N42SP06>- 



C 52 . 96 per cent. 54 , 04 per cent. 



H 7.03 " 7.10 



N 15.64 " 15.56 



S 0.86 " 0.84 



P 0.84 " 0.82 



22.41 " 21.60 



Different properties of caseins are shown by the following facts: 



1. The combining power of different caseins is not the same. 

 The following values are given by Raudnitz, compiled from various 

 sources: 



Equivalent. 



Bovine casein 1124-1135 



Goat casein 1190 



Human casein 1200-1428 



Ass's casein 1504 



2. Electric conductivity and specific rotatory power differ in 

 caseins from different animals. 



3. Human casein and casein from the milk of solipeds is more 

 readily soluble than caseins from ruminants. The precipitate of 

 the former is in finer flakes than that of the latter. According to 

 Richmond, the casein of ruminants is combined with phosphates 

 and alkaline earths, while the casein of solipeds and human casein 

 are combined with alkaline earths. 



4. Caseins produce specific antibodies, precipitins, for example, 

 so the fundamental differences can be demonstrated by immunity 

 reactions. 



On the other hand, there are some properties which are com- 

 mon to all caseins. They all contain phosphoric acid, but do not 

 yield the decomposition products of nucleoproteins. Casein is, 

 therefore, classified with the phosphoproteins. Furthermore, all 

 caseins are precipitated from their calcium combinations by rennet. 



Cow casein is a white, amorphous, hygroscopic powder, with- 



