10 MILK-ANALTSIS. 



incipient fermentation of the milk-sugar, decomposed this 

 hypothetical compound, and threw down insoluble caseine. 



This explanation must be abandoned, inasmuch as inves- 

 tigation has shown that the ash of milk is almost absolutely 

 devoid of alkali. In truth, we are driven to the conclusion, 

 that the change from soluble to insoluble caseine is molecu- 

 lar, resembhng the change from soluble silica to insoluble 

 silica. 



The ultimate composition of caseine is not distinguishable 

 from that of albumen and fibrine, viz. — 



Carbon ...... 53.7 



Hydrogen 7.1 



Nitrogen ..... 1.5.7 



Oxygen 23.5 



100.0 



There is likewise a trace of sulphur, said to be about one 

 per cent. In milk the caseine is chemically combined with 

 phosphate of Ume ; and there is no known method of effect- 

 ing a separation between the two without destroying the 

 caseine. 



Milk is coagulated — that is to say, the caseine is rendered 

 insoluble — ^by the action of rennet, of acid, and of many 

 metallic salts. 



Caseine which has become insoluble in water is redis- 

 solved by alkalis, and also by solution of phosphate of soda. 



Milk-sugar, CuHaaOnHjO. — ^This substance may be ob- 

 tained from milk by coagulating the caseine and removing 

 that along with the fat, and then evaporating the residual 

 liquid (or whey) to crystallization. The crystals are decol- 

 orized by means of animal charcoal. It is distinguished 

 from cane-sugar in various ways. 



