312 MILK AND MILK PRODUCTS. XIV. 



filtered off, and to the filtrate more sodium sulphate solu- 

 tion, a trace of acetic acid, and solid sodium sulphate in excess 

 were added, when a suhstance, A, was precipitated; to the 

 filtrate strong acetic acid was added, when another precipitate, 

 B, was formed, and the liquid was then found to be free from 

 proteids. 



Substance A (the yield of which was about 2 % of the milk) 

 was found to contain calcium and to be soluble in water, from 

 which acetic acid reprecipitates it free from calcium and 

 insoluble in water, though soluble in alkalies. Substance B 

 was free from calcium and insoluble in water ; its amount 

 corresponded to about 0-3% of the milk. A was coagulated by 

 rennet, B w T as not. On analysis of the purified substances the 

 following figures were obtained : 



A. B. Casein (Hammarsten). 



Carbon ... 54-43 49-13 53-00 



Hydrogen ... 6'81 5-91 7'00 



Oxygen ... 22-52 27-14 22-65 



Nitrogen ... 14-82 14-13 15-70 



Sulphur ... 0-63 1-58 0-80 



Phosphorus ... 0-79 2-09 0-85 



A globulin (Engling) and a fibrin (Babcock) have also been 

 described as occurring in small quantities in milk. For all 

 ordinary purposes, however, the proteids of milk may be 

 considered as being composed mainly of casein or caseinogen 

 and lact-albumin, the amount of the latter being usually about 

 one-seventh of that of the former. 



According to recent researches" milk contains a substance 

 carnic acid, C 10 H 15 N 8 O 6 in union with phosphoric acid, the 

 amount in cows' milk being O056%, in human milk 0-124%, of 

 pfospkorcamic acid or nucleon. The compound phosphor- 

 carnic acid is said also to occur in plants, especially during 

 germination and blossoming. 



Milk Sugar Lactose or Lacto-biose occurs in the milk of 

 animals in varying quantities. It has not, with certainty, 

 been detected in plants. 



* Wittmaack and Siegfried, Jour. Chem. Soc. 1807, abst. ii. 220, and Stccklasa 

 ditto, 573. 



