32 



INTRODUCTORY — THE COXSTITUENTS OF MTLK. 



basic ones. On hydrolysis it ultimately yields, according to 

 Fischer and others, especially Osborne and Greed, the following 

 (the estimations of leucine, glutamic acid, tyrosine, lysme, 

 arginine, and histidine are probably nearly correct ; the other 

 figures probably low) : — 



Levites has also shown that casein contains 0-93 per cent, of 

 nitrogen removed by the action of nitrous acid — i.e., as free 

 NH2 group — this compound, however, yielded as much nitrogen 

 as ammonia (1-67 per cent.) as the original casein. 



When dissolved in dilute alkali it has a Isevo-rotatory action on 



polarised light. J. H. Long gives the specific rotation of casein 



when 5 grammes are dissolved in 100 c.c. of water with the 



N . . 



number of c.c. of — :- alkali given as follows : — 



NaOH, 



KOH, 

 LiOH, 



NHjOH, . 



It is completely precipitated from milk by copper sulphate ; 

 if the solution be neutral, a definite compound containing about 

 1 per cent, of copper is obtained ; basic compounds are probably 

 obtained if the solution be alkaUne. Mercury salts precipitate 

 casein completely, even in acid solution ; it is also precipitated 

 by meta-phosphoric acid. Casein has probably a higher mole- 

 cular weight than the other proteins existing in milk. 



