Jan. 7. 1918 Effect of Time of Digestion on Hydrolysis of Casein 



from 12 to 15 hours with 20 per cent hydrochloric acid gives results for 

 the amino-acid groups that are comparable with those obtained by 

 Van Slyke upon casein alone. 



(2) A digestion period of more than 15 hours with 20 per cent hydro- 

 chloric acid on a casein-starch mixture brings about a redistribution of 

 the nitrogen contained in the histidin and cystin groups. 



(3) The insoluble residue obtained from a casein-starch digestion 

 after being thoroughly washed contains nitrogen, which is not seriously 

 affected when distilled with calcium-hydrate suspension, very small 

 amounts being split off as ammonia or remaining in the filtrate. This 

 indicates that the nitrogen is in an inert form and its estimation should 

 not be included in the humin determination. 



