HANDBOOK FOR BIO-CHEMICAL LABORATORY. 17 



strongly concentrated, and the peptones precipitated by the 

 addition of alcohol. The peptones thus obtained are quickly 

 dried in a desiccator connected with an air-pump. (KilJine.) 



2. The solution obtained after the digestion of fibrin with 

 pepsin as described in method 1 is first neutralized with 

 sodium hydrate, filtered through linen, and the filtrate acidi- 

 fied with acetic acid and concentrated considerably. Now 

 precipitate the albumoses by saturating with amonium sul- 

 phate, filter and press, and boil the solution with barium hy- 

 drate, and finally with barium carbonate and a large quantity 

 of water, until ammonia can no longer be detected. Eemove 

 the barium sulphate by filtration through cloth bags, and the 

 filtrate evaporated after washing the precipitate. The barium 

 peptone thus obtained is decomposed by a slight excess of 

 sulphuric acid, the barium sulphate filtered off, the solution 

 concentrated, the free acid neutralized with ammonia, and 

 after cooling add 6$ sulphuric acid (previously diluted). 

 Now precipitate with a large excess of phospho-tungstic acid, 

 filter, wash first with 6$ sulphuric acid, then with a large 

 quantity of water, after which the compound is decomposed 

 by means of barium hydrate and the excess of barium com- 

 pletely removed from the filtrate by the careful addition of 

 sulphuric acid. The solution of peptones thus obtained has a 

 distinct acid reaction, and the solid peptone may be obtained 

 therefrom by repeated precipitation and boiling with alcohol. 

 (Kilhne and Cliittenden.) 



Nuclein. 



Preparation. 1. Pure casein is dissolved in water contain- 

 ing 2 p.m. HC1 and filtered, and the filtrate digested with pep- 

 sin at 40 C. After a time a precipitate of nuclein appears; this 

 is filtered off, washed with warm water, and purified by re- 

 peated solution in a \% solution of sodium carbonate and re- 

 precipitated after filtration by the addition of dilute hydro- 



