16 HANDBOOK FOR BIO-CHEMICAL LABORATORY. 



Peptone, 



Preparation.!. Digest 2000 grms. washed fibrin, but not 

 boiled, with 5 litres of a solution of purified pepsin (see Pep- 

 sin) obtained from 600 grms. of the removed mucous mem- 

 brane of the fundus of the stomach of two pigs and contain- 

 ing 0.4$ HC1. This mixture is allowed to digest for a fort- 

 night at 37-40C., so as to insure as complete a conversion of 

 the albumoses into peptones as possible. A little thymol 

 (0.25$) may be added to prevent putrefaction. The forma- 

 tion of peptones takes place much more quickly with trypsin 

 digestion ; therefore it may be used instead of pepsin. After 

 complete digestion the solution is filtered through linen and 

 should not contain any albuminates or coagulable albumin. 

 Exactly neutralize the filtrate with soda and heat to boiling. 

 While boiling hot precipitate by saturating with ammonium 

 sulphate. Allow to cool, and separate the precipitated albu- 

 moses and the ammonium sulphate, which has crystallized 

 out, by filtration. The filtrate is again heated to boiling, 

 and made strongly alkaline with ammonia and ammonium 

 carbonate and saturated with ammonium sulphate while boil- 

 ing. Filter when cold, and boil the filtrate until the odor of 

 ammonia has entirely passed off ; now saturate again with 

 ammonium sulphate while hot, and acidify with acetic acid. 

 When cold filter and strongly concentrate the filtrate, stirring 

 constantly, and when cold decant the liquid from the salts which 

 have crystallized out. A great part of the remaining ammon- 

 ium sulphate may be removed by careful fractional precipitation 

 with alcohol ( vol.), so that at last a solution rich in peptones, 

 containing alcohol and some little ammonium sulphate, is ob- 

 tained. The alcohol is driven off by boiling the solution, 

 and the ammonium sulphate decomposed by boiling with 

 barium carbonate. The filtrate is freed from the excess of 

 barium by the careful addition of dilute sulphuric acid. This 

 last filtrate, which must not contain any sulphuric acid, is 



