50 THE PROTEINS. 



gives no reaction for sulphates with barium chlorid. If 

 the water is warm some antiseptic like thymol or chloro- 

 form must be used. The albumose reactions can be made 

 with this solution from the dialyzer. 



If the dry proteoses are desired concentrate the solu- 

 tion to a small bulk and precipitate them with an excess 

 of alcohol, washing with the same after filtration. Dry 

 in a vacuum desiccator over sulphuric acid. 



116. Dissolve some of the proteose in water and show that 

 it is precipitated by potassium ferrocyanid in a solution acidified 

 with acetic acid, avoiding an excess of the former. 



117. Show that a solution of proteose in water is not coagu- 

 lated by neutralizing nor boiling. Nitric acid gives a white pre- 

 cipitate which dissolves on heating and reappears on cooling. (Dis- 

 tinction from albumin and albuminates.) 



118. PREPARATION OF PEPTONE. Digest blood-fibrin in a 

 neutral solution with a watery extract from a chopped pancreatic 

 gland at about body-temperature. If it is allowed to stand many 

 hours, add a few crystals of thymol to prevent putrefaction. 

 Boil after solution has taken place, filter, concentrate by boiling, 

 and saturate while boiling with ammonium sulphate to precipitate 

 the albumoses. Filter these out, first by muslin, then by filter- 

 paper. The solution may be used for testing or the ammonium 

 sulphate may be removed largely by evaporation and crystalliza- 

 tion. The remainder can be removed by adding first barium 

 hydrate, then barium carbonate, and boiling, until a portion of 

 the filtrate gives no precipitate with barium chlorid. 



119. Commercial peptone may be used for testing. 

 Test the solution of peptones by adding first sodium hy- 

 drate, then not more than two or three drops of copper sul- 

 phate (biuret test). A red or pink color is produced, 

 which is characteristic of the peptones. If too much of 

 the copper solution is added, the color is bluish. 



120. Place some of the solution in a dialyzer and 

 leave it an hour, then test the solution outside for the 



