114 PHYSIOLOGICAL CHEMISTRY. 



The so-called peptones sold commercially contain a large amount 

 of proteose. As a class the proteoses and peptones are very soluble, 

 diffusible bodies which are non-coagulable by heat. Peptones differ 

 from proteoses in being more diffusible, non-precipitable by 

 (NH 4 ) 2 SO 4 , and by their failure to give any reaction with potas- 

 sium ferrocyanide and acetic acid, potassio-mer curie iodide and 

 HC1, picric acid, and trichlor acetic acid. The so-called primary 

 proteoses are precipitated by HNO 3 and are the only members of 

 the proteose-peptone group which are so precipitated. 



Some of the more general characteristics of the proteose-peptone 

 group may be noted by making the following simple tests on a 

 proteose-peptone powder : 



1 i ) Solubility. Solubility in the ordinary solvents ( see page 23 ) . 



(2) Millon's Reaction. 



Dissolve a little of the powder in water and test the solution as 

 follows : 



(1) Precipitation by Picric Acid. To 5 c.c. of proteose-peptone 

 solution in a test-tube add picric acid until a permanent precipi- 

 tate forms. The precipitate disappears on heating and returns 

 on cooling. 



(2) Precipitation by a Mineral Acid. Try the precipitation by 

 nitric acid. 



(3) Coagulation Test. Heat a little proteose-peptone solution 

 to boiling. Does it coagulate like the other simple proteins studied ? 



SEPARATION OF PROTEOSES AND PEPTONES. 1 



Place 50 c.c. of proteose-peptone solution in an evaporating dish 

 or casserole, and half-saturate it with ammonium sulphate solution, 

 which may be accomplished by adding an equal volume of saturated 

 ammonium sulphate solution. At this point note the appearance 

 of a precipitate of the primary proteoses (protoproteose and hetero- 

 proteose). Now heat the half -saturated solution and its suspended 

 precipitate to boiling and saturate the solution with solid ammo- 

 nium sulphate. At full saturation the secondary proteoses (deu- 

 teroproteoses) are precipitated. The peptones remain in solution. 



Proceed as follows with the precipitate of proteoses : Collect 

 the sticky precipitate on a rubber-tipped stirring rod or remove it 

 by means of a watch glass to a small evaporating dish and dissolve 



1 The separation of proteoses and peptones by means of fractional precipitation 

 with ammonium sulphate does not possess the significance it once possessed 

 inasmuch as the boundary between these substances and peptides is not well 

 defined (see p. 113). 



