292 PHYSIOLOGICAL CHEMISTRY 



distinguished by the concentration of ammonium sulphate neces- 

 sary to cause their precipitation and by other similar character- 

 istics. Products which are not precipitated by ammonium sul- 

 phate are said to have passed beyond the proteose state. 

 "Witte's peptone" and " Armour's peptone" are in reality mix- 

 tures of proteoses and peptones. The former is mainly proteose, 

 the latter mainly peptone. 



76. Dissolve about a half teaspoonful of "Witte's peptone" 

 in sufficient water to cause solution. Boil to coagulate any un- 

 changed protein. Filter if necessary. Saturate the hot solution 

 with ammonium sulphate. Proteoses are precipitated. Remove 

 the precipitate either by filtering, or, if it has formed in clumps, 

 by collecting with a glass rod or with a small watch glass. If the 

 latter method has been employed, filter the liquid to remove any 

 remaining proteose, and reserve the filtrate for the study of pep- 

 tones below. Press the proteose precipitate between filter papers 

 to remove as much sulphate as possible, and dissolve in a small 

 amount of water. Add solid barium carbonate in excess and 

 boil. Filter from the precipitated barium sulphate and use 

 the filtrate which contains a mixture of proteoses, for the follow- 

 ing tests: 



77. Biuret, Millon, Adamkiewicz. 



78. Precipitation with concentrated HN0 3 . If a precipitate 

 forms, it consists of the so-called primary proteoses, the only 

 members of this group which are precipitated by nitric acid. 

 Performed as a "ring test," this test is known as Heller's ring 

 test. 



79. Precipitate with picric acid. Warm. What happens? 

 Cool. 



80. Note that proteoses are not coagulated by boiling, even in 

 acid solution. 



81. The lower members of the proteose group are somewhat 

 diffusible through an animal membrane. 



Peptones. The filtrate from proteoses reserved above which 

 contains peptones, or preferably a solution of Armour's peptone 

 may be examined for peptones. After removal of proteoses by 



