96 



CHEMISTRY OF THE PROTEIDS 



CHAP. 



If the reaction between nitrous acid and albuminous matter takes 

 place according to the equation given above, then the amid-nitrogen 

 ought to be completely removed from the albumin-molecule. Levites 

 has examined desamino-albumin prepared from egg-white, freed from 

 globulins and ovomucoid ; desamino-casein (Hammarsten-Griibler) and 

 desamino-glutin from purified gelatine. 



Desamino - albumin and desamino - casein gave both the biuret- 

 reaction and the reaction of Millon, while desamino-glutin gave a 

 distinct biuret-reaction. 



In the following table the author has compiled "mean readings" 

 from the figures given by Levites : 



This table shows that the amid-nitrogen remains nearly unaltered 

 after treatment with nitrous acid, if it is not even increased in 

 amount, while the total-nitrogen is considerably diminished. Accord- 

 ing to Levites the occurrence of CONH 2 - radicals in the albumin- 

 molecule is therefore not yet proved, nor can the biuret-reaction be 

 said to depend on these CONH 2 -groups, especially as the pepsin-glutin- 

 peptones of Scheermesser contain no trace of amid-nitrogen. 



(g) Disintegration of Albumins with Bromine 



Hlasiwetz and Habermann * have heated eggwhite under pressure 

 with an excess of bromine in watery solution, and they obtained from 

 100 grammes eggwhite (see also Chapter VII., p. 230) : 



29*9 grammes Bromoform. 



22 Brom-acetic acid. 



12 Oxalic acid. 



1 H. Hlasiwetz and J. Habermann, Liebig's Ann. 159. 304 (1871). 



