392 THE AMIDE NITROGEN OF PROTEIDS. 



percentage figures as constant, and in particular he char- 

 acterizes the amount of amide nitrogen split off "as a 

 sharply determinable and for each proteid a very characteristic 

 quantity." 



To settle this question fully, the writer has performed a 

 series of investigations in which proteids purified with the 

 utmost care were boiled for various periods with hydrochloric 

 and sulphuric acid of various strengths.* The figures giving 

 the results, and set forth in the accompanying table seem to 

 show that the concentration of the acid used, as well as the 

 duration of boiling, exert a decided influence on the distribu- 

 tion of the nitrogen between the different classes of cleavage 

 products. This was shown most clearly when the proteids 

 were treated with sulphuric acid, evidencing the relation 

 |?etween the strength of the reagent and the period of action 

 on the one hand, and on the other the amount of amide 

 nitrogen split off. With hydrochloric acid also results similar 

 in kind were obtained. 



In these investigations the amide nitrogen alone has been 

 determined. Yet since they show that the figures obtained 

 are dependent upon the conditions of experiment, it is imme- 

 diately evident that every increase or diminution in these 

 figures must be accompanied by a corresponding diminution 

 or increase in the amount of diamino or monoamino nitrogen, 

 or, perhaps, in both. The results obtainable for the mono- 

 amino and diamino nitrogen must necessarily be subject to 

 considerable variations, as well as those for the amide 

 nitrogen. 



* The method of these determinations was essentially the same as that of 

 Hausmann. 



