556 Non-Protein Nitrogen of Wheat Flour 
times as much nitrogen in the acid amide form. The figures for 
amino nitrogen vary widely from those obtained by Swanson 
and Tague who determined amino nitrogen in a patent flour 
using Sdrensen’s formol titration method and report about nine 
times as much as is found in these experiments. They used 
flour extracts without attempting to remove the proteins. Van 
Slyke micro determinations were made directly on some flour A 
extract in this laboratory in order to obtain a more satisfactory 
comparison with their method. The presence of the proteins 
made it impossible to take an adequate concentrated sample so 
that determinations had to be made using 5 cc. of the extract, 
corresponding to 0.25 gm. of flour. This, according to the 
method used by Swanson and Tague, should give about 0.1 ce. of 
nitrogen gas which may be easily measured in the micro-appa- 
ratus. In no case, however, could more than 0.02 cc. be ob- . 
tained, while the average of four determinations was about 0.01 
ec., which is too small an amount to be considered for the pur- 
poses of a satisfactory determination, although quite in accord- 
ance with the findings using the Van Slyke method on the con- 
centrated extract from which the proteins had previously been 
precipitated with copper; 7.e., Solution X. | 
Table II shows an increase in ammonia and amino nitrogen 
in Solution X after prolonged hydrolysis with strong acid. The 
increase, however, is not great enough to indicate the presence of 
any considerable amount of protein. It suggests, however, that 
there is some nitrogen in the form of peptides which escapes pre- 
cipitation by the copper method, although it does not preclude the 
possibility that traces of protein may still be present also. Hart 
and Bentley,® studying the non-protein nitrogen of some feeding- 
stuffs, found that after treatment with Stutzer’s reagent some 
nitrogen of the nature of peptide linkings remained in solution. 
The same seems to be true when Osborne’s procedure is followed, 
although it is probable that the precipitation of the true proteins 
is practically complete if the proper manipulation is followed. 
4 Swanson, C. O., and Tague, E. L., J. Am. Chem. Soc., 1916, xxxviil, 
1098. 
’ Hart, E. B., and Bentley, W. H., J. Biol. Chem., 1915, xxii, 477. 
