Jan. io, 1916 
Mature Beef and Immature Veal 
681 
Control determinations. —Control determinations on leucin and 
casein and later on tyrosin were made for the purpose of ascertaining 
whether errors in procedure were responsible for the unexpected differ¬ 
ences between duplicates or whether the nature of the experimental 
material was such that interfering reactions made it practically impossible 
to obtain as close duplicates on so complex a mixture as hydrolyzed 
meat as can be obtained on certain pure amino acids. It is almost 
certain that the hydrolyzed meat contains a large variety of amino acids, 
some of which react quantitatively in five minutes; others require 
several hours; and no particular reaction time is favorable for all taken 
together. On this point the following quotations from the work of 
Van Slyke (1911) are of interest: 
Time required for different classes of amino derivatives io react quantitatively. 
Amino groups in the exposition to carboxyl, as in the natural amino-acids, react 
quantitatively in 5 minutes at 20°. The group in lysin requires one-half hour to react 
completely, lysin being the only natural amino-acid which requires more than 5 
minutes. Ammonia and methylamine require 1.5-2 hours to react quantitatively. 
Urea requires 8 hours. . . . Amino groups in purines and pyrimidines require 2-5 
hours at 20° (p. 191). 
Amino-acids which react abnormally with nitrous acid. Glycocoll and glycyl 
peptids. Glycyl-glycin, unlike the other peptids, reacts not only with its free primary 
amino nitrogen, but also as Fischer and Koelker have shown, with a part of the second¬ 
ary nitrogen in the peptid linking. This is doubtless connected with the peculiar 
behavior of glycocoll itself when treated with nitrous acid. It gives off not only 
nitrogen, but carbon dioxide and traces of some other gas, which is not absorbed by 
permanganate, indicating that decompositions deeper than the deamination occur. 
The behavior of glycocoll and glycyl peptides can be explained in three ways: . . . 
(p. 197) The gas measured is about 103 per cent of the theoretical volume of 
nitrogen . . . (p. 199). 
In the determinations on hydrolyzed meat it was observed that almost 
invariably the nitrogen gas measured would diminish a few tenths of 
a cubic centimeter in volume, if the gas were passed back into the alkaline 
permanganate pipette and allowed to remain there overnight. Whether 
this was due to the glycocoll resulting from the hydrolysis of the different 
proteins in the meat or to other disturbing factors can not be stated. It 
is probable that the secondary reactions mentioned above take place 
when hydrolyzed meat reacts with nitrous acid for 20 minutes, and they 
contribute to the difficulty of obtaining very close duplicates. 
For the control determinations on leucin a sample of Kahlbaum’s 
synthetic leucin was used. This sample was dry and contained 96.4 per 
cent of the theoretical total nitrogen obtained by the Kjeldahl method, 
indicating the presence of a non-nitrogenous impurity. Six determinations 
on N/10 leucin in 1 per cent (approximately) hydrochloric acid, made at 
various times throughout the work gave the following results: 95.4, 
95-6, 95*3, 95*3, 96.1, and 96 per cent of the theoretical total nitrogen 
present as amino nitrogen; average, 95.6 per cent. One result, 94.4 per 
cent, obtained with exhausted permanganate in the absorption pipette, 
