6g6 
Journal of Agricultural Research 
Vol. V, No. 15 
gm. of water were added and the flask kept in a boiling-water bath for 15 minutes. 
The temperature inside the flask was 89° C. The evaporated weight of water was 
replaced. The heated skim milk was kept overnight in cold storage and digested 
the next morning with veal sample 9, after the addition of 2,000 gms. of trypsin 2, 
1 liter of 1 per cent sodium carbonate, and 200 c. c. of water; total volume, 2,098 c. c. 
The neutralization of the 100 c. c. portions of digestion fluid were made, as usual, 
with 24.5 c. c. of NI0.4 sulphuric acid, followed by heating to a boil. Extractive 
nitrogen was determined in a similar portion of skim-milk sample 2 in 0.5 per cent 
sodium carbonate; 27.5 and 29 c. c. of NI0.4 sulphuric acid were used for the pre- 
Fig. 2.—Experiment 20. Curve showing the quantity (in cubic centimeters) of iV/5 nitrogen in 100 c. c. 
of digestion fluid, equivalent to approximately 5 gm. of meat; used 100 gm. of meat, 2,000 c. c. of 0.5 per 
cent sodium carbonate, and 2,000 gm. of trypsin 1. 
cipitation of 30 gms. of skim-milk sample 2 contained in 100 c. c. of 0.5 per cent 
sodium carbonate. 
In the two following diagrams (figs. 2 and 3) the data of experiments 20 and 28 
are graphically represented. 
third method: measuring the rate or liberation op free amino groups 
These determinations were made on the same digestion mixtures used in experi¬ 
ments 26 to 34. Portions of 100 c. c. of the supernatant digestion fluid were removed 
for the determination of the nitrogen present as alkali proteinate, proteoses, peptones, 
etc., as already described. In addition, 10 c. c. portions of the digestion fluid were 
transferred to the Van Slyke amino-nitrogen apparatus, and free amino nitrogen was 
determined by the method already described on p. 680. 
In this method, as in the previous ones, particular care was taken to check the 
action of the trypsin on the minute. The digestion mixtures in the 40° C. water bath 
were mixed 15 minutes before the time intended for the determination. The undi¬ 
gested meat particles were allowed to settle for 10 minutes. During this time the 
amino-nitrogen apparatus was made ready for the determination. Two or three 
minutes before the digestion period was to be brought to a close, 10 c. c. of the super¬ 
natant digestion fluid were transferred to the apparatus, and exactly at the expiration 
of the digestion period the digestion fluid was allowed to enter the reaction chamber 
of the apparatus. This brought the digestion to a close. 
The results obtained are summarized in Table XII. Amino nitrogen in the extrac¬ 
tives was determined in portions of the same filtrates that were used for total extractive- 
