8 
BULLETIN 1460, U. S. DEPARTMENT OF AGRICULTURE 
Table 2. — Sulphuric acid 1 losses due to heating and to oxidation of ivheat 
samples 
Treat- 
ment 
No. 
Treatment 
Protein 
Intensity of 
heat 
Acid 
used 
Acid 
lost by 
heating 
Acid lost 
by oxi- 
dation 
Total 
loss due 
to heat 
and oxi- 
dation 
1 
Acid only starting. . _•_ 
Per cent 
No heat 
Low 
High 
Medium 
do 
do 
do 
do 
do.. 
do 
do 
do 
do 
do 
do 
do 
do 
do 
.....do 
do....... 
C.c. 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
20 
25 
25 
25 
C.c. 
C.c. 
C.c. 
2 
10 gr. K2SO4 and 0.7 gr. HgO 
2.0 
3.5 
2.4 
2.3 
2.5 
2.5 
2.4 
2.4 
2.4 
2.4 
2.4 
2.4 
2.4 
2.4 
2.4 
2.4 
3.0 
3.0 
3.0 
3 
do 
do 
4 
5 
10 gr. Na 2 504 and 0.7 gr. HgO ... 
10 gr. Na 2 S0 4 and 0.2 gr. CuS0 4 . . - 
7 gr. Na 2 S0 4 and 0.1 gr. CuS0 4 
and 0.5 gr. HgS0 4 . 
Treatment 4: 1 gr. 11998 
10.66 
12.88 
15.45 
12.77 
14.53 
10.20 
8.26 
8.09 
17.73 
18.07 
12.88 
14.53 
8.26 
6 
7 
8 
3.8 
3.4 
3.4 
3.4 
3.1 
4.5 
3.6 
3.7 
3.5 
3.4 
6.7 
7.0 
6.6 
6 2 
9 
Treatment 4: 1 gr. 12002 
5 8 
10 
Treatment 4: lgr. 12003 . . 
5.8 
11 
Treatment 4: 1 gr. 12005.. 
5.8 
12 
Treatment 4: 1 gr. 12006 
5.5 
13 
Treatment 4: 1 gr. 12007 
7.9 
14 
Treatment 4: lgr. 12376 
6.0 
15 
Treatment 4: 1 gr. 12868 
6. 1 
16 
Treatment 4: 1 gr. 12878 
5.9 
17 
Treatment 4: 1 gr. 12883 
5.8 
18 
Treatment 4: 2 gr. 12002 
9.7 
19 
20 
Treatment 4: 2 gr. 12006. . 
Treatment 4: 2 gr. 12376... 
10.0 
9.6 
1 Specific gravity of acid, 1.82 at 25° C. 
Average acid lost from heat and oxidation of a 1-gram sample with 20 cubic centimeters of acid, 6.0 cubic 
centimeters, of a 2-gram sample with 25 cubic centimeters of acid, 9.8 cubic centimeters. 
Knowing the acid losses as given, the optimum quantity of acid 
to use can then be calculated if further information is at hand re- 
garding the acid necessary to hold the ammonia nitrogen split off 
from the protein molecule. To determine this, a portion of the work 
of Paul and Berry 8 was repeated and the data are given in Table 3. 
Table 3. — Sulphuric acid necessary to hold the ammonia present during' the 
digestion period 
Concentrated sulphuric acid in flask 
Protein 
present 
Differ- 
ence 
sebies I 
(NH 4 ) 2 S0 4 as protein added 
30 c. c. H 2 S0 4 , 10 gr. K 2 80 4 , 0.7 gr. yellow HgO. 
25 c. c. H 2 S0 4 , 10 gr. K 2 S0 4 , 0.7 gr. yellow HgO. 
20 c. c. H 2 S0 4 , 10 gr. K 2 S0 4 , 0.7 gr. yellow HgO . 
15c. c. H 2 S0 4 , 10 gr. K 2 S0 4 , 0.7 gr. yellow HgO. 
10 c. c. H 2 S0 4 , 10 gr. K 2 S0 4 , 0.7 gr . yellow HgO . 
5 c. c. H 2 S0 4 , 10 gr. K 2 S0 4 , 0.7 gr. yellow HgO.. 
SERIES II 
(NH 4 ) 2 S0 4 as protein added 
30 c. c. H 2 S0 4 , 10 gr. Na 2 S0 4 , 0.7 gr. yellow HgO 
25 c. c. H 2 S0 4 , 10 gr. Na 2 S0 4 , 0.7 gr. yellow HgO 
20 c. c. H 2 S0 4 , 10 gr. Na 2 S0 4 , 0.7 gr. yellow HgO 
15 c. c. H 2 S0 4 , 10 gr. Na 2 S0 4 , 0.7 gr. yellow HgO 
10 c. c. H 2 S0 4 , 10 gr. Na 2 S0 4 , 0.7 gr. yellow HgO 
5 c. c. H 2 S0 4 , 10 gr. Na 2 S0 4 , 0.7 gr. yellow HgO. 
Per cent 
13.57 
13.62 
13.57 
13.57 
13.57 
13.62 
3.42 
13.57 
13.57 
13.57 
13.57 
13.57 
13.62 
3.76 
Per cent 
0.05 
.05 
10.15 
.05 
9.81 
This experiment was made with both sodium and potassium sul- 
phates as catalytic agents, as it was felt by some of the collaborating 
laboratory personnel that sodium sulphate induced greater acid losses 
8 Paul, A. E. and Berry, E. H. the kjeldahl nitrogen method and its modifica- 
tions. Jour. Assn. Off. Agr. Chem., vol. 5, No. 1, pp. 108-32. 1921. 
