398 
Journal of Agricultural Research 
Vol. XXX, No. 5 
Table III.— Loss of nitrogen and carbon during the drying of cow’s feces-and- 
urine mixture 
Carbon lost per day 
Experiment and period 
Dry matter 
per day 
Nitrogen 
lost per 
day 
Total 
Combined 
with nitro¬ 
gen com¬ 
puted from 
N lost) 
Not com¬ 
bined with 
nitrogen 
221f: 
Grams 
Grams 
Grams 
Grams 
Grams 
874 I_ 
2,225.8 
78.3 
71.9 
33.6 
38.3 
874 II_ 
1,516.0 
50.3 
58.8 
21.6 
37.2 
887 I_ 
1,887.4 
82.0 
70.7 
35.2 
35.5 
887 II_ 
1,296. 5 
59.2 
48.5 
25.4 
23.1 
886 I_ 
3,178.8 
83.9 
119.6 
36.0 
83.6 
886 II_ 
2,739. 8 
96.8 
124.7 
41.5 
83.2 
221g: 
887 I_ 
2,793.1 
57.7 
108.3 
32.5 
75.8 
887 II_ 
1,405.3 
58.5 
82.2 
25.1 
57.1 
887 III_ 
2,072.2 
61.4 
79.3 
26.3 
53.0 
887 IV_ 
2,924.1 
87.3 
83.5 
37.5 
46.0 
To diminish this possibility of error 
in the carbon balance, in those cow 
experiments in which the carbon was 
not determined in the fresh feces-and- 
urine mixture, the loss of carbon on 
drying, per gram of nitrogen lost, was 
computed from the average of the data 
available, this average being 1.15 gm. 
and the correction for carbon lost on 
drying was computed by the use of this 
facfor. That this correction is not en¬ 
tirely satisfactory is realized, since the 
loss of carbon does not in all cases follow 
exactly the loss of nitrogen, but it was 
considered, under the conditions, as the 
best possible way of correcting these 
earlier results which were obtained 
from the air-dried material. 
LOSS OF ENERGY IN AIR-DRYING FECES- 
AND-URINE MIXTURE 
A loss of nitrogen and carbon on 
drying does not mean a loss of only 
these elements, but it also represents a 
certain loss of potential energy. While 
the original fresh feces-and-urine mix¬ 
ture might have contained some carbon 
as free C0 2 , the quantity so contained, 
in view of its solubility, could be only a 
very small fraction of the total quantity 
lost during the drying. Some of this 
loss no doubt came from the decomposi¬ 
tion of urea, and this portion has been 
estimated in the experiments from the 
nitrogen lost. The remainder has been 
assumed, in the absence of definite 
knowledge, to be a result of carbohy¬ 
drate fermentation, since the conditions 
of the drying are regarded as favorable 
for such a process. On this basis the 
energy lost on drying has been com¬ 
puted by using Rubner’s factor, 5.45 
for loss in Calories per gram of nitrogen 
lost, and the factor 9.4 for computing 
Calories per gram of carbon lost in 
excess of that required to satisfy the 
nitrogen lost, the latter factor repre¬ 
senting the energy per gram of carbon 
in starch. 
Although the above computation is 
not without logical justification, one 
must admit the possibility of consid¬ 
erable error in this correction, in view 
of our imperfect knowledge as to the 
nature and extent of the losses. Since 
it is impracticable directly to deter¬ 
mine the energy in the fresh feces-and- 
urine mixture, the drying process may 
be, therefore, a source of serious error 
in the computation of the heat pro¬ 
duction. 
To illustrate the extent to which the 
above considerations, as to losses and 
corrections may affect the computed 
heat production Table IV has been 
compiled, the data in the three methods 
of computation being derived from the 
data of experiments 22 If and 22 lg. 
In all three cases the nitrogen was 
determined in the fresh substance, and 
energy in air-dry substance. In 
Method I carbon was determined in the 
air-dry material. Corrections for car¬ 
bon and energy were computed from the 
nitrogen lost, calculated as urea. In 
Method II carbon was determined in 
the fresh material, corrections for 
energy being computed as in Method 
I. In Method III the carbon was 
determined in the fresh material and 
the corrections for energy were com¬ 
puted as in Method I, with an addi¬ 
tional correction for carbon lost in ex¬ 
cess of that required to combine with 
the nitrogen to form urea (using the 
factors 5.45 per gram nitrogen and 9.4 
per gram carbon). 
