10 
BULLETIN 98, U. S. DEPARTMENT OF AGRICULTURE. 
SPECIFIC GRAVITY OF MILK AND CREAM. 
Table ILT covers the specific gravity of milk and cream determined 
at 68° F. (20° C.) in terms of water at the same temperature as unity. 
Table III. — Specific gravity of milk and cream corresponding to various percentages of 
butter fat at 68° F. 
Per- 
centage 
of fat. 
Specific 
gravity. 
Per- 
! centage 
j of fat. 
Specific 
gravity. 
Per- 
centage 
of fat. 
Specific 
gravity. 
Per- 
centage 
of fat. 
Specific 
gravity. 
0.025 
1.037 
11 
1.024 
21 
1.012 
31 
1.003 
1 
1.036 
12 
1.022 
22 
1.011 
32 
1.002 
2 
1.035 
13 
1.020 
23 
1.010 
33 
1.001 
3 
1.034 
14 
1.019 
24 
1.009 
34 
1.000 
4 
1.032 
15 
1.018 
25 
1.008 
35 
.999 

1.031 
16 
1.017 
26 
1.008 
36 
.999 
6 
1.030 
17 
1.016 
27 
1.007 
37 
.998 
7 
1.029 
18 
1.015 
28 
1.006 
38 
.997 
8 
1.027 
19 
1.014 
29 
1.005 
39 
.996 
9 
1.026 
20 
1.013 
30 
1.004 
40 
.995 
10 
1.025 
FREEZING POINT OF MILK. 
The freezing point of milk depends upon its composition, but is 
always lower than that of water. The freezing point of market milk 
generally varies from 31° to 29° F. The addition of water to milk 
serves to raise the freezing point toward that of pure water, 32° F., 
while, on the other hand, the addition of fats, solids, etc., tends to 
lower the freezing point, as does also the increase in acidity. Upon 
these variations in the freezing point is based the cryoscopical method 
of determining the addition of water to milk. 
EFFFECT OF FREEZING ON MILK. 
While the action of cold on milk at a temperature above the freezing 
point has no other effect than that of varying the density and vis- 
cosity, at a temperature below the freezing point it changes the 
chemical and physical composition. 
According to Kasdorf, 1 when raw milk which was partly frozen 
at a temperature of 10.5° F., in the ordinary container, during trans- 
portation, it was found that ice first formed around the sides and at 
the bottom of the can; the central core contained most of the casein, 
sugar, and other mineral ingredients, while most of the fat was found 
in the top layer of the liquid portion. 
When milk has been frozen gradually, without agitation, and thawed 
out clots will be found floating in the liquid, composed mostly of 
albumen and fat, which may be dissolved by cooking; on the other 
hand, if the milk is preserved in a frozen condition for three or four 
weeks these clots will be very hard to dissolve, and the difficulty 
experienced in dissolving them increases as the length of time the 
Kasdorf, Otto. Eis unci Kalte in Molkereibetrieb. Leipzig, 1904, p. 20. 
