on this particular phase of the subject a matter of considerable 
importance. During our recent investigations of the Washington 
milk supply we have made the following observations on the coagu- 
lation of slightly sour milk at or below boiling: 
No. of 
obser- 
va- 
tion. 
Date. 
No. of sample. 
Acidity of 
sample 
(per cent) . 
Temper- 
ature 
(°C.). 
Time of 
exposure 
(min- 
utes) . 
Curdled 
(+) or 
not cur- 
dled (— ). 
1 
Sept. 27, 1907 
do » 
0.567 
65 
1 
+ 
2 
do 
.342 
66 
5 
3 
do.. 
. .do 
.342 
78.5 
2 
+ 
4 
.do... 
.252 
100 
1 
5 
Sept. 25, 1907 
do 
do 
.306 
75 
3 
+ 
6 
41 C 
.441 
66 
1 
+ 
7 
do 
36 C 
.711 
65 
(a) 
1 
+ 
8 
do 
35 C 
.594 
65 
1 + 
9 
Sept. 24, 1907 
do 
26£ C 
.513 
65 
2 
+ 
10 
27 C 
.450 
65 
1* 
5 
+ 
11 
do 
29 C 
.351 
65 
65 
+ 
12 
do 
31 C 
.243 
10 
13 
do 
31 C . 
.243 
72-74 
10 
14 
do 
Hutson 
. 576 
‘65 
2 
+ 
15 
Sept. 21, 1907 
do 
do 
.252 
70 
5 
16 
do ... . 
.288 
70 
5 
17 
do 
. . . . do . . . . 
.315 
70 
5 
18 
do . . . 
.do... 
.315 
70 
10 
+ 
19 
Sept. 20, 1907 
do 
10 c 
.531 
65-67 
2 
+ 
20 
12 C 
.351 
65—67 
2 
+ 
21 
do 
15 C 
.225 
65-67 
65 
2 
+ 
22 
Sept. 18, 1907 
do . 
Hutson. 
.387 
5 
+ 
23 
. . do . „ . 
.306 
65 
5 
24 
do 
do 
.315 
65 
5 
25 
do 
do 
.234 
65 
5 
26 
do 
do 
.261 
65-74 
65 
5 
27 
do 
.do 
.198 
5 
28 
....do... 
do 
.180 
65 
5 
29 
July 26,1907 
July 24,1907 
July 25,1907 
July 26,1907 
do 
. 554 
60 
2 
+ 
30 
do : 
.243 
100 
1 
31 
9 B and 11 B 
.478 
60 
5 
+ 
32 
29 B 
.351 
65 
5 
+ 
a Immediately. 
It will be seen from our results that of those samples of milk which 
coagulated on heating, sample 15 C. contained the smallest amount of 
acid at the time of coagulation, viz, 0.225 per cent. (See observa- 
tion 21.) This sample curdled in two minutes at 65°-67° C. Other 
samples containing from 0.306 to 0.315 per cent of acid curdled at 
temperatures varying from 65°-78.5° C., in from two to ten minutes, 
and as a general rule those milks are most easily coagulated by heat 
which have the highest acidity. On the other hand, while one of the 
samples having an acidity of only 0.225 per cent curdled at 65°-67° C., 
in two minutes, another sample containing 0.243 per cent of acid did 
not curdle even on boiling. Thorner (15) found the acidity necessary 
