10 
BULLETIN" 202, U. S. DEPARTMENT OF AGRICULTURE. 
per cent alcohol was positive. At an acidity of 4.27 the milk coagu- 
lated with 68 per cent alcohol but the flakes were very small. In 
order to cause a coagulation with 68 per cent alcohol with medium- 
sized flakes it was necessary to increase the. acidity to 6.16. When 
potassium acid phosphate was used the results were about the same. 
These results show that it is possible by increasing the acidity of 
milk with acid phosphates to cause a coagulation with the alcohol 
test, but the acidity has to be increased to a high degree and there 
would never be enough acid phosphate in a mixed market milk for 
it to be entirely responsible for a positive alcohol test. 
Table 5. — Influence on the alcohol test of the addition of acid phosphates to milk. 
Sodium-acid phosphate. 
Potassium-acid phosphate. 
Amount 
of 5 
per cent 
solution 
of acid 
phos- 
phate 
added to 
50 c. c. of 
milk. 
Acid- 
ity. 
Alcohol test. 
Amount 
of 5 
per cent 
solution 
of acid 
phos- 
phate 
added to 
50 c. c. of 
milk. 
Acid- 
ity. 
Alcohol test. 
75 per 
cent. 
68 per 
cent. 
44 per 
cent. 
75 per 
cent. 
68 per 
cent. 
44 per 
cent. 
C.c. 

1 
2 
3 
5 
6 
2.15 
2.75 
3.33 
27 
5.50 
6.16 
i+M 
+ M 
M 
+ M 
+ VS 
+ VS 
+ M 
+VS 
C.c. 

1 
9 
3 
5 
6 
"2.'52'" 
3.13 
4.00 
5.20 
5.62 
i+M 
+ M 
+ M 
+ M 
+ VS 
+ vs 
+M 
+ VS 
1 See footnote under Table 1. 
In some cases where we increased the acidity of milk by adding 
lactic acid it was noticed that a very slight increase in acidity caused 
a positive alcohol test. At other times the acidity had to be in- 
creased to a considerable extent before the milk coagulated with 
alcohol. It occurred to us that the explanation for these differences 
might be that there were different amounts of dibasic phosphates 
present in milk and that the acid converted the dibasic phosphate into 
acid phosphate, which increased the acidity but did not cause a posi- 
tive alcohol test. In order to test this theory one experiment was 
performed, the results of which are shown in Table 6. Two flasks of 
milk were used, each containing 50 c. c. of milk. One flask was left 
normal and 0.5 per cent dibasic sodium phosphate was added to the 
other. Various amounts of N/10 lactic acid were then added to each 
flask. As may be seen from the table, when 3 c. c. of N/10 lactic 
acid was added to the normal milk, the acidity was 2.37 and the 
alcohol test was positive with both 75 per cent and 68 per cent alco- 
hol. The flakes were large and medium, respectively. The same 
amount of acid added to the milk with dibasic phosphate increased 
