84 BUTTER-MAKING. 
less than .3% acid, while others will not coagulate until more 
than .3% acid has developed. 
In practice the temperature (120° F.) is not always considered. 
A small portion of the sample to be tested is put into a tin cup. 
The cup containing the milk is put into hot water or over a jet 
of steam. When hot its characteristics are noticed. 
5. Use of Babcock Test and Lactometer.—These tests are 
of special value in detecting watered or skimmed milk. When- 
Fic. 28.—Acid carboy trunnion. Fic. 29.—Acid hydrometer. 
ever a sample of milk appears watery or blue, it is fair to presume 
that water has been added. The test for specific gravity and 
the test for fat can then be applied to such samples of milk. 
As a rule composite samples are taken daily at creameries, and 
the patrons paid according to the fat delivered. For this 
reason water adulteration is not very common at creameries, 
but is practiced to a greater extent in the milk-supplies of 
cities. The use of the lactometer in connection with the Bab- 
cock test has already been referred to under the heading of 
“Specific Gravity of Milk.” 
