DAIRY HUSBANDRY 
9 
EXERCISE NO. 4 
Object: To determine the strength of the sulfuric acid used for the Babcock 
test. 
Procedure: Sulfuric acid for the Babcock test should have a specific 
gravity of 1.82-1.83 or should be 90-92% pure. 
A. The specific gravity may be determined by using the Westphal 
balance as follows: The balance should be leveled carefully. 
The screw on the beam should be adjusted so that it balances 
exactly with the plunger suspended in the air. The glass 
cylinder should be filled with acid at 15° C. (59° F.) and placed 
so that the plunger will just be submerged. Proper weights 
are thus placed on the beam until it again balances. Take the 
reading. 
B. Place acid at a temperature of 15° C. (59° F.) in a tall glass 
cylinder and insert acid hydrometer. Read the specific gravity 
direct. 
Note: Great care should be taken to avoid having acid come 
in contact with metal or wood. 
Observations: 
Sample 
Temperature 
Sp. gr. 
Sp. gr. 
Westphal 
Hydrometer 
1 
2 
Conclusions: 
Questions: (1) What effect has temperature on the specific gravity of 
sulfuric acid? 
(2) What happens if a bottle of sulphuric acid remains unstop- 
per^d? 
(3) Give 3 reasons why sulfuric acid is used when making a Bab¬ 
cock test for fat in milk. 
(4) Describe another method of determining the specific gravity 
of sulphuric acid. 
References: F. & W. f 72-78, inclusive; Van S. pp. 43-46; Jud. 62; St. 
P. 115. 
