ON MILK AND MILK-TESTING 3I 



How should the lactometer reading be made? 



It may be conveniently made by placing the milk 

 in a cylinder, 15^ inches in diameter and 10 inches 

 high, then lowering the lactometer in the milk until 

 it floats. Let the lactometer adjust itself for about 

 half a minute before taking the reading. If more 

 than half a minute elapses before taking the read- 

 ing, cream may rise and affect the result. 



How does the temperature affect the specific gravity 

 of milk? 

 Heat causes milk to expand. A given volume of 

 cold milk will occupy more space when warmed up. 

 Hence, heat reduces the specific gravity of milk. 



By making use of the differences in specific gravity 

 of its constituents can one test milk accurately 

 for its fat content without using a chemical? 

 No, because some of the milk serum will rise 

 with the fat, even when great centrifugal force is 

 used to separate them, and the quantity of serum 

 remaining with the fat will vary with milks of dif- 

 ferent quality. 



What is a lactoscope, and how is it used? 



It is an instrument for determining approximately 

 the amount of fat in milk. It may be of some value 

 when used in connection with the lactometer. The 

 instrument consists of a graduated glass barrel with 

 a tightly fitting stopper at the bottom. The stopper 

 carries a white glass cylinder with black lines 

 thereon. The cylinder extends up into the barrel 

 a short distance. Four c. c. of milk are run into 

 the barrel and water added with thorough mixing. 



