CHAPTEE II. 

 SAHPLING fllLK. 



29. The butter fat in inilk is not in solution, like sugar 

 dissolved in water, but the minute fat globules or drops, 

 in which form it occurs, are held in suspension in the 

 milk serum (17). Being lighter than the serum, the fat 

 globules have a tendency to rise to the surface of the milk. 

 If, therefore, a sample of milk is left standing for even 

 a short time, the upper layer will contain more fat than 

 the lower portion. This fact should always be borne in 

 mind when milk is sampled. The rapidity with which 

 fat rises in milk can be easily demonstrated by leaving a 

 quantity of sweet milk undisturbed in a cylinder or a 

 milk can for a few minutes, and testing separately the 

 top, middle and bottom layer of this milk. 



The amount of mixing necessary to evenly distribute 

 the constituents of milk throughout its mass may be as- 

 certained by adding a few drops of cheese color to a 

 quart of ~ milk. The yellow streaks through the milk 

 will be noticed until it has been poured several times 

 from one vessel to another, when the milk will have a 

 uniform pale yellow color. Stiring with a stick or a 

 dipper will not produce an even mixture so quickly or 

 so completely as pouring the milk a few times from one 

 vessel to another; in sampling milk for testing it should 

 always be mixed by pouring, just before the milk is 

 measured into the bottle; if several tests are made of a 

 sample, the milk should be poured before each sampling. 



