50 QUESTIONS AND ANSWERS 



The disadvantages are: 



1. Excessive amounts are sometimes necessary 

 in hot weather to preserve the milk. 



2. Then it interferes with the acid dissolving the 

 casein and a clear test is not secured. 



3. High acidity of the milk reduces its preserva- 

 tive qualities. 



4. Samples containing it may form a tough skin 

 over the surface, especially in the light, more read- 

 ily than with other preservatives. 



How should the composite bottle be handled while 

 adding milk? 

 Each time a bottle is taken from its place it 

 should be held in an upright position until it has 

 been quickly whirled in a circle. This mixes the 

 fat with the remainder of the sample and prevents 

 it from becoming attached to the sides of the bottle 

 and drying. The next portion of milk may then 

 be added and the Sample shaken once more to dis- 

 tribute the fresh milk and the preservative evenly. 



How often should composite samples be shaken, 

 and how long may they be kept before testing? 

 Composite samples should be shaken once a day 

 whether fresh milk is added or not. They should 

 be tested every ten days or two weeks at the 

 longest. 



What special precautions are necessary in the test- 

 ing of composite samples? 

 I. Be certain that any cream that may have be- 

 come attached to the sides of the container is re- 

 moved. 



