62 A DAIRY LABORATORY GUIDE 



EXPLANATION OF EXERCISE X 



In testing butter by the Babcock method, the 

 practice is sometimes followed of melting the 

 butter and then putting it into the test bottle 

 by means of the pipette. It is possible to do 

 this sometimes and get accurate results, but 

 the tendency for fat and water to separate 

 makes it difficult to get accurate tests. 



Division &of experiment 2 illustrates how readily 

 the fat and water separate. In drawing off 

 the fat for this experiment, keep the point of 

 the pipette at the surface of the fat. 



Carbon dioxide acts toward an alkali like an 

 acid. We are told that some of the acidity 

 of the milk is due to the presence of CO2. 

 In experiment 4, pouring the milk back and 

 forth from one vessel to another tends to mix 

 the CO2 of the air with the milk. Heat will 

 expel the CO2, and so after boiling the milk 

 the acid test would be lower than it would 

 be before boiling. This experiment also 

 shows that milk will take up gases. 



