66 QUESTIONS AND ANSWERS 



oughly, let stand about five minutes and while it is 

 still quite warm add 17.5 c. c. of sulphuric acid. It 

 is well to add half the above amount of acid first, 

 shake thoroughly and then add the remainder and 

 shake until the casein is all dissolved. The test 

 is then completed in the same manner as for cream 

 or butter. 



It the casein in the fat test of cheese does not read- 

 ily dissolve, how may it be brought into solu- 

 tion? 



1. Let the cheese soak in the hot water in the 

 test bottle for 10 or 15 minutes before adding the 

 acid. 



2. Have the mixture of cheese and water quite 

 hot at the time of adding the acid and add the 

 acid in small quantities, shaking between each addi- 

 tion. 



3. Add an excess of acid. 



Describe the Gerber fat test for milk. 



The Gerber test depends upon the same prin- 

 ciples for separating the fat that are used in the 

 Babcock fat test. Eleven c. c. of milk, 10 c. c. of 

 sulphuric acid (specific gravity 1.825) and i c. c. 

 of amyl alcohol are used. The cork is inserted and 

 the contents of the bottle thoroughly mixed. ^ The 

 cork should then be forced in until the liquid ex- 

 tends well into the narrow graduated neck at the 

 ooposite end of the bottle. The mixture is centri- 

 fuged five minutes, the bottles resting on the 

 corked ends meanwhile. The fat column is then 

 read the same way as in the Babcock test. 



