TESTING THE FARM HERD 71 



or two c.c. of acid at first and gently shake. Do not 

 hurry the process, but give the ether plenty of time 

 to evaporate. The acid should be added in small por- 

 tions until the required amount has been added. 



e. The reading must be corrected to allow for the 

 ether added. Compare the result with the test of the 

 original milk. 



Note: This exercise requires extreme care and skill in its 

 manipulation if accurate results are to be obtained. 



X. To Determine the Calibration of Glassware Used in 

 Connection with Babcock Test 



a. Fill a 10 per cent milk test bottle to the zero 

 mark with water. With a strip of blotting paper, 

 carefully absorb the water adhering to the sides of 

 the neck of the bottle. Observe particularly that the 

 height of the water is exactly at the zero mark. 



b. With a graduated burette, drop 2 c.c. of water 

 into the bottle. Observe the height to which it fills 

 the bottle. Test bottles are so made that it takes 2 c.c. 

 to fill 10 per cent on the neck of the bottle, i. e., 

 2 c.c. of water or alcohol should exactly fill the space 

 from to the 10 per cent mark. 



c. Prepare another bottle as under "a." Insert 

 a Trowbridge plunger and observe the height to which 

 it raises the water. 



d. Cream bottles can likewise be tested. 



e. Into a beaker place the contents of a 17.6 c.c. 

 pipette of milk. If the pipette is accurate the amount 

 of milk delivered will weigh 18 grams. 



Note: In calibrating glassware many prefer to use colored 

 denatured alcohol. The liquid should be at room temperature. 

 It is not advisable to hold the bottles In the hand, as the 

 heat of the hand may change the temperature and make the 

 results inaccurate. 



