1 AIRY HUSBANDRY 
EXERCISE NO. 2 
Object: To determine the accuracy of the glassware used for making the 
Babcock lest. 
Procedure: Some state laws specify that only tested glassware is to be 
used for making the Babcock test. There are several methods 
used for determining the accuracy of the glassware. Each 
test bottle should be tested by at least two of the methods sug¬ 
gested. 
A. Calibrate each of the 10% milk test bottles with the proper 
Trowbridge calibrator, and do likewise with the 30% cream 
test bottles. Record results for the half, and for the whole 
scale. Particular care should be taken to have the neck of the 
bottles dry. Blotting paper is provided. Avoid air bubbles. 
B. Determine the accuracy of each bottle at the half and the 
whole scale by using an accurately graduated burette. Observe 
the same precautions as for A. 
C. Determine the accuracy of the whole scale by balancing the 
bottle when filled to the : ero mark with distilled water, and 
weighing again when filled to the highest graduation. 
D. Measure the length of the scale of each of the bottles and 
record as milimeters. 
E. The pipette may be calibrated by weighing a small, clean, dry 
beaker and emptying the pipette which has been filled to the 
17.6 cc. mark with distilled water at 20° C. (68° F.) into the 
beaker. The last few drops may be expelled from the pipette 
by closing the top with a finger, while the bulb is being warmed 
with the hand. Weigh the beaker with the water. The pipette 
should deliver 17.6 grams of water. 
F. Another method for determining the accuracy of the pipette is 
to empty it when filled to the 17.6 cc. mark into a graduated 
burette which has been emptied to the 20 cc. mark. The 
pipette should deliver nearly 17.6 cc. of water. 
G. The acid cylinder, for information only, should be calibrated 
by using the burette. 
See F. & W. If 307 for complete specifications of bottles and pipettes. 
Conclusions: 
Questions: (1) Describe in detail the calibration of test bottles with 
mercury. 
(2) What is the c pacity in cc. of the neck of an 8% milk test 
bottle? A 10% bottle? A 30% cream test bottle? What is 
the weight of a volune of butter fat at 140° F. in each of the 
above bottles when it just fills the neck from 0 to the highest 
graduation? 
(3) Why is the neck of a test bottle constructed so that the vol¬ 
ume represented by one per cent is equal to .2 cc? 
(4) What are the legal requirements for Babcock glassware in 
this state? 
References: F. & W. If 44, 44a, 48, 49, 50, 53-63, inclusive. Van S. pp. 
46-53; Jud. pp. 64-66; St. pp. 105-109. 
