100 Milk and Its Products 



any variation in the size of the spaces such bottles 

 should be discarded. Bottles inaccurate in this 

 respect are seldom met with now. When the test 

 was first introduced they were of frequent occur- 

 rence. Bottles may be readily tested with a pipette 

 of 2 c. c.* capacity. Fill the bottle carefully with 

 water to the point, wipe out the neck carefulh', 

 and drop in exactly 2 c. c. of water. It should 

 just fill the neck to the top of the graduation. 

 If delicate balances are at hand, the bottle may be 

 weighed full of distilled or clean rain water to the 

 point, and then again filled to the 10 point. 

 The difference in weight should be exactly 2 grams. 

 The calibration will be still more accurate if mer- 

 cury instead of water is used ; 2 c. c. of mercury 

 may be measured out, or, what is still better, 

 weighed. The specific gravity of mercury is 13.59 ; 

 two c. c. will, therefore, weigh 27.18 grams. This 

 weighed or measured quantity of mercury is intro- 

 duced into a dry bottle, a close-fitting plug is then 

 inserted into the neck of the bottle exactly to the 

 top of the graduation, 'the bottle is then inverted ; 

 the mercury should exactly fill the graduated space. 

 The same portion of mercury can then be used to 

 test another bottle, and with care to have the 

 bottles dry, and to see that all of the mercury is 

 transferred each time, a large number of bottles can 

 be easily and quickly calibrated. 



The pipettes are best tested by weighing a 

 pipette full of either water or mercury ; the former 



* Cubic centimeter. See metric system, in Appendix. 



