40 QUESTIONS AND ANSWERS 



Why is the pipette marked 17.6? 



Because it holds 17.6 c. c. Some milk is always 

 left in the pipette, and this makes up the difference 

 between 17.6 and 17.44. 



What is meant by *' calibrating " Babcock glass- 

 ware? 



It means the determination of the correctness of 

 the graduations on the glassware. 



By what methods can glassware be calibrated? 



1. By the use of a plunger 



2. By the use of a scale. 



3. By the use of mercury. 



4. By the use of an accurate pipette or burette. 



Describe how milk-testing bottles may be calibrated 

 by the use of a plunger. 



The bottle is filled to the zero mark with some 

 liquid such as water. Any drops of the liquid 

 clinging to the walls of the neck above the zero 

 mark should be removed with a strip of blotting 

 paper. A brass plunger divided into two sections 

 connected by a small wire, and each section equal- 

 ing I c. c, is inserted in the neck of the bottle until 

 the first section is completely submerged. The 

 level of the liquid should then be exactly on the 

 5 per cent mark. 



The plunger is then inserted farther into the 

 bottle until the second section is submerged, when 

 the surface of the liquid should reach the 10 per 

 cent mark, if the bottle is correctly graduated. 

 Bottles showing* a variation of more than .2 per 

 cent should be rejected. 



