42 QUESTIONS AND ANSWERS 



How may mercury be used to calibrate the testing 

 bottles? 



From a correctly graduated burette run 2 c. c. of 

 mercury into the clean and dry test bottle. Then 

 push a close-fitting stopper into the neck of the 

 bottle level with the highest graduation. When 

 the bottle is turned upside down the mercury should 

 just fill the graduated portion of the neck. The 

 mercury may be transferred from one bottle to an- 

 other without loss by connecting the necks with a 

 piece of closely fitting rubber tubing. In this 

 manner several bottles may be tested with the 

 same mercury. 



How may the bottles be calibrated by use of a 

 burette? 



Fill the bottles exactly to the zero mark with a 

 liquid. Then run in from the burette liquid to fill 

 the graduated part of the neck. Each two-tenths 

 of a c. c. taken from the burette should equal i per 

 cent in the neck of the bottle. By this means each 

 per cent of space in the neck may be readily cali- 

 brated. 



How may the pipette be calibrated? 



By closing the tip and running in 17.6 c. c. of 

 liquid from a correctly graduated burette. The 

 surface of the liquid should then be level with the 

 mark on the stem. Or one may accurately balance 

 a small vessel on scales. Place 18 grams on the 

 opposite side of the scales. Then fill the pipette 

 to the mark with milk having a Quevenne lac- 

 tometer reading of 32. Allow the milk to run into 

 the vessel, blowing the drop from the tip of the 



