278 MODERN METHODS OF TESTING MILK 



STANDARD OF ACCURACY FOR BABCOCK 

 GLASSWARE AND RULES FOR TESTING 



SECTION *. The unit of graduation for all Babcock 

 glassware shall be the true cubic centimeter (.998877 

 gram of water at 4 degrees C). 



(a) With bottles, the capacity of each per cent, on 

 the scale shall be two-tenths (0.20) cubic centimeter. 



(b) With pipettes and acid measures, the delivery 

 shall be the intent of the graduation, and the gradua- 

 tion shall be read with the bottom of the meniscus in 

 line with the mark. 



SECTION 2 The official method for testing bottles 

 shall be calibration with mercury (13.5471 grams of 

 clean, dry mercury at 20 degrees C., carefully weighed 

 on analytical balances, to be equal to 5 per cent, on the 

 Babcock scale), the bottles being previously filled to 

 zero with mercury. 



SECTION 3 Optional methods The mercury and 

 cork, alcohol and burette, and alcohol and brass- 

 plunger methods may be employed for the rapid testing 

 of Babcock bottles, but the accuracy of all questionable 

 bottles shall be determined by the official method. 



SECTION 4 The official method for testing pipettes 

 and acid-measures shall be calibration by measuring in 

 a burette the quantity of water (at 20 degrees C.) de- 

 livered. 



SECTION 5 The limits of error (a) For Babcock 

 bottles shall be the smallest graduation on the scale, 

 but in no case shall it exceed five-tenths (0.50) per 

 cent., or for skim-milk bottles one-hundredth (o.oi) 

 per cent. 



(b) For full-quantity pipettes, it shall not exceed 

 one-tenth (o.io) cubic centimeter, and for fractional 

 pipettes, five-hundredths (0.05) cubic centimeter. 



(c) For acid-measures it shall not exceed two-tenths 

 (0.20) cubic centimeter. 





