STANDARDS FOR BABCOCK GLASSWARE 413 



STANDARDS FOE BABCOCK GLASSWARE 

 (Adopted by the Association of Official Agricultural Chemists of North America.) 



Sec. 1. The unit of graduation for all Babcock glassware 

 shall be the true cubic centimeter (0.998!S77 gxam 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 graduation shall be read 

 with the bottom of the meniscus in line with the mark. 



Sec. 2. The oiEcial 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 pre- 

 viously filled to zero with mercury. 



Sec. 3. Optional Methods. — The mercury and cork, alcohol 

 and burette, and alcohol and brass plunger methods may be em- 

 ployed for the rapid testing of Babcock bottles, but the accuracy 

 of all questionable bottles shall be determined by the official 

 method. 



Sec. 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.) delivered. 



Sec. 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 (0.01) percent. 



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

 (0.10) cubic centimeter, and for fractional pipettes, five-hun- 

 dredths (0.05) cubic centimeter. 



(c) For acid measures it shall not exceed two-tenths (0.20) 

 cubic centimeter. 



