48 Testing Milk and Its Products. 



a diameter of at least one-eighth of an inch, as is gener- 

 ally the case. We have used or inspected some half a 

 dozen other devices placed on 

 the market by various deal- 

 ers for delivering the acid, 

 but cannot recommend them 

 for use in factories or outside 

 of chemical laboratories. 



52. Instead of measuring out the 

 acid, Bartlett 1 has suggested add- 

 ing 20 cc. directly to the milk in 

 the test bottles, till the mixture 

 rises to a mark on the body of the 

 bottle at the point where this will 

 hold 37.5 cc., i. e., the total volume 

 of milk and add (83). This method 

 of adding the acid is in the line of 

 simplicity, but has not become gen- 

 erally adopted. If the method is 



FIG. 18. Swedish acid-bottle; 

 used, the marks should be put on the side tube is made to 



by the manufacturers, as the oper- hold 17 - 5 cc - of acid - 



ator in attempting to do so will be apt to weaken or break the 



bottles. 



CALIBRATION OP GLASSWARE. 



53. Test bottles. The Babcock milk test bottles are 

 so constructed that the scale of graduation on the neck 

 measures a volume of 2 cubic centimeters, between the 

 zero and the 10 per cent, marks (44). The standards 

 for test bottles and other Babcock glassware adopted by 

 the Association of Official Agricultural Chemists of 

 America are given at the close of this book (306). It 

 will be seen that the limit of error for test bottles is 

 one of the smallest graduations on the scale, or .2 per 



1 Maine experiment station, bull. 31. 



