THE TESTING OF MILK AND CREAM 105 



capacity, shall cause a deflection of the pointer of at least one division 

 on the graduation. 



Weights, 9 gram weights for 9-gram cream test bottles and 18 gram 

 weights for 18-gram cream test bottles, preferably stamped correct 

 by the U. S. or State Bureau of Standards. 



Tester. Standard Babcock test centrifuge and speed indicator. 



Dividers, for measuring fat column. 



Water bath for cream samples, with proper arrangement for regulating 

 and recording temperature of samples. 



Water bath for test bottles, of sufficient size and with necessary equip- 

 ment to insure proper control of temperature. The following dimen- 

 sions for a twenty-four (24) bottle water bath are recommended : 

 Metal box, 14" long, 11" wide and 8" deep and equipped with a 

 bottle basket 9" long and 6" wide, capacity 24 bottles, a steam and 

 water inlet, a drain, a thermometer holder with thermometer. 



Commercial Sulfuric Acid, specific gravity 1.82 to 1.83. 



Glymol, or white mineral oil, high grade. 



ACCURACY OF THE GLASSWARE 



It is essential that the graduations on the test bottles and 

 pipettes be as accurate as possible. Many states require that 

 all Babcock glassware be calibrated by a state official before it 

 can be used in commercial work. Several methods have been 

 devised for this work. A simple method is thus described by 

 Van Slyke : 1 



"The quickest method of testing the accuracy of the scale 

 of a test bottle is to use a special device, which is essentially 

 a simple brass plunger (Fig. 5). This instrument is divided 

 into two equal portions, each part being made of such a size 

 as to displace exactly one cubic centimeter of liquid. This 

 bottle-tester is used as follows : The test bottle is filled to the 

 zero mark with milk, or one may use water or, better, wood 

 alcohol, imparting color to the water -or alcohol by adding 

 some black aniline or carmine ink. Fill the bottle nearly to the 

 zero mark and then finish with a pipette or dropper, adding a 



1 Modern Methods of Testing Milk and Milk Products, p. 45. 

 Orange Judd Co. 



