* 



I CHEMICAL TESTING OF MILK AND 

 CREAM. 1 



CONTENTS. 



Page. 



Chemical nature of milk 3 



Testing for fat 5 



Testing milk for fat 5 



The Babcock test 7 



Testing cream for fat 18 



Testing skim milk for fat 23 



Testing buttermilk and whey for fat 25 



Preserving samples 25 



Cleaning the test bottles 25 



Determination of total solids in milk 26 



Determination of specific gravity of milk 30 



Calculating total solids by formula 32 



Determination of acidity of milk and cream 36 



Manns's acidity test 37 



Detection of preservatives 38 



Chemicals and apparatus used in the chemical 



analysis of milk and cream 40 



Comparison of metric and customary weights and 



measures 41 



Comparison of Fahrenheit and Centigrade ther- 

 mometer scales 41 



CHEMICAL NATURE OF MILK. 



In order to follow intelligently the methods for testing 

 milk and cream some knowledge of the chemistry of milk 

 is essential. From a chemical standpoint milk is a very 

 complex substance. The component parts may, however, 



1 This is a reprint, with slight revision, of a publication issued Feb- 

 ruary 17, 1916, under the same title. In its preparation free use has been 

 made of the various publications on the subject, particularly "Testing 

 Milk and Its Products," by E. H. Farringtonand*F. W. Woll (Madison, 

 Wis., 1911), and "Modern Methods of Testing -Milk and Its Products," 

 by L. L. Van Slyke (New York, 1907). 

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