CHAPTER XIII 



Methods of Testing Specific Gravity and Solids 

 of Milk by the Lactometer 



The specific gravity of milk may furnish important 

 information, which becomes of special value when 

 taken in connection with the amount of fat present. 

 Thus, with the data furnished by the specific gravity 

 and the per cent, of fat, we can easily calculate the 

 amount of solids in milk and the amount of solids- 

 not-fat. 



THE SPECIFIC GRAVITY OF MILK 



Definition of specific gravity. By the specific grav- 

 ity of milk, we mean the weight of a given bulk or 

 volume of milk as compared with the weight of an 

 equal volume of water at the same temperature. To 

 illustrate, suppose we have a vat which, when just full 

 of water, contains exactly 1,000 pounds of water at 

 60 F. Now, if we fill such a vat full of milk of aver- 

 age composition at the same temperature, this amount 

 of milk weighs 1,032 pounds. This is so because the 

 milk contains, in addition to the water in it, several 

 solid substances heavier than water. In this illustra- 

 tion we express the relation or ratio of the equal vol- 

 umes of water and milk by dividing 1,032 by 1,000; 

 the result, 1.032, is the specific gravity of the milk. 



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