26 QUESTIONS AND ANSWERS 



How does the fat affect the specific gravity of 

 milk? 

 The specific gravity of milk fat being only a little 

 more than .9, it is lighter than the other constituents 

 and tends to lower the specific gravity. 



Why is it that milks, naturally rich in fat, have a 



higher specific gravity than milks naturally 



poor in fat? 



Pure milks, rich in fat, contain larger percentages 



of solids not fat than do those of low fat content. 



Take, for example, samples of milk of the following 



composition : 



Board of health 

 Fat Solids not fat lactometer reading 



I 3.9 8.6 108. 



2 4.9 9.1 III. 



No. 2 contains i per cent more fat and .5 of 

 I per cent more solids not fat than does No. i. 

 One per cent of fat lowers the lactometer read- 

 ing practically 3 degrees, while .5 of i per cent 

 of solids not fat raises the lactometer at least 6 

 degrees. Thus we have a final lactometer reading 

 of III in the richer milk. 



What is the specific gravity of the milk solids? 



The solids of normal milk have a specific gravity 

 between 1.25 and 1.34, the average being about 

 1.30. 



What is the specific gravity of the solids not fat? 



The solids not fat are made up of casein, albumin, 

 sugar, and mineral matter, and have a specific 

 gravity of about 1.50. 



