83 



Good market milk should have a specific gravity ranging from 

 1.029 to 1.033 ('29 to 33°). A specific gravity differing from this 

 may indicate either skimming or watering, and in such cases the 

 dairy milk supply should be investigated. 



The simple determination of the specific gravity above is, how- 

 ever, not decisive. Milk consists of substances which are dissolved 

 in water, and which increase its specific weight, and suspended fat, 

 which decreases its specific weight. A skimmed milk will, there- 

 fore, be heavier, and when adulterated with water, may have the 

 same specific gravity as a milk which is rich in cream. To decide 

 in such cases, it becomes, therefore, necessary to make an additional 

 determination of the quantity of fat present. 



B. — Examination of skimmed m.ilk : The milk under in- 

 vestigation, is brought into a wide vessel (tea cup shape), and 

 allowed to remain in a cool place (to prevent souring) for 24 

 hours. The cream which has collected on the surface, is then care- 

 fully removed, and the specific gravity of the remainder deter- 

 mined. For temperature corrections the second table (for skimmed 

 milk) should be employed. 



Unadulterated skimmed milk should have a specific gravity 

 ranging from 1.032 to 1.036 (32 to 36°) ; specific gravities under 

 1.032 indicate adulteration with water. 



On the basis of this observation Quevenne has given the follow- 

 ing table : 



Schrceder and Dietzel found that the specific gravity of the 

 serum of coagulated milk may likewise be used as an indicator for 

 the adulteration with water. A specific gravity less than 1.026 

 indicates adulteration with water. Further investigations regard- 

 ing this point are greatly to be desired. 



The fact that milk, after s^^ch investigations as have been 

 described, does not appear normal, may indicate adulteration, but 



