244 Testing Milk and Its Products. 



sp. gr. determined. The sp. gr. of whey from normal milk ob- 

 tained in the manner given will range between 1.027 and 1.031. 

 A sp. gr. of 1.026 or below indicates watering. An addition of 

 4 per cent, of water lowers the sp. gr. of the whey about 1 lac- 

 tometer degree. 1 



293. Detection of coloring matter. Milk which has 

 been watered cr skimmed, or both, is sometimes further 

 adulterated by unscrupulous milk dealers by an addi- 

 tion of a small quantity of cheese color; this will mix 

 thoroughly with the milk, and, if added judiciously, will 

 impart a rich cream color to it. The presence of for- 

 eign coloring matter in milk is easily shown by shaking 

 10 cc. of the milk with an equal quantity of ether; on 

 standing, a clear ether solution will rise to the surface; 

 if artificial coloring matter has been added to the milk, 

 the solution will be yellow colored, the intensity of the 

 color indicating the quantity addded; natural fresh 

 milk will give a colorless ether solution. 



A method given by Wallace 2 is claimed to detect one 

 part of coloring matter in 100,000 of milk. 



Inorganic coloring matter like chromates and bi-chro- 

 mates have, although fortunately rarely, been used to 

 impart a rich color to adulterated milk or poor cream. 

 Chromates may be detected by the reddish yellow color 

 produced when a little 2 per cent. -silver nitrate solution 

 is added to a few cubic centimeters of the milk. 



294. Detection of pasteurized milk or cream. Prof. 

 Storch, of Copenhagen, Denmark, 3 in 1898, published a 

 simple method for ascertaining whether milk, cream, 



1 Slats, Unters. landw. wicht. Stoffe, p. 88. 



2 N. J. Dairy Commissioner, report. 1896, p. 36. 

 8 40th report, Copenhagen experiment station. 



