226 Testing Milk and Its Products. 



whey must be clear; it is cooled to 15 C. and its 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 water- 

 ing. An addition of 4 per ct. of water lowers the sp. gr. 

 of the whey about 1 lactometer degree. 1 



284. Detection of coloring matter. Milk which has 

 been watered or skimmed, or both, is sometimes further 

 adulterated by unscrupulous milk peddlers through the 

 addition 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 

 foreign coloring matter in milk is easily shown by shak- 

 ing 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 added; 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- 

 chromates 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. 



285. Detection of pasteurized milk or cream. Prof. 

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



i Siats, Unters. landw. wicht. Stoffe, p. 88. 

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

 340th report, Copenhagen experiment station. 



