248 Testing Milk and Its Products. 



293. Detection of coloring matter. Milk which has 

 been watered or 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 added; natural fresh 

 milk will -give a colorless ether solution. 



A method gived by Wallace^ is claimed to detect one 

 part of coloring matter in 100,000 of milk. 



Inorganic coloring matter like chromates and bi-ehro- 

 mates have, although fortunately rarely, been used to 

 impart a rich color to adulterated milk or poor cream. 

 Chrcmates 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,^ in 1898, published a 

 simple method for ascertaining whether milk, cream, 

 or other dairy products have been heated to at least 

 176° F. (80° C). The test is made as follows: A 

 teaspoonful of the milk is poured into a test tube, and 

 1 drop of a weak solution of peroxid of hydrogen (2 

 per cent.) and 2 drops of a paraphenylenediamin-solu- 



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

 ' 40th report, Copenhagen experiment station. 



