Chemical Analysis of Milk and its Products. 227 



simple method for ascertaining whether milk, cream, 

 butter 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 paraphenylenediarnin-solution 

 (2 per cent. ) are added. The mixture is then shaken; if a 

 dark violet color appears at once, the milk has not been 

 heated, or at any rate not beyond 176 F. If a sample 

 of butter is to be examined, 25 grams are placed in a 

 small beaker and melted by being placed in water of 

 60 C. The clear butter fat is poured off, and the re- 

 maining liquid is diluted with an equal volume of water. 

 The mixture thus obtained is examined as in case of milk. 



286. Boiled milk. The preceding test will serve to 

 distinguish between raw and boiled milk, and also to 

 ascertain if milk has been adulterated with diluted con- 

 densed milk. To what extent such an adulteration can 

 be practiced without being detected by this or similar 

 tests, has not been determined, but if a control test be 

 made at the same time with a sample of milk of known 

 purity, a small admixture of boiled (or diluted con- 

 densed) milk can doubtless be detected. 1 



287. Gelatine in cream. This method of adulteration 

 is sometimes practiced in the city cream trade, to impart 

 stiffness and an appearance of richness to the cream. To 

 detect the gelatine, a quantity of the suspected cream is 

 mixed with warm water, and acetic acid is added to 

 precipitate the casein and fat (1.5 cc. of 10 per cent.- 



i See also Siats, Unters. landw. wicht. Stoffe, p. 60, and Molkerei-Ztg. 

 (Hildesheim), 1899, p. 677. 



