42 ANALYTICAL PROCESSES. 



not suffice to detect adulteration. Taken in conjuction 

 with either the figure for fat or for total solids, the 

 specific gravity becomes of direct value, and furnishes 

 a means for determining, by calculation, the remaining 

 datum . 



For milk control in dairies, etc., it will suffice to take 

 the specific gravity by the lactodensimeter (see page 16) 

 and the fat by the Leffmann-Beam method. From the 

 figures thus obtained the total solids can be ascertained 

 by Hehner & Richmond's table (Table B) or Rich- 

 mond's slide-rule. 



Various substances are added to milk to conceal 

 adulteration or inferiority in quality. The most fre- 

 quently employed are coloring matters. Sugar, salt, 

 starch and calf's brain have been added to milk, but 

 are of infrequent occurence. It has occasionally 

 been stated that chalk has been added, but this is ob- 

 viously unlikely. The. coloring matters most frequently 

 employed are annatto, caramel, saffron, carotin and 

 occasionally turmeric and certain coal-tar colors. 



Annatto is easily detected by rendering the sample 

 slightly alkaline by the addition of sodium acid carbon- 

 ate, immersing in it a slip of filter paper and allow- 

 ing it to remain over night. The presence of annatto 

 will be indicated by a distinct reddish-yellow tinge 

 to the paper. 



Coal-tar colors are detected by adding to the milk 

 ammonium hydroxid and allowing a piece of white 

 wool to remain in it over night. The dye is taken up 

 by the wool, which acquires a yellow tinge. When 



