ADULTERATIONS OF MILK 



219 



III. CONSTANTS OF MILK AND MILK SERUM. A WHOLE MILK SYSTEMATICALLY 

 WATERED (LEACH) 



35 c.c. of the serum to one of the beakers that accompanies the 

 control-temperature bath used in connection with the Zeiss im- 

 mersion refractometer, and take the refractometer reading at 

 exactly 20° C, using a thermometer graduated to tenths of a 

 degree. A reading below 39 indicates added water: between 39 

 and 40 the sample is suspicious." 



A test for nitrates in milk has been recommended for detect- 

 ing addition of water. Usually the water used on farms is derived 

 from deep wells, and these commonly contain nitrates. In pure 

 milk there are no nitrates, even, as has been shown by experi- 

 ments, if saltpeter is added to the cow's food in moderate quantity. 

 A simple test can be made in this manner: 2 c.c. pure sulphuric 

 acid are placed in a white evaporating dish and a few crystals of 

 diphenylamin dusted on the acid. Then a small amount of 

 milk serum, prepared with calcium chlorid, is poured down the 

 side of the dish. As the serum mixes with the acid bluish streaks 

 indicate the presence of nitrates. 



Detection of Thickening Agents 



When milk is watered, skimmed, or both watered and skimmed, 

 or even when it is naturally of low fat content, it is usually whiter 

 than milk with normal fat content and may be deficient in vis- 

 cosity. Consistency or viscosity may be restored by addition of 

 sucrate of lime or gelatin, the latter being not infrequently used 

 to thicken buttermilk in imitation of Bulgarian milk. Cane- 

 sugar is also added sometimes to increase the sohds and conceal 

 acidity. 



To detect cane-sugar in milk the following method can be 

 used: Mix 25 c.c. of milk or cream with 10 c.c. of a 5 per cent. 

 solution of uranium acetate, and filter after five minutes through 

 a folded filter. To the clear filtrate add 2 c.c. of a cold saturated 



