232 Milk Inspection. 



ruination of the specific gravity, which is usually 1.026 to 1.027. 

 In applying this method it may become necessary to use larger 

 amounts of serum. Differences of about 0.0025 in the specific 

 gravity indicate mixing with about 10% of water. 



The positive demonstration of nitrates in milk is always a 

 proof that the milk has been watered and with water that should 

 be considered as objectionable as drinking water, or that has been 

 used for the rinsing of the milk containers, and which according 

 to its quality must be considered as impure. Milk which gives the 

 nitrate reaction should therefore be considered not only as adul- 

 terated but also as being spoiled in the sense of the pure food 

 law and even as injurious to health. The nitrate test may become 

 of great importance for the conviction of certain persons, when 

 for instance the water of the well at the barn contains nitrates, 

 while the one at the farmhouse has no nitrates and vice versa. 

 According to Rothenfusser the nitrate test is a substantiating 

 proof of great importance. Milk samples contaminated with 

 manure and litter do not give the nitrate test. 



Nitrates and nitrites do not occur in milk of animals fed and 

 cared for in the usual manner on the farm. Rothenfusser ascer- 

 tained that the unavoidable residue of water used in rinsing the 

 milk containers represents only a tenth or a twentieth part of the 

 amount of water, which is necessary to make a 1% addition and 

 that the residue of water retained in the rinsed vessel must possess 

 the qualities of ditch water in order to be capable of adding to 

 the milk a demonstrable amount of nitrates. According to Rothen- 

 fusser the test may be carried out to the best advantage, by placing 

 into small, flat, white porcelain vessels 2 c. c. of pure sulphuric 

 acid of a specific gravity of 1.84, over which a small amount of 

 crystallized diphenylamin is sprinkled from a sprinkling cylinder 

 (a reagent tube with a perforated cork stopper, into which a short 

 glass tube of about 3 mm. inside diameter is inserted). 



Then a small quantity of chloride of calcium serum of the 

 milk to be examined is allowed to flow in from the edges of the 

 vessel. The appearance of the grayish-blue clouds and stripes in 

 the fluid indicates the presence of nitric acid in the milk. 



