i MILK 103 



It consists of a small box containing dilute formalin solution, 

 concentrated sulphuric acid, test-tubes, and a very dilute 

 solution of nitric acid. 



Fritzmann's test has the advantage over that of Soxhlet 

 that it can be applied directly to the milk and by anybody. 



Care must, however, be taken not to draw definite conclusions 

 from the results of the nitrate test. Many spring and tap 

 waters contain no nitrates, so that milk adulterated with such 

 water would not give the nitrate reaction. On the other hand, 

 the washing of the vessels with water containing a lot of 

 nitrates would cause the milk to react to the nitrate test, 

 although no adulteration had taken place. 



A positive result got by the nitrate test can only be 

 regarded as an indication that the milk is suspicious, and 

 must be carefully examined. Under no circumstances, how- 

 ever, should a positive result be regarded as a certain proof 

 that water has been added to the milk. 



2. Determination of the Specific Gravity, the Fat, and the 

 Total Solids. 



Fleischmann 1 has, with the help of very comprehensive and 

 accurate analytical data, constructed the formula which bears 

 his name, and which serves to calculate the amount of total 

 solids in milk if the specific gravity and the percentage of fat 

 are known. Provided the total solids and the specific gravity 

 are known, the amount of fat in a sample of milk can be deter- 

 mined. This formula, in which the specific gravity of the dry 

 matter free from fat (solids not fat) is taken to be 1*6007, is as 

 follows : 



. 1. 2./ + 2-665 



t = total solids expressed in percentages. 



/ = percentage of fat in milk. 



s = specific gravity of the milk at 15 C. 



If t and s are known, and f is to be calculated, this may be 

 done with the help of the formula : 



= 0-833. <-2-2 



1 Journal fur Landicirtschaft, 1885, Vol, XXXIII, p. 251. 



