44 



Biological, Chemical and Physical Characteristics of Milk. 



or establishment of the addition of water, provided that the serum 

 is always prepared in the same way. Ackermann, Mai and Roth- 

 enfusser have in their fundamental works, determined the practi- 

 cal importance of the polarization of the proteid-free serum, and 

 have proved that with the polarization of the chloride of calcium 

 serum we possess means which are better adapted than any other 

 to the detection of the adulteration of milk by water. Refrac- 

 tion is the most valuable accessory to the various methods of tests 

 of recent times. 



Ackermann found in 2,800 samples of normal milk, variations 

 in the scale division of Zeiss 's immersion ref ractometer, from 38 . 5 

 to 40.5. 



Even slight additions of water reduce the refraction con- 

 siderably; the addition of 5% of water results in a 1.3 lowering of 

 the scale division, while 10% lowers it 2.3. 



According to Mai and Rothenfusser the original refraction of 

 39 scale divisions is lowered to a refraction of : 



37.9 with about 4% addition of water 

 37.7 " " 5% " < 



37.5 



37.3 



37.1 



36.9 



36.7 



36.5 



36.3 



36.1 



35.9 



35.7 



35.5 



35.3 



35.1 



35.0 



34.8 



34.0 



33.3 



32.6 



32. 



30.9 



070 



7% 

 8% 



10% 

 11% 



12% 

 13% 



14% 



16% 



17% 

 18% 

 19% 

 20% 

 25% 

 30% 

 35% 

 40% 

 50% 



It 

 (t 



1 1 

 14 



1 1 

 (t 



1 1 

 1 1 

 1 1 

 

 i I 

 1 1 

 t < 

 (4 

 it 

 it 

 it 

 1 1 

 < t 

 1 1 

 ( l 



In the establishment of the refraction index of the chloride of 

 calcium serum it was also discovered that it is impossible to estab- 

 lish normal values for the chloride of calcium serum, as well as for 

 other constituents of milk. Mai and Rothenfusser also estab- 

 lished the general rule for milk, that only in the presence of rigor- 

 ous controls of the same origin can the addition of water be 

 satisfactorily determined, and the extent of the adulteration 

 established. 



