70 



DETECTION OF ADUL,TERATIONS. 



Condition of tile Sample. 



Pure milk 



loo parts milk + lo parts water. . 

 100 parts milk -)- 20 parts water. . 

 100 parts milk + 30 parts water. . 



Density 

 at 15° C 



1.0300 

 1.027s 

 1.025 1 

 1.0230 



Total dry mat- 

 ter per liter. 



70.0 grams 

 64.0 " 

 S90 " 



54.5 " 



(3) By Beckman's method the freezing point of the 

 milk is determined. The results are not influenced by the 

 fats present, but are dependent upon the water content. 

 Normal milk freezes at — 0.554 degrees C. (average). 

 The lowering of the freezing point below that of water 

 is proportional to the concentration. It is lowered about 

 one-half the above number by diluting the milk with an 

 equal volume of water. The sample in question is 

 brought to the freezing point by means of a mixture of 

 ice and salt. A similar test is carried on with a sample 

 of distilled water. The difference in the observed freez- 

 ing points indicates the quality of the milk. An addition 

 of 10 per cent of water produces a diminution of only 

 0.055 degrees. 



From the results of a large number of analyses an 

 average normal number has been established for the 

 amount of each of the constituents of milk. By com- 

 paring other analyses with these figures adulteration may 

 be often exposed. For example, if the fat content of the 

 dried matter in milk is found to be less than 27.6 per cent 

 and the specific gravity of the same less than 1.335, there 

 is but little doubt of falsification (Herz). The nitrogen 

 content of unadulterated milk should never be less than 

 0.5 per cent;* the ash never less than 0.7 per cent. The 

 relation of ash to the dry matter, minus fat, varies from 



*Resiilts of 15,000 analyses. 



