TESTING MILK FOR ADULTERATIONS 145 



standard, may be calculated by the following rule : 

 Multiply the per cent, of fat in the milk by 100, di- 

 vide the result by the legal standard for fat and sub- 

 tract this from 100; or expressed as a formula: 



The per cent, of fat removed=ioo ?_><_ This 

 formula is true only for milks originally containing 3 

 per cent, of fat and so its results are generally much 

 below the truth. For example, in a milk containing 

 originally 5 per cent, of fat, which has been skimmed 

 to 2.50 per cent., thus removing 50 per cent, of the 

 fat in the milk, the above formula would indicate that 

 only 1 6.6 per cent, of the fat had been removed. In 

 most cases results nearer the actual truth are given 

 by substituting 3.75 for 3 in the formula. 



GENERAL METHOD FOR JUDGING WATERED 

 AND SKIMMED MILK 



Having found in a sample of milk ( I ) the per cent, 

 of fat, (2) the specific gravity of the milk and (3) of 

 the milk-solids, (4) the per cent, of solids, and (5) of 

 solids-not-fat, one may arrive at fairly safe conclu- 

 sions in regard to the watering and skimming by 

 making comparison with the percentages of constitu- 

 ents present in average normal milk. In forming such 

 conclusions, the following facts should be kept in 

 mind: 



1. Water has a lower specific gravity than milk. 



2. Watering milk decreases (a) the lactometer read- 

 ing, (b) the fat, (c) total solids, and (d) solids-not-fat. 



3. Water has a higher specific gravity than milk-fat. 



