TESTING MILK FOR ADULTERATIONS I37 



Standard, may be calculated by the following rule: 

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

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

 tract this from lOo; or expressed as a formula: 



The per cent, of fat removed=ioo — ^ x ^"Q 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 16.6 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. 



