53° 



THE POPULAR SCIENCE MOXTHLY. 



these, it is an honest milk ; if it do not, it is adulterated." And gen- 

 erally, the analyst is not open to argument. He has implicit faith in 

 his hydrometer and analytical balance. 



It is the purpose of the present article to point out the adulterants 

 which are commonly found in milk, and to describe a simple method 

 of analysis which will give conclusive results even when practiced by 

 those having no great proficiency in the use of apparatus and reagents. 

 The complete chemical analysis of a sample of milk is an operation 

 which taxes the patience of even a trained chemist, and when accom- 

 plished, it has little value not possessed by the results obtained from 

 the more rapid methods used by the State analysts. It is commonly 

 believed that the list of adulterants at the disposal of the dairyman is 

 practically unlimited, but if one will pause a moment, and reflect that 

 the adulterant chosen must not affect the taste of the milk, or show 

 any tell-tale sediment on standing, he will see that the possibilities of 

 fraud are niuch smaller than at first suspected. Of all the adulterants, 

 water is the most popular the land over, since it costs nothing and 

 tells no tales unless questioned by an analyst. In addition to water, 

 it is not uncommon to find a milk "doctored" by the use of preserva- 

 tive salts, such as borax or bicarbonate of soda, and colored to an 

 ideal cream tint by means of a little burnt sugar or vegetable coloring- 

 matter. 



In the State laboratories, it is generally required that determina- 

 tions shall be made of the specific gravity, the amount of cream, total 

 solids, fat, mineral salts, and water. Mr. Sharpies, public analyst for 

 Massachusetts, recommends also the determination of the amount of 

 sugar in the milk in order to place its quality beyond peradventure. 

 Most analysts, however, do not regard this determination as necessary. 

 As it is our object to make the analytical process as simple as possible, 

 and to bring it within reach of all readers having some delicacy of 

 touch, whether they be chemists or not, we shall only describe those 

 determinations generally considered essential, and then specify which 

 of these will suffice in most cases to establish the quality of the sample 

 under consideration. 



The first requisite is to decide upon a standard of purity. Opinions 

 differ as to what should be considered a normal milk. The chief dis- 

 crepancy lies in the amount of total solids which it should contain. 

 In England the standard in this respect is rather low, only 11 "5 per 

 cent of total solids being required. In Massachusetts, on the other 

 hand, the legal standard exceeds even the generosity of Nature, as it 

 calls for 13 per cent, when milk drawn directly from the cow, and 

 therefore free from any possibility of dilution, frequently shows but 

 a little over 12. 



The following abbreviated table will give the composition of aver- 

 age milk, and will serve as a standard for comparison when the results 

 of any particular analysis have been obtained : 



