MILK INSPECTION 



193 



Milk which has been either watered or skimmed, or both wat- 

 ered and skimmed, is considered according to law to be adulterated 

 and is the commonest form of adulteration. To determine whether 

 milk has been watered or skimmed (p. 204) three determinations are 

 necessary : viz., the determination of the total solids in milk ; fat ; and 

 the specific gravity. For the determination of the specific gravity 

 and approximate determination of milk solids, see pp. 197-203. The 

 determination of the fat alone is usually sufficient to estimate the 

 quality of milk for the farmer who does not adulterate his milk. 



Fig- 54- 



Small Babcock machine, with other necessary paraphernalia. 



The methods for determining accurately the amount of fat* 

 in milk are based upon centrifugal separation of milk. The theory 

 of these methods depends upon the fact that when milk is whirled 

 at a rapid rate — several thousand revolutions per minute — the 

 heavier portions of the milk are thrown outward, leaving the 

 lighter or fatty portions nearer the center of the whirling body. 

 The method of Dr. S. M. Babcock is the one in general use. 



The milk is measured in a suitable bottle and an equal volume 

 of sulphuric acid is added which dissolves the casein or curd of milk 

 and liberates the fat. 'The bottle is then whirled at a high speed, 

 allowing the fat to come to the top of the bottle — that is, as the 



* For approximate determination of fat and solids in milk, see p. 204. 



