192 MILK 



(ii.) The removal of cream. 



(iii.) The addition of calcium saccharate (employed to increase 



the viscosity, and hence give the appearance of richness 



in cream), 

 (iv.) The addition of artificial colouring matter. 



The first two methods of falsification, being those of which the 

 detection is most important, will alone be dealt with here. 



The density of pure fresh milk being on the average 1032, 

 while the density of the fat globules is about -86, it follows that the 

 removal of cream will increase the density, while the addition of 

 water will decrease it. It is obvious, therefore, that by the 

 simultaneous removal of cream and addition of water in correct 

 proportion, the density will remain unchanged, the increase by the 

 removal of fat being exactly balanced by the decrease following 

 the addition of water. 



The determination of the density alone, therefore, will not lead 

 to the detection of any such adulteration. 



185. Change in Density of Milk on Skimming and 

 Diluting. 



About 200 C.C. of fresh milk are taken, and a small 

 proportion of cream thoroughly stirred in, in order to 

 render more apparent the effect of skimming on density. 



The milk is then divided into two equal portions, 

 one of which is allowed to stand for two to three hours 

 in order to permit of the rising to the surface of the 

 cream. The density of the other portion is determined, 

 preferably by means of Westphal's balance (177, p. 179). 



After two to three hours, as much of the cream as 

 possible is removed from the surface of the first portion 

 by means of a pipette, the skim milk remaining 

 thoroughly mixed by pouring from one vessel to another, 

 and its density determined as before. It will be found 

 that the density has increased, owing to the removal 

 of the lighter fat globules. 



To 50 c.c. of the skim milk is then added i c.c. 

 (2 per cent.) of water, the whole thoroughly mixed, and 



