6 DAIRY CHEMISTRY 



obtained in the pure state, it resembles in appearance 

 confectionery sugar, but not in taste. Milk sugar 

 takes an important part indirectly in butter and 

 cheese making, as it is the material from which the 

 acid is formed that sours the milk. The amount of 

 milk sugar or lactose in milk is quite constant, 

 ranging from 4.6 to 5.4 per cent. In average milk 

 it is the constituent which is present in the larg- 

 est amount of any of the milk solids. The part 

 which milk sugar takes in butter and cheese mak- 

 ing will be considered in other chapters of this 

 work. 



8. Ash. — When the milk solids are burned, there 

 is a small amount of grayish white ash obtained. 

 The ash content of milk is constant and varies but 

 little from three quarters of one per cent. Milk ash 

 is composed of common salt, and phosphates and 

 chlorids of potassium, calcium, and magnesium, to- 

 gether with small amounts of other minerals. A 

 portion of the phosphorus is in combination with the 

 casein. 



When milk is analyzed in the laboratory, the ash 

 is obtained by completely burning the milk solids at 

 a low temperature. The small dish containing the 

 milk solids (see section 3) is placed either over a 

 specially regulated flame or in a low-temperature 

 muftte furnace to completely burn the sugar, casein, 

 albumin, and fat without volatilizing any of the 

 mineral salts. The dish containing the milk ash 

 is then weighed and the per cent of ash determined. 



