PHYSICAL PROPERTIES OF MILK 101 



average value between 30° and 60° C. for four samples thus 

 treated was 0.507. At 30° C. it was 0.485 and at 60° C. 0.530. 



FREEZING POINT OF MILK 



Since the density of milk is greater than that of water, it 

 freezes at somewhat lower temperatures. The exact tempera- 

 ture at which milk will freeze is dependent on the relation 

 between the solids and the water it contains ; the higher the 

 percentage of solids present, the lower will be the temperature 

 required to freeze it. The freezing point for milk of average 

 composition is about 0.55° C. below that of water. The higher 

 the water-content, the more nearly will the freezing point ap- 

 proach that of water. 



ELECTRICAL RESISTANCE AND CONDUCTIVITY (Wilcox) 



The electrical conductivity of milk depends upon the degree 

 of dissociation of the salts which it carries in solution. The 

 resisting power of milk ranges between 180 and 210 ohms. If 

 water is added to milk, its resistance is increased. An accurate 

 determination of the amount of dilution cannot be made by an 

 electrical test for the reason that the resisting power of water 

 varies with its salt content. 



REFRACTIVE INDEX OF MILK (Wilcox) 



The refractive power of milk varies greatly according to the 

 composition. In normal milk the refractive index ranges from 

 1 .3470 to 1 .3515. A minimum of 1 .3435 is very rarely observed. 



