COMPOSITION OF MILK. 47 



The boiling point of milk is slightly higher than 

 that of water, and it freezes at a slightly lower tem- 

 perature. Boiling imparts a cooked flavor to milk. 

 When frozen the richer portions are usually in the 

 unfrozen part. This is not so if a thick cream forms 

 on the milk before freezing takes place. 



Milk is at its maximum density at a fraction of a 

 degree above freezing point. The expansion and 

 contraction of milk does not occur at the same rate 

 at all temperatures. When heated, milk becomes less 

 viscous, will flow faster, and the cream will separate 

 more readily. 



Its power to absorb heat is less than that of water. 

 Electric currents, so far as known, have little effect on 

 milk. The souring of milk during thunder-storms 

 is not due to the excess of electricity, but to the fact 

 that atmospheric conditions are favorable at this time 

 for the growth of the lactic acid germs which cause 

 souring. 



