PROPERTIES OF WATER 41 



TABLE XVII 



VOLUME AND WEIGHT OF PURE WATER AT VARIOUS TEMPERATURES 

 (From Marks and Davis) 



Latent Heat. This is the heat which apparently disappears 

 in producing some change in the conditions of a body without 

 increasing its temperature. To transform ice water and vapor 

 or steam from one state to the other, it is only necessary to supply 

 a certain quantity of heat energy, 460 F. being the absolute 

 zero of temperature. 



Thus in melting 1 pound of ice into water at 32 F., about 142 

 heat-units are absorbed and become latent, while in freezing one 

 pound of water into ice a like quantity of heat is given out to the 

 surrounding medium. 



Latent heat is not lost, but reappears whenever the substances 

 pass through a reverse cycle, from a gaseous to a liquid, or from a 

 liquid to a solid state. It may, therefore, be considered as the 

 heat which apparently disappears, or is lost to the thermometric 



