LATENT AND SPECIFIC HEAT. 337 



ture is eighty times as great as the heat required 

 to warm the same quantity of water one centi- 

 grade degree. 



(a.) Because of this great latent heat of water, the processes of 

 melting ice and freezing water are necessarily slow. Otherwise, the 

 waters of our northern lakes might freeze to the bottom in a single 

 night, while "the hut of the Esquimaux would vanish like a house 

 in a pantomime," or all the snows of winter be melted in a single 

 day with inundation and destruction. 



529. The Latent Heat of Steam. Experiment 

 has shown that the amount of heat necessary to evaporate 

 one pound of water would suffice to raise the temperature 

 of 537 pounds of water 1 C. Hence we say that the latent 

 heat of steam is 537 C. (or 967 F.). This means that the 

 amount of heat required to evaporate a quantity 

 of water without changing its temperature is 537 

 times as great as the heat required to warm the 

 same quantity of water one centigrade degree. 



(a.) When a pound of steam is condensed, 537 heat units (pound- 

 centigrade) are liberated. In this we see an explanation of the 

 familiar fact that scalding t>y steam is so painfully severe. Were 

 it not for the latent heat of steam, when water reached its boiling 

 point it would instantly flash into steam with tremendous explosion. 



530. Problems and Solutions. (1.) How many pounds 

 of ice at C. can be melted by 1 pound of steam at 100 C. ? One 

 pound of steam at 100 C., in condensing to water at the same tem- 

 perature, parts with all its latent heat, or 537 heat units. The 

 pound of water thus formed can give out 100 more heat units. 

 Hence, the whole number of heat units given out by the steam in 

 changing to water at C., the temperature at which it can no longer 

 melt ice, is 537 + 100 = 637. 



Let x = the number of pounds of ice that can be melted. Each 

 pound of ice melted will require 80 heat units. Hence, 80# the 

 number of heat units necessary. The heat to melt the ice must 

 come from the steam. 



Therefore 80z = 637. /. x = 7.96 + Ibs. Ana. 



15 



