LATENT AND SPECIFIC HEAT. 



335 



FIG. 254. 



Crystals of ice 



latent heat; of kinetic into potential energy. We may 

 represent, for instance, the va- 

 porization of water as follows : 

 Steam at 100 C. = water 

 at 100 C. + latent heat of 

 steam. 



(a.) The cryophorus, shown in 

 Fig. 254, consists of a bent tube 

 and two bulbs containing a small 

 quantity of water. The air is re- 

 moved by briskly boiling the water. 

 The tube is sealed while the steam 

 is escaping. The instrument thus 

 contains only water and aqueous 

 vapor. When the liquid is poured 

 into B, and A is placed in a freez- 

 ing mixture, the vapor is largely 

 condensed in A while more is rapidly formed in B. 

 soon form on the surface of the water in B. 



(b.) Wet a block of wood and place a watch crystal upon it. A 

 film of water may be seen under the central part of the glass. Half 

 fill the crystal with sulphuric ether and rapidly evaporate it by 

 blowing over its surface a stream of air from a small bellows. So 

 much heat is rendered latent in the vaporization that the watch 

 crystal is firmly frozen to the wooden block. 



527. Condensation of Gases. Gases may be 

 condensed by union with some liquid or solid, by cold or 

 by pressure. It has been recently shown that any known 

 gas may be liquefied by cold and pressure. In any case, 

 the condensation of a gas renders sensible a large 

 amount of heat. 



(a.} Sulphurous oxide (S0 2 ) previously dried, is easily liquefied 

 by passing it through a U-tube immersed in a freezing mixture. 

 When some of this liquid is placed upon mercury in a small capsule 

 and rapidly evaporated by blowing over it a stream of air from a 

 bellows, the mercury is frozen (497). 



