THERMODYNAMICS OF ATMOSPHERE VON BEZOLD 251 



prevail after the dissipation of the supersaturation will be found by 



1 

 drawing through F t a straight line making an angle a = tg l — — if 



1 



the temperatures are above freezing, but a* =tg 1 ^Tq ^ the tem- 

 peratures are below freezing. 



The abscissa O T 2 of the intersection F 2 of this straight line with 

 the curve of saturation F' F' will be the desired temperature t 2 . 



The graphic construction just given may also be applied with a 

 slight but very important modification to the case now under con- 

 sideration. 



In the investigation above mentioned it was assumed that the 

 pressure remains constant since the assumption of supersaturation 

 served only as a numerical artifice, when the actual process must go 

 on gradually, and therefore the expansion due to the rise in tempera- 

 ture can also follow quietly. Therefore the adopted value of the ther- 

 mal capacity of air was that for constant pressure. 



Now, on the other hand, emphasis is laid on the assumption that 

 the disruption takes place so rapidly that the volume is to be con- 

 sidered as constant at first, so that the rise in temperature must 

 make itself felt as a change in pressure. 



Of course an equilibrium must eventually be attained, the air 

 must expand until its pressure comes into equilibrium with that 

 of the surrounding atmosphere, which process must again cause a 

 cooling. 



Therefore, whereas corresponding to the problem previously dis- 

 cussed, Ave had 



1000 c 

 tga = - 

 r 



for which we may now more appropriately write 



1000c„ 

 tg a v = 



where the subscript p indicates that we treat of constant pressure, 

 now, on the other hand, for the present case we introduce the angle 

 <x v for which we have the equation 



1000 c,, 

 tg <*v = - 



where c v is the specific heat of moist air under constant volume. 



