ADIABATIC CHANGES OF MOIST AIR NEUHOFF 439 



Hence as the equation of change for the mixture there follows: 

 dQ = (c' p + xc" p ) dZ - A (l +-\rT d ± . . . .(3) 



where Cp = 0.2375 indicates the specific heat of air and c p = 0.4805 

 the specific heat of aqueous vapor, both under constant pressure. 

 In the case of adiabatic changes the quantity dQ = o, hence after 

 separating the variables we obtain as the differential equation 

 of the adiabat 



d T I __ x\ dp 



„ dT ( x\ 



= (c p + x c p ) -y ■ - A [ 1 + £ J 



c p 



AR\ x J T p 



\ 1 + / 



£ 



P 



'V 



For brevity put 



v 

 A R 



1+, S \ 

 1 + x/e J 



then by integration we obtain 



log p/po = m l log T/T 



and also 



log p — nit log T = constant (4) 



= lo g Po - m i lo g T o 



as the equation of the adiabat for the dry stage. 



This equation is identical with Poisson's except that the factor 

 m has various values that depend upon the mixing ratio x of the 

 air. After substituting the numerical values we obtain 



.... (I + 2.023* 

 «. = 3.441 — 



\1 + 1-608 x 



In order to establish the numerical value of this factor and to 

 understand its influence on the result of our computation for 



