REDUCTION OF HUMIDITY DATA— VON BEZOLD 329 



Since the quantities x and y are in general very small and scarcely 

 ever exceed the value 0.03 but are generally much smaller, there- 

 fore they are never very different from each other and for a rough 

 approximation may be considered briefly as equal to each other. 



Now in order to put the meaning of the specific humidity and the 

 mixing ratio in a very clear light it seems appropriate to investigate 

 how the other quantities vary when the former is constant. 



To this end write equation (3) in the form 



£ ^x + 0.623 



and substitute this in equation (1), then we obtain 



/? x 



1 + at ' x +0.623 



/ = 1.060 



This equation shows that with constant pressure but variable 

 temperature, the absolute humidity experiences changes even when 

 the composition of the air remains constant. 



We get the best idea of the matter if we assume that we change 

 the mixture from an initial condition, in which the appropriate 

 quantities have the subscript index 1, over into another for which 

 we use the subscript 2. 



If then we assume 



it results that 



but 



A- A 



t 2 > t x 



€■> = £1 



f 2 < f, and R 2 < R, 



If, on the other hand, we imagine that the volume remains 

 unchanged, then according to the well-known law of Mariotte-Gay- 

 Lussac we have the relation 



ft _ 273 + t 2 

 ft _ 273T7, 



or 



