46 PHYSICAL PROPERTIES AND COMPOSITION 



As an instance of this we will calculate the saturation 

 pressure of ether at 103. Since here 



T k = 467-4 ; P k = 27060 mm., 

 we have 



T 273 + 103 = . 8o5 . 

 T k 467-4 



Taking benzene as comparison substance it appears from 

 the preceding table that for 



T P 



^ = 0-805, -p-= 0-2064; 



Ik ** 



so that for ether 



P = 0-2064 x 27060 = 5590 mm. 

 According to Regnault, for ether 



Pioo = 4953-3' P uo = 6 2 14-63> 



and linear interpolation gives 



Pioa = 5332. 

 As a second instance we will calculate the boiling point 



of ether. Then 



P 760 Q 



-jr = - - = 0-0281 ; 

 P k 27060 



whence interpolating from the data for fluor-benzene as 

 standard substance 



0-0295 0-656 



0-0224 0.640 



T 



-- = 0-653 and T = 0.653 x 467.4 = 305 

 Tk 



i. e. on the centigrade scale 305 273 = 32, whilst 35 is 

 observed. 



B. Empirical Relations and Molecular Weight. 



Since the characteristic equation brings out insufficiently 

 the relations between pressure and temperature, we are 

 obliged either to restrict ourselves to direct use of the 

 numbers for a comparison body, or to express these by 



