112 Relation of Temperature and Molecular Attraction. 



Table III. 



„ hexane 



,, heptane 



,, oetane 



Hexam ethylene 



Benzene 



Fluor-benzene 



Chlor-benzene 



Brom-benzene 



Iodo-benzene 



Carbon tetrachloride 



Stannic chloride 



Methyl formate 



Ethyl formate 



Methyl acetate 



Propyl formate 



Ethyl acetate 



Methyl propionate 



Propyl acetate 



Ethyl propionate .. 



Methyl buty rate .. 



Methyl isobutyrate 



The relations are, however, not so simple as the above 

 argument would seem to indicate. For equation 21 can be 

 immediately obtained by combining equation 1 and the 



relation of Dieterici, X = CRT In t^, and obtaining the limit 



of the resulting equation at the critical temperature. Thus 

 we have, when v and V denote volumes of one gram of liquid 

 and vapour respectively : 



Kj ~ RTlnV/v ~ET lnV/^V^ + V^^+V 1 ' 3 ^' [ } 

 which at the critical temperature becomes 

 fi'Y c p'*/~d c 



C: 



iu/jl' s/d c 



3RT c Y c 4 /3 ~ 3RT C ~ 3 x 1-9861T/ 



(23) 



Now the kinetic energy, E 7o of the molecules of one gram 

 of a substance at the critical temperature is 



E*=3/2RT C =2-979 T calories, 



(24) 



