( 492 ) 



rp I Vapour tension I Mol. vols, of the 



^*" j in m.m. Hg. I vapour in liters 



Fig. 5. 



/ /3€ t^c /^ /<^^' '/o f^^ 'p >''^ 



T 

 laximinn at 170° 



The figures 5 and 6 are graphical represeulatioiis of the pt- and 



the rt-cm-vQS. 



We see, that tlie niaxiinuni in the j)t-cuvve lies at al)ünt 170', 

 and that the niininiuni in the /V-eiirvL' lies at 101". The nia.xiniuni 

 in lig. 5 is therefore not found at the same temfjerature as the 

 niininiuni in tig. 6. (j). 403). 



Thai this must l)e the case can he easilv proved In applying the 

 ecpialion /'r=//7'. If we diflei-enliale this (Mpiatiou, we get: 



dv dT dp 



7 " ~t'~~p 



or 



dv ^ f ^ -^ '^J' 



dv ^ ■ 1 



For the minimum in the i'/-curve -= =r is therefore 



dl 



