( 470 ) 



been performed, equal to the product of the thermic pressure and 

 the volume which the molecule occupied in the phasis. 



And if a priori we should not be convinced of this, it would 

 appear as soon as the significance of ft = s — Tr])-\-pv is examined. 



The quantity, which must be equal for the two phases, we may 



denote 



E+pv 

 — V+ J, 



or according to the notation of Mr. Gibbs : 



in which Z is the function which Mr. Gibbs has called „heat 

 function for constant pressure" (Equilibrium of heterogeneous sub- 

 stances, p. 148). 

 To compare it with the equation of Prof. Boltzmann we put 



pv — € 2 e 



a / a \ 



If f = ,py — e = r(/>-)- —5- ) . 



V \ v~ J 



a 



The quantity p -\- —- , the sum of the external and molecular 



pressure we call "thermic pressure." 



a 

 If we put p -\ — = r T F not inquiring for the present into the 



form of F^ the above formula becomes 



2c rFvT-{-2s 



— Yj -\- r Fv -\ — - ^ — >? + 



T ' ' T 



Even in this form we see that the quantity rFTv^ which may 

 be considered as work of the thermic pressure, is of the same nature 

 as the quantity 2 e. 



This is still more evident, if we put F= and substitute- 



b V 

 rT-\-r T for r T. 



V — b V — b 



