354 



KEYES 



ART. J 



The case of a pure liquid under pressure in excess of its vapor 

 pressure at constant temperature can be treated quite simply- 

 using equation [272], provided it is assumed that the neutral 

 ideal gas exerting the pressure on the liquid phase dissolves to a 

 negligible extent, and that it is at the same time completely 

 indifferent with respect to the vapor of the liquid. The latter 

 restriction means, of course, not only that there must be no 

 chemical action but also that the neutral gas must exert no 

 "solvent" action with respect to the vapor. 



For the vapor phase 



dv'\ 



(36) [272] 

 (37) 



(38) [272] 

 (39) 



But if equilibrium subsists, fx' = fx", and moreover for a single 

 pure phase, neglecting any possible complication due to the 

 dissolved neutral gas, 



and for the liquid phase 



\dm/p. 



dm 



[{v"sat. + ap)m] = v"sat. + ap, (40) 



where a is the compressibility of the liquid. Substituting 



— for I -— and mtegratmg from the normal saturation pres- 

 p \dm/p,t 



sure to the vapor pressure arising as a consequence of the changed 



potential of the compressed liquid in the case of the vapor, and 



from the normal saturation pressure to the pressure p of the 



neutral gas in the case of the right hand member, there is 



obtained 



log^ = ?^- (P - p,^,) + "1^ (P2 _ p2^„j . (41) 



Psat. at 2a t 



