948 Dr. S. A. Shorter : Contribution to the 



These equations determine the vapour pressure II and the 

 concentrations Si* and s 2 * as functions o£ s 1} s 2 , and 6. If we 

 differentiate these equations with respect to s^ and s 2 , we 

 obtain six equations containing the following quantities : — 



the twelve quantities, 



^— and^- of II, §!*, and s 2 * ? 

 OSi os 2 



which may be determined experimentally ; 



and the twelve differential coefficients, 



|£ and gg (,=0,1,2:^=1,2). 



The twelve differential coefficients are reducible to six by 

 means of equations (9), (10), (11) and the corresponding 

 equations relating to the vapour phase. The coefficients 

 may therefore be evaluated in terms of the experimental 

 magnitudes. Hence the experimental data relating to the 

 equilibrium suffice for the complete thermodynamical study 

 of the mixture. If one of the components is involatile, both 

 the number of equations and the number of differential 

 coefficients are reduced to four, so that the complete study 

 is still possible. If, however, only one component is volatile, 

 the complete study is not possible. 



Considerable simplification is introduced if it is assumed 

 that the mixture of vapours obeys the partial pressure law. 

 The equilibrium equations may then be written in the form 



A(*i,**n,0)=F o (IIo,0) .... (25) 



/ 1 ( 5l ,. 2 ,n^)=F 1 (n 1 ,^) .... (26) 

 / 2 (^* 2 ,n,0)=F 2 (ii 2 ,0), .... (27) 



where II; is the partial pressure and F; the chemical potential 

 of the vapour of C;. If in addition we neglect the specific 

 volumes of the liquid components in comparison with those 

 of the vapours, we may regard the chemical potentials of the 

 components in the liquid phase as independent of the pressure, 

 so that we obtain by differentiation 



M*,**^=V<(H*01^ (i = 0,l,2:>=l,2),(28) 



where Vi is the specific volume of the vapour of C,-, and p is 

 any pressure not too far removed from the vapour pressure. 



