as a Standard of Electromotive Force. 



221 



Inspection of fig. 5 will suffice to show the possibility of 

 finding values of x and y which satisfy these conditions. 



Fig. 5. 



The same conclusion can be reached, less directly, by 

 considering the variations with c of the total thermo- 

 dynamical potentials f and f ' per 100 grams of all-fluid and 

 all-solid mixtures, remembering the relations 



d£/dc = fi b — fjL a and dgjdc = fib — /*/. 



In the system of fig. 5, therefore, coexistence of two phases 

 is possible when the liquid phase contains x per cent. B and 

 the solid phase y per cent. B. All mixtures containing between 

 x per cent, and y per cent, of B, and only those, can split into 

 two phases. 



Q2 



