164 



BUTLER 



AHT. D 



Ss to the two coexistent phases containing Si and S2, we shall 

 obtain a series of two coexistent ternary phases, terminating in 

 a phase at which the two phases become identical. 



Let n be the number of independently variable components. 

 According to the phase rule, a pair of coexistent phases has n 

 degrees of freedom, i.e., is capable of n independent variations. 

 Thus, in the case of phenol and water, a pair of coexistent 

 phases can be varied independently in two ways, i.e., we can 

 vary both the temperature and the pressure without making 

 one phase disappear. Now if we keep the pressure constant 



Phenol % 

 Fig. 8 



WO 



and vary the temperature, we shall obtain a series of coexisting 

 phases terminating in the critical phase. At a slightly different 

 pressure there is a similar series of coexisting phases, terminating 

 in a slightly different critical phase. It is evident that the 

 number of independent variations of which the critical phase is 

 capable is one less than that of the two coexistent phases, i.e., 

 the number of independent variations of a critical phase, while 

 remaining as such, is n — 1. 



36. Conditions in Regard to Stability of Critical Phases. "The 

 quantities, /, p, /xi, M2, • ■ Mn have the same value in two co- 

 existent phases, but the ratios of the quantities 17, v, mi, m^, 



