446 J. W. Gibbs—Hquilibrium of Heterogeneous Substances. 
bodies which differ only in size and form being regarded as 
ifferent examples of the same phase. Phases which can 
exist together, the dividing surfaces being plain, in an equi- 
librium which does not depend upon passive resistances to 
ni, 
change, are called coéaxiste 
d, : : 
such as —> may be expressed in terms of the entropies and 
EE, Bet RO SS 
dt v'—v" t(v’—v’')’ 
in which v’, v’, 7’, 7’, denote the volumes and entropies of a 
given quantity of the substance in the two phases, and Q the 
two pairs of coéxistent phases. 
If the temperature of three coéxistent phases of three compo- 
fe 25 
Nid SARs 
